From the Gorgon's blood to Behring's Blutserumtherapie: A long path towards serum therapy

Summary

At the end of the 19th century medicine was turned upside down by the development of serum therapy, a great therapeutic revolution as was vaccination a few years earlier. Many serums were developed, the most famous being the German doctor Emil von Behring's diphtheria serum, which saved countless children's lives from this dreadful disease. The discovery of the serum therapy principle, allowed by the progressive understanding of humoral immunity, occurred both in Germany and France, almost at the same time. Interestingly, this principle arose from two different intellectual paths, reviving the age‐old opposition between mechanism and vitalism: while Behring came to this discovery reasoning as a chemist, French researchers Charles Richet and Jules Héricourt behaved as physiologists, focusing on the role of the host in the host‐pathogen interaction. However, we should maybe consider that serum therapy history begins much earlier. Great forerunners must not be forgotten, especially researchers who investigated the field of immunity as soon as in the very beginning of the microbiological revolution; but also many people throughout centuries who tried to cure diseases with blood: as a transfer of blood serum, serum therapy also lies in the tradition of blood transfusion.

1. INTRODUCTION

During the 1891 Christmas night, in a Berlin hospital, a young child who was dying from diphtheria had his life saved by a new, revolutionary cure. At his bedside, a doctor called Emil von Behring, who for the first time tried on a human being the antitoxic serum he had talked about in his Deutsche medizinische Wochenschrift article of December 1890. ¹ For years this legendary image stayed in people's minds: dreadful diphtheria, responsible for countless children's deaths, was defeated.

In medicine today, whereas monoclonal antibodies are widely developed, serum therapy, their ancestor, plays a minor role. Few serums are now used: anti‐venomous serums, anti‐thymocyte globulin, and specific immunoglobulins (like anti‐tetanus antitoxin, hepatitis B immune globulin or Rho [D] immune globulin). In our daily practice we could therefore easily forget how important serum therapy was at the time of its discovery, more than a century ago. Yet it was a genuine therapeutic revolution, as was the development of vaccination a few years before.

Such a great discovery did not come by itself, of course. It originated from lots of previous works and thoughts. As a transfer of immunity, we could imagine that serum therapy merely lay in the tradition of immune therapies and arose from the discoveries in that field, particularly vaccination. It is not that simple. As a transfer of blood serum, serum therapy was also an heir of blood transfusion attempts throughout centuries.

This article tries to investigate the steps which led to the discovery of serum therapy.

2. BLOOD AS A CURE: AN ANTIQUE FANTASY BECOMING REALITY

The idea of using blood for therapeutic purposes is very old. In Greek mythology, as reported by Pseudo‐Apollodorus in the third book of his Bibliotheca, Asclepius, founder God of medicine, was given a very special gift by Athena: the blood of Medusa, the Gorgon killed by Perseus. While blood from the monster's left veins was a deadly poison, the one from the right veins had the power to cure, and even to bring the dead back to life. Over‐valued in the Greco‐Roman Antiquity, despite the balanced approach of the Hippocratic school (which did not establish any hierarchy between the four humors), blood was given mystical qualities and supernatural powers. As the principle of life, it was offered to the dead and to the divinities in sacrifice; and Pliny the Elder reported in his Natural History that epileptic people went down in Roman amphitheaters to drink, from the wounds of dead gladiators, their still‐warm blood, “the very breath of life.” ² Bible also contributed to the mythification of blood. As noted by N.S.R. Maluf the Old Testament often refers to blood as “life of the body,” ³ and the New Testament portrays Jesus Christ's blood, poured out for the forgiveness of sins, as the new covenant between God and men.

Andreas Libavius (1546–1616) of Halle seems to be the first to detail the operation of blood transfusion in 1615. He pictured it as a “rejuvenating art”, which could impart to a cachectic old man “the fountain of life” thanks to the blood of a young healthy man. ³ The first established blood transfusions, however, occurred later in the 17th century, after William Harvey (1578–1657) had discovered the principle of blood circulation (Exercitatio anatomica de motu cordis et sanguinis in animalibus is published in 1628). In England Richard Lower (1631–1691) tried transfusions between animals in 1665 (similar experiences could have been led in Italy by Giovanni Colle and Francesco Folli, but there is no evidence about that). ⁴ Soon after, in 1667, the French Jean‐Baptiste Denis (c.1640–1704) carried out the first known transfusion (from lamb's blood) to a human being, in order to cure him from a prolonged fever. A few months later it was the turn of Lower, and for a while blood transfusion from animals to human beings became fashionable and used in various diseases in Europe. ³ Figure 1 How did people perceive blood transfusion at this time? Around the years 1667–1668 there was a great controversy between supporters and opponents of blood transfusion. ⁵ Supposed to compensate the blood loss after a hemorrhage or a bloodletting, or to correct alleged bad properties of the blood (heat, cold, thickness…), blood transfusion was mostly used in accordance with Galen's theories. ⁶ , ⁷ , ⁸ But some authors also put forward a kind of mystic regeneration that reminds Libavius' hopes, especially Denis who referred to some vital heat supposed to extend life. ⁷ Moreover, as noted by Raphaële Andrault, ⁵ blood transfusion was also probably connected in the contemporaries' minds with the theory of animal spirits, popularized by Francis Bacon and René Descartes. Denis himself mentioned in his letter to Montmor ⁷ these little subtle corpuscles, supposed to be carried by the blood, thought in the 17th century to be a link between mind and body, and to rule over vegetative functions and movements. ⁹ Finally blood transfusion was quickly forbidden due to accidents, in particular the death of a man who had received a calf's blood transfusion from Denis.

FIGURE 1.

Lamb's blood transfusion in Germany in the 17th century, picture from Purmann MG. Grosser und ganz neugewundener Lorbeer‐Krantz oder Wund‐Artzney. Franckfurth und Leipzig: Michael Rohrlachs; 1692 (biusante.parisdescartes.fr/Bibliothèque interuniversitaire de Santé, Paris/Banque d'images et de portraits).

Almost forgotten in all Europe for more than a century, blood transfusion was revived by Michele Rosa (1731–1812), of Modena, who showed in 1788 in his Lettere fisiologiche that an animal in hemorrhagic shock could be resuscitated by a blood transfusion. His works were corroborated in 1821 by Jean‐Louis Prévost (1790–1850) and Jean‐André Dumas (1800–1884). ¹⁰ The London obstetrician James Blundell (1790–1878) seems to be the first to bring back transfusion in the medical practice in the 1820s. ¹¹ After experiences on dogs, Blundell advocated human blood transfusion, most of the time the husband's, in hopeless cases of delivery hemorrhage. ¹² Of course at a time when blood groups were completely unknown, such blood transfusions led sometimes to disasters as a century before… Very interestingly, despite Rosa's or Prévost and Dumas' works, Blundell seems to have had a vitalist approach of blood transfusion: as shown by Anne‐Marie Moulin, ¹³ he did not think in terms of quantity of blood, but rather in terms of quality: disregarding volumes he did not consider transfusion as the replacement of lost blood, but as the infusion of a vital fluid, which has the power to “turn the wavering balance in our favour.” ¹²

After Blundell's famous works, the practice of blood transfusion spread across Europe, especially from the 1860s, and was used against numerous diseases, including infectious ones. However, two trends took shape and faced each other.

In line with Blundell, encouraged by experiences of researchers like the French physiologist Charles Edouard Brown‐Séquard (1817–1894) (who brought a scientific support to the vitalist approach of blood transfusion in the 1850s), ¹⁴ , ¹⁵ , ¹⁶ , ¹⁷ some doctors tried to use the so‐called vital energy of blood against disorders as varied as cachexia, anemia or infectious diseases: many experiments of transfusion against tuberculosis, but also diphtheria or cholera, were led in the 1870–1880s. ¹⁸ , ¹⁹ , ²⁰ , ²¹ The German Oscar Hasse (1837–1898) is one of the most famous of these transfusion enthusiasts. In the 1870s his works on lamb or human transfusion, especially against tuberculosis, brought him a great reputation. ²² , ²³ As far as we know, none of these experiments of blood transfusion against infectious diseases was underpinned by a scientific reasoning. But the words often betray a vitalist conception of the power of blood: for example Hasse who, as Blundell, did not care about volumes, described the blood donors as “a fresh young girl”, or “a strong, blooming girl.” ²³ Later, attacked about the lack of rationality of his experiments, he referred to an improvement of the patient's “nutritional status” by transfusion (the concept of nutritional status is close to our concept of metabolism). ²⁴

By contrast, some “rationalist” doctors disregarded this vitalist approach. Drawing only on supposed physiological properties of blood, they did not dream of a panacea, but looked for specific cures. In 1866, the German researchers Albert Eulenburg (1840–1917) and Leonard Landois (1837–1902), advocated blood transfusion in a few situations only: acute or chronic anemias, dropsies, leukemias, inanition conditions, and acute poisonings (in this last case they recommended a blood substitution, by repetition of bloodlettings and transfusions). ²⁵ A few years later, in 1875, Peter Ludwig Panum (1820–1885), professor of physiology at the University of Copenhagen, strongly disapproved the use of blood transfusion with no rational justification, and put forward one single indication: the lack of functional red blood cells. Moreover, considering the recently discovered role of the microbes in infectious diseases, he dismissed the use of transfusion in this field. ²⁶ Panum's intervention seemed to drastically slow down the irrational use of blood transfusion, which became marginal from 1876. ²⁷

3. EVOLUTION OF THE IDEAS OF IMMUNITY AND IMMUNIZATION

While the formal concept of immunity against diseases is rather recent (the word immunity is used for the first time in the medical field in the 17th century), ¹³ the idea has long been present in people's minds, as evidenced by early immunization practices. Noticing that healing from some diseases could provide immunity against them, doctors tried to induce mild forms to protect people from serious ones. A lot of countries seem to have experienced immunization techniques, more or less effective, against cutaneous leishmaniasis, measles… and above all against a dreadful and very old illness (death of Pharaoh Ramses V in 1157 BC being the first documented case): smallpox. While some historians believe that Chinese healers performed variolation as soon as in the 10th or 11th century, ²⁸ at least there is evidence of this practice in China in the last 16th century (by skin contact with an infectious patient's clothes, or by nasal spray of smallpox pustules scabs). ²⁹

In Europe variolation spread in the 18th century only, using the method of subcutaneous inoculation of smallpox pus developed by Ottoman doctors. This method, rather risky (a serious case of smallpox happened in one out of 200 variolations), ²⁹ was later replaced by vaccination, after the English doctor Edward Jenner (1749–1823) took advantage of a popular knowledge: bovine mastitis called cowpox (due to vaccinia virus) induces protection against smallpox. In 1798 Jenner disclosed the results of his experiments, and vaccination, that is, inoculation of cowpox pus, became widespread. Figure 2 Other immunization techniques, using variolation‐like methods (inoculation of infectious material), were then developed in the field of veterinary medicine throughout the 19th century, against sheep pox or contagious bovine pleuropneumonia.

FIGURE 2.

Vaccination scene at the time of Jenner, picture from Paris médical, la semaine du clinicien, 1923 (biusante.parisdescartes.fr /Bibliothèque interuniversitaire de Santé, Paris/Banque d'images et de portraits).

However, all these forerunners, unaware of microbiology, weren't able to understand precisely what they did. They only tried to imitate nature with no real theory underlying their works: immunization was widely empirical. Subsequently the concept of immunity remained very vague and more philosophical than scientific. In the 19th century two approaches of immunity faced each other. In line with the current hygienist movement, some limited themselves to describing the various conditions linked with immunity. They merely regarded it as a special status, without going deeper. On the contrary, others stated that immunity was a “resistance force” and took the concept over to support the vitalist theories. ³⁰

Microbiological revolution which happened from the 1860s, and especially in the 1870s under the leadership of the German doctor Robert Koch (1843–1910) and the French chemist Louis Pasteur (1822–1895), was a turning point. As underlined by Anne‐Marie Moulin, the status of immunity switched from an unspecified force to a specific physiological property. ¹³ Researchers gradually understood the role of microbes in pathogenesis, and they could implement scientific experiments but also imagine theories about immunity: immunization became scientific, and immunology arose.

Before describing the progress of immunology during the last quarter of the 19th century, let's underline that we need to get rid of our current vision of immunity. Paul Ehrlich (1854–1915) formulated his side‐chain theory of antibodies only in 1897, so that all the researchers we'll talk about had no idea about the antigen–antibody interaction. On another note, there was no real classification of immunity at that time. People spoke of innate and acquired immunity, but this distinction had nothing to do with the current one. It did not refer to physiological properties (which were unknown), but only to observation: some subjects or species which were naturally resistant to a microbe were told to bear an “innate” or “natural” immunity against it, while the concept of acquired immunity accounted for the resistance after an infection or a vaccination.

Maurice Raynaud (1834–1881), a French doctor (who otherwise described Raynaud's disease), seems to be the first to imagine a link between blood and immunity. He was also probably the first to address the concept of immunity from the point of view of a physiologist, focusing on the role of the host in the host‐pathogen interaction. ³¹ As soon as 1877, he studied the evolution of the vaccinia virus throughout the body during the Jennerian vaccination, wondering how a local and transient phenomenon (the vaccinia pustule) could lead to the general immunity of the body. Raynaud first imagined that the blood carried the vaccinia virus to the whole body, so that the blood of vaccinated subjects should transmit the virus, but his experiences of inoculation of vaccinated children's blood to other children failed. Supposing that the amounts of blood needed to be greater, he then tried real transfusions between animals (cows or horses) and remained confused by the results he got: transfusion of blood from recently vaccinated animals to other animals did not seem to transmit the vaccinia virus (there was no pustule), but immunity itself instead (a later inoculation of vaccine did not induce a pustule)… Raynaud, who obviously thought that immunity was due to the long‐lasting presence of the vaccinia virus throughout the body, called this strange phenomenon “virtual vaccination” (he meant vaccination without vaccine) but, as his following experiments contradicted these first observations, he did not go further. His mind, above all, was probably not ready to dissociate the immunity from the vaccinal particle (i.e., the antigen); that is why he missed humoral immunity and did not realize how original was that so‐called virtual vaccination… not so far, after all, from serum therapy. After lots of experiments Raynaud eventually concluded that the lymphatic system was responsible for the induction of immunity from the vaccinia pustule: in a kind of anticipation of cell‐mediated mechanisms of specific immunity, he wrote that the vaccinia virus was converted inside the lymph nodes into an “elaborated lymph” which was then transmitted through blood to the whole body, conferring immunity. Raynaud however did not try any transfer of this so‐called elaborated lymph. ³² , ³³ , ³⁴

Louis Pasteur was the first to establish scientific procedures for universal immunization. In 1879 he discovered a way to immunize poultry from fowl cholera, with air‐attenuated strains of Pasteurella multocida, ³⁵ and he immediately talked about its generalization against all infectious diseases. During the following years Pasteur and his associates found vaccines (named this way to pay tribute to Jenner) ³⁶ against anthrax (1881), ³⁷ , ³⁸ , ³⁹ swine erysipelas (1883), ⁴⁰ and rabies (1885). ⁴¹ In Pasteur's mind, at least at the beginning (he later changed his mind), vaccines need to be alive. His interpretation of immunity, indeed, was way different from Raynaud's. Familiar with Petri dishes he thought that immunity against a microbe was due to the absence of nutritive elements in the body, either congenitally (innate immunity) or by exhaustion after an infection or a vaccination (acquired immunity). ⁴² Pasteur's belief in this famous assumption, known as “exhaustion theory” (“théorie de l'épuisement”), needs nevertheless to be qualified. He knew that his attenuated bacteria, which did not induce sickness in living organisms, grew in contrast very well in culture media; and he often noticed some local inflammatory reactions after vaccination. Consequently, he wasn't so much convinced, as he confessed in a letter read at the Académie des Sciences in 1880 ⁴³ and, quite funnily for a such great scientist, he sometimes did not hesitate to refer to some vitalist concepts such as “vital resistance” or “natura medicatrix”! ³⁶ , ⁴⁴

In front of Pasteur's exhaustion theory stood the ancestor of the humoral theory of immunity: the “antidote theory” (“théorie du contre‐poison”), formulated by the French vet Auguste Chauveau (1827–1917). Thanks to his experiments with anthrax and sheep Chauveau concluded that immunity was related to some “soluble substances” in the blood, which were hostile to microbes. ⁴⁵ , ⁴⁶ , ⁴⁷ Comparing infection to alcoholic fermentation he thought that these substances were produced by the microbes, not by the host: during the infection they would accumulate in the body and would prevent any new infection once healed. ⁴⁸ , ⁴⁹ As Pasteur's, Chauveau's immunity is therefore passive but, conversely, it is able to be transferred between two individuals. As soon as 1880 Chauveau's disciple Henry Toussaint (1847–1890) tried to transfer the soluble substances supposed to be produced by Bacillus anthracis to immunize against anthrax. He took blood from sick dogs, sheep or ducks, eliminated microbes by filtration, heat exposure or phenol treatment, then inoculated that blood to dogs and sheep. ⁵⁰ , ⁵¹ Later Chauveau himself tried to immunize sheep against anthrax by transfusion of heated sick blood (in order to kill all the microbes). ⁴⁸ Chauveau failed, while Toussaint realized that his methods did not kill the microbes but only attenuated them, what made his immunizations not so different from Pasteur's, so that the two researchers gave up. Nevertheless, although being wrong about humoral immunity, Chauveau and Toussaint's transfusions were genuine transfers of humoral substances responsible for immunity: unlike Raynaud they were fully aware of the presence of particles separate from the microbe.

These works were taken over by other researchers, in order to improve the vaccination procedures: inspired by the antidote theory, they tried to induce immunity with the soluble substances supposed to be produced by the microbes. Unlike Chauveau, they did not use the blood of infected subjects but laboratory cultures previously treated by heat and/or filtration, and showed that immunity could be brought by injection of these altered cultures: let's mention Albert Charrin (1856–1907) with Pseudomonas aeruginosa in 1887, ⁵² Pasteur's associates Emile Roux (1853–1933) and Charles Chamberland (1851–1908) with Clostridium septicum in 1887 ⁵³ then anthrax in 1888, ⁵⁴ André Chantemesse (1851–1919) and Fernand Widal (1862–1929) with typhoid fever in 1888. ⁵⁵ In front of the successes of these new techniques of vaccination, including in his own lab, Pasteur himself changed his mind and came round to the antidote theory. ⁵⁶ , ⁵⁷ Thanks to Chauveau's wrong theory of immunity, vaccination without alive microbes was therefore discovered. Quite ironically the antidote theory did not lead to the discovery of antibodies and humoral immunity, but to the concept of immunizing fraction separate from the microbe, even if nobody then understood how it worked (in their minds immunity was due to the impregnation of the organism with microbe‐made soluble substances).

The real starting point for the understanding of humoral immunity seems to be a work of the Hungarian researcher Josef von Fodor (1843–1901), who showed in 1886 that animals' blood was able to kill nonpathogenic microbes. Fodor also assumed that it was the same with pathogenic ones, ⁵⁸ what was demonstrated 2 years later by an American pupil of the German bacteriologist Carl Flügge (1847–1923), George Nuttall (1862–1937). ⁵⁹ In the same year the German doctor Emil von Behring (1854–1917) showed in experiences with anthrax that this bactericidal action of the blood was due to the blood serum. ⁶⁰ Initially seen as a simple passive chemical property, like for disinfectants, this blood action was quickly shown to be dynamic instead. Very surprisingly the first to assume that the bactericidal property of the blood was a dynamic one, linked with a change in the blood composition, is the father of the cellular theory of immunity: the Russian zoologist Elie Metchnikoff (1845–1916). As soon as 1887 he described that Bacillus anthracis virulence was drastically reduced in the blood of vaccinated sheep. Metchnikoff did not refer to the German concept of blood bactericidy, calling this property “mitigative ability” of the blood (“faculté atténuatrice”), and he attributed it to the action of leukocytes; nonetheless he appears to be the first to put forward a link between vaccination and antibacterial action of the blood. ⁶¹ In October 1888 the Russian Nikola Gamaleïa (1859–1949) went deeper. He carried out some elegant experiments of culture of Bacillus anthracis germs inside the aqueous humor of sheep (i.e., a cell‐free liquid). He noted that the cultures were disturbed in the humor of previously vaccinated sheep (regressive or dissolved forms were observed, and the planting of this humor in agar remained sterile), whereas they were proceeding normally in the humor of non‐vaccinated sheep. Moreover, as it disappeared 1 month after vaccination, such modification seemed transient. Although admitting he was ignoring the nature of the “antiseptic” created by vaccination, Gamaleïa concluded that vaccination generates a “chemical modification” in the liquids of the body, which is harmful to microbes. ⁶² Odessa's bacteriologist therefore synthesized the German school's works (cell‐free blood serum has a bactericidal action) and Metchnikoff's feeling (bactericidy is a dynamic property, which ensues from immunization): Gamaleïa's article “Etude sur la vaccination charbonneuse,” published in the Annales de l'Institut Pasteur in October 1888, can be considered as the founder of the humoral theory of immunity.

4. CHARLES RICHET AND JULES HÉRICOURT'S “HÉMATOTHÉRAPIE”

As a result, everything seems ready in 1888 for the discovery of serum therapy. Interestingly enough they were not the Institut Pasteur bacteriologists who resumed the immunity transfers experiments stopped a few years earlier, but two physiologists of the Faculty of Medicine of Paris, Charles Richet (1850–1935) and his childhood friend Jules Héricourt (1850–1938): Figure 3 that is an illustration of the role of the French school of physiology in formulating the early concepts of immunity. ³¹ , ⁶³ Heir of the great physiologist Claude Bernard (1813–1878), his father's friend, Richet was a genuine product of the French school of physiology, ⁶⁴ , ⁶⁵ while Héricourt was a former medical officer in the French Army, and an experienced bacteriologist. ⁶⁶ The first experiments about immunity that they carried out were, according to Richet's writings, inspired by Chauveau's observations about Algerian sheep which were told to be (naturally) resistant to anthrax. While Chauveau never explained this natural immunity (the antidote theory only accounted for acquired immunity), Richet postulated it was contained in the blood. ⁶⁷ Subsequently they had the idea to try a transfer of this alleged blood‐borne natural immunity (as we told before, the concept of innate immunity at this time had nothing to do with some physiological properties but was only based on observation: the idea of transferring a natural immunity was therefore not as weird as it seems to us). Considering that dogs were naturally resistant to Staphylococcus pyosepticus (a bacterium they had isolated, probably a strain of S. aureus), Richet and Héricourt transfused rabbits with dogs' blood, then they inoculated them with S. pyosepticus 36 hours later. They noted that some rabbits died from this inoculation, while some did not; then they realized that the blood received by surviving rabbits was special: it came from dogs which had been themselves inoculated (by chance) with S. pyosepticus a few months earlier. They concluded that “the blood of dogs which have been previously inoculated by S. pyosepticus, and which have then absolutely recovered, gives a greater immunity than the blood of intact dogs” and they did not hesitate to generalize their discovery: “this influence of dog's blood […] maybe applies to other microorganisms (anthrax, tuberculosis)”. ⁶⁸ Richet and Héricourt's results met those of Metchnikoff and Gamaleïa but they did not mention them, neither they evoked the German concept of bactericidy.

FIGURE 3.

Charles Richet (1850–1935) (left) and Jules Héricourt (1850–1938) (right) (Fonds Watier, Rabelais Fundation; University Library of Medicine, Université François‐Rabelais de Tours).

Shortly after they tried to put their method into practice against tuberculosis, a disease which was then a huge problem of public health. It was a very bad choice, seeing that immunity against tuberculosis is cell‐mediated and not antibody‐mediated, but of course nobody knew it. They first tried to transfer innate immunity by blood transfusion from dogs (told to be resistant to tuberculosis) to rabbits, and they got the impression that such transfusion slowed down the disease progression. ⁶⁹ , ⁷⁰ , ⁷¹ , ⁷² , ⁷³ Then, in November 1890, they tried to perform transfers of acquired immunity by transfusing rabbits with the blood of a dog inoculated with Koch's bacillus a few days before (in order to “strengthen” its resistance against tuberculosis). Although there were few subjects in this experience (3 cases and 3 controls) Richet and Héricourt concluded that their experience was positive. ⁷⁴ Later, in a book published in 1890, they put forward two hypothesis: one hypothesis related to Metchnikoff's phagocytosis theory (“the reaction provoked by the blood […] changes the rabbit's tissues, the phagocytes and the other active elements, so that the animal's resistance to infectious microbes is strengthened by this first struggle against foreign blood”), and one hypothesis, based on humoral theories (“dog's blood contains some substances which penetrate the rabbit's tissues, and which by their own chemical action oppose to the development of the microorganism”). This last hypothesis was their favorite, “starting point of [their] researches”. ⁷⁵

As can be seen, like Chauveau and Toussaint, Richet and Héricourt tried transfers of humoral substances responsible for immunity (innate or acquired), but with a significant difference: while Chauveau and Toussaint used the blood of sick animals, they used a completely microbe‐free blood, either from the outset (blood of naturally resistant animals) or since a long time (blood of healed animals). As there is no dead or alive microbe, there is no possible involvement of the antigen concept in Richet and Héricourt's transfusions: it is a conceptual breakthrough with vaccination.

Further research in that field was carried out in France, but also in Japan. In December 1889 the Japanese Ogata and his student Jasuhara tried some transfers of innate immunity against anthrax. In an article published in the Journal of the Tokyo medical society, they claimed that injections of blood or blood serum from animals told to be resistant to anthrax (frogs, dogs, white rats) could immunize susceptible animals. ⁷⁶ , ⁷⁷ In June 1890 Charles Bouchard (1837–1915) and his disciple Albert Charrin undertook similar experiments with innate immunity and Pseudomonas aeruginosa: according to them the transfusion of dog's blood to rabbits strengthened their resistance to this bacterium. ⁷⁸ A few months later, Georges Bertin (1833–1916) and Jules Picq, from Nantes, who claimed they had never heard about Richet and Héricourt's works, ⁷⁹ performed transfusions to rabbits previously inoculated with Koch's bacillus, using goats' blood, supposed to bear a natural immunity against tuberculosis. ⁸⁰ , ⁸¹ Soon after, they were the first to apply this method to human beings: on the 3rd of December 1890, Bertin and Picq made a subcutaneous injection of goat's blood to a tuberculous man. ⁸² This event seems to have caused a sensation worldwide, as witnessed by a New York Times article in January 1891. ⁸³ Bertin and Picq named hematotherapy (“hématothérapie”) this method of transfer of immunity through blood transfusion, a word which was then widely used in France. ⁸⁴

5. EMIL VON BEHRING'S “BLUTSERUMTHERAPIE”

While the French researchers kept working on hématothérapie, great progress was made in the field of humoral immunity, eventually leading to the development of a new immunity transfer method: Emil von Behring's “Blutserumtherapie”. Figure 4.

FIGURE 4.

Emil von Behring (1854–1917) (biusante.parisdescartes.fr /Bibliothèque interuniversitaire de Santé, Paris/Banque d'images et de portraits).

In 1889 the German researchers Hans Buchner (1850–1902) and Franz Nissen (1862–1928) corroborated Behring's observation: blood serum has bactericidal properties. ⁸⁵ , ⁸⁶ From 1889, the French Albert Charrin and Georges‐Henri Roger (1860–1946) deepened Gamaleïa's works. They studied how pathogenic bacteria behaved in different types of serum (serum from normal, sick or vaccinated animals), and showed that the serum bactericidal power was stronger in sick or vaccinated animals. ⁸⁷ , ⁸⁸ , ⁸⁹ , ⁹⁰ The following year, in 1890, the English bacteriologist Ernest Hankin (1865–1939) showed that the lymph‐cells‐made “globulins” described by William Halliburton (1860–1931) in 1888, ⁹¹ had a bactericidal power similar to that of the serum. He concluded that these globulins were probably responsible for the bactericidal properties of the serum. ⁹² , ⁹³ Then Behring and Nissen showed that the bactericidal properties of a serum against a given microbe did not necessarily work against another one: the serum bactericidal power therefore appears to be specific. ⁹⁴

Emil von Behring also kept working on disinfection, a field he had built his reputation on while being a medical officer in the German Army. ⁹⁵ With his assistant, the Japanese bacteriologist Shibasaburo Kitasato (1852–1931), he studied how to cure the infectious diseases, especially diphtheria, with many disinfectants, as oxygenated water, naphthylamine, metal salts, iodine trichloride, etc., including by internal administration. In particular, he witnessed iodine trichloride effectiveness on diphtheria, and in 1890, a year after the discovery of the diphtheria toxin by Emile Roux and Alexandre Yersin (1863–1943), ⁹⁶ he got a brilliant intuition: “I think it is likely that its therapeutic efficiency [Behring is talking about iodine trichloride] is due not only to its bactericidal effect but also to its toxin‐destroying effect”. Quickly Behring made the connection with immunity, a field he knew quite well, as we told before: “I wondered whether […] immunity is based on the ability of the organism, not to damage the living bacteria, but rather to paralyze their poisonous effect; whether, furthermore, if this is the case, this ability has to be sought in the blood”. ⁹⁷

In December 1890, in two famous articles of the Deutsche medizinische Wochenschrift, he recounted the experiments he carried out with Kitasato, first involving Clostridium tetani (a bacterium discovered in 1887 by Kitasato himself, and whose toxin had just been isolated by the Danish Knud Faber), then Corynebacterium diphtheriae. After having transfused mice with the blood of a tetanus‐vaccinated rabbit, the two researchers inoculated them with Clostridium tetani: they remained in good health whereas control mice died. The same experience with serum instead of blood gave the same results. Then they demonstrated, inverting the sequence transfusion‐inoculation, that such serum also bears curative properties. Eventually they showed that the serum efficacy was due to its ability to destroy the tetanus toxin: they mixed serum from tetanus‐immunized rabbits with massive quantities of toxin and waited for 24 h. Then they injected mice with this mixture: they remained healthy. The authors concluded that the blood serum of tetanus‐immunized rabbits bore destructive properties against the tetanus toxin, so that blood or serum transfusion could give excellent therapeutic effects. ¹ In a second article published the following week, Behring pointed out that these conclusions also apply to diphtheria, and emphasized the curative effect of the method he had described with Kitasato. ⁹⁸ These two articles of the Deutsche medizinische Wochenschrift were the starting point for the development of serum therapy. During the following years Behring's method was developed, both in Germany and France. Although there was some kind of rivalry between these two nations, especially concerning the theories of immunity, ⁹⁹ there was a genuine cooperation between scientists of both countries, as showed by Gabriel Gachelin, ¹⁰⁰ so that progress in the field of serum therapy was quite parallel on either side of the Rhine. ¹⁰¹

The first patient cured by serum therapy is said to be a dying diphtheria child, who received a serum injection from Behring himself, during the 1891 Christmas night in a Berlin hospital. Soon after, assisted by his friend Erich Wernicke (1859–1928), Behring improved his serum ¹⁰² then stated the principles of serum therapy in a book entitled Die Blutserumtherapie. ¹⁰³ In 1894 great therapeutic trials were run with serum from vaccinated horses (which had turned out to be the best animal to provide serum), both in Germany around Behring, and in France around Emile Roux and the Institut Pasteur. Success was huge: for example, in a famous trial carried out in Paris with diphtheria children, including the sickest ones, death rate was divided by more than two (a mortality of 24.5% was observed in the Enfants‐Malades Hospital where the trial took place, whereas during the same timeframe 60% of the diphtheria children died in Trousseau Hospital). ¹⁰⁴ The results of German and French trials were featured at the Budapest 8th International congress for Hygiene and Demography in September 1894, what generated a great enthusiasm worldwide and triggered the industrial production of anti‐diphtheria serum. ¹⁰⁵

The development of serum therapy was a real therapeutic revolution. Of course, medicine was turned upside down by the diphtheria serum, which drastically dropped this disease mortality in a few years. Figure 5 Later, tetanus antitoxin saved many people's lives in the first World War trenches. But success against diphtheria also encouraged more and more researchers to undertake the development of serum therapies against various diseases. Serums were tried against anthrax, rabies, pneumonia, cholera, plague, typhoid fever… It seems that some serums enjoyed real therapeutic successes, although it is impossible for us to know the truth due to the absence of randomized controlled trials. ¹⁰⁶ In a kind of anticipation of our current immunotherapies, serum therapy was even tried against cancer, suspected to be an infectious disease. ¹⁰⁷ The first man who got the idea of an anticancer serum seems to be the founder of the New York Pasteur Institute, a Pasteur's pupil named Paul Gibier (1851–1900), as evidenced by a sealed envelope he sent to the French Académie des sciences as soon as November 1893. However, given that Gibier's letter was opened only in 1895, ¹⁰⁸ Richet and Héricourt were the first researchers to publish in that field. In 1895, after their failure in the development of tuberculosis serum therapy, they began to carry out experiments about anticancer serum therapy, ⁶⁴ , ¹⁰⁹ and they got a few apparent successes ¹¹⁰ , ¹¹¹ which triggered enthusiasm in France, ⁶⁶ and prompted many scientists to investigate the field. ¹¹² However it quickly became clear that such serum only slowed down the disease progression without curing it, and anticancer serum was abandoned.

FIGURE 5.

Emile Roux, as a new St. Michael, saving a child from diphtheria. Allegory published in the Journal illustré, Paris, 28th July 1895 (Fonds Watier, Rabelais Fundation; University Library of Medicine, Université François‐Rabelais de Tours).

Many serums suffered the same fate throughout the 20th century: thanks to the development of more and more vaccinations and, above all, the discovery of antibiotics, the use of serum therapy was gradually restricted.

6. DISCUSSION

Behring's outstanding works, which earned him the first Nobel Prize for Medicine in 1901, triggered the development of serum therapy. However, as can be seen, Richet and Héricourt's hématothérapie seems to be very close to Behring's Blutserumtherapie. The principle of serum therapy thereby appears to be born almost at the same time in two different places, coming from two different intellectual paths.

When examining Richet and Héricourt's first experiences of transfusion, we can't help thinking that they resemble those of Oscar Hasse 15 years earlier. What was their starting intuition when they tried to transfer an alleged natural resistance? Were they influenced by vitalist thoughts? According to later writings, ⁷⁵ they thought about two hypotheses: one based on the first works about humoral immunity (there are chemical substances in the blood), and one related to Metchnikoff's works on phagocytosis (the transfused blood induces a reaction on the receiver's phagocytes and tissues, which strengthens the resistance of the body). This second hypothesis, although of minor interest for them, bears a vitalist overtone. French hématothérapie therefore appears to lie, at least to some extent, in a kind of vitalist tradition which stretches back over centuries.

Emil von Behring, although too severe, did pick this filiation link out in the second volume of his book Die Blutserumtherapie. He implicitly connected the French hématothérapie to the then famous Hasse's transfusions (speaking of “Ernährungs‐Heilmethode”, i.e., a nutritional cure), and reduced it to some considerations of natural philosophy (“naturphilosophischen Erwägungen”) in line with ancient myths like Medea's (on this point Behring was wrong, seeing that Medea, in Ovid's Metamorphoses, doesn't perform a blood transfusion, but only replaces Aeson's “old blood” by a “philter” she made with various ingredients). The way Behring considered hématothérapie is rather exaggerated, of course (Richet and Héricourt draw above all on humoral theories), but it is a fact that he reached the discovery of serum therapy with a totally different turn of mind. As underlined by Jonathan Simon, Behring had a chemical view of immunity, and conceived his works in this field in terms of disinfection ⁹⁵ : distant heir of the 17th century iatrochemists, he lies in the tradition of mechanism. While Behring reasoned as a chemist, considering the chemical changes in the body due to the microbe, Richet and Héricourt reasoned as physiologists focusing on the host's role in immunity. ³¹ The principle of serum therapy therefore appears to originate, almost at the same time, from two schools of thought, with Richet and Héricourt's hématothérapie on one side, and Behring's Blutserumtherapie on the other, reviving the age‐old opposition between vitalism and mechanism.

However, before the birth of hématothérapie and Blutserumtherapie, researchers as Raynaud, Toussaint and Chauveau, did carry out experiences which really looked like serum therapy … Of course they did not formulate the principle of serum therapy, as such principle can emerge only after people conceive the existence of a dynamic (i.e., created by the host) humoral immunity. Before the turning point of Gamaleïa's discoveries in 1888, by lack of any consistent theory, Raynaud, Toussaint and Chauveau could only refer to what we could call induction of immunity: although trying to induce immunity by blood transfusion, they weren't able to imagine doing anything different from Pasteur. Raynaud's transfusions aimed at transferring the vaccine virus (i.e., what we would call the antigen), not immunity itself. Chauveau and Toussaint believed that a transfer of the so‐called “soluble substances” responsible for immunity triggered the same mechanisms as vaccination (an interesting fact: Toussaint precisely called his experiences “vaccinations…”). The discovery of a dynamic humoral immunity allowed the vague concept of induction of immunity to split in two more precise concepts: creation (vaccination) and transfer of immunity (serum therapy). As well as Pasteur's vaccination distinguished itself from ancient immunizations when, at the birth of microbiology, the idea of antigen arose (although not called this way, but rather “vaccine‐virus”, “immunizing fraction” or “vaccinal particle”: i.e., something that induces immunity), serum therapy distinguished itself from vaccination when the idea of a dynamic humoral immunity arose (not yet the idea of antibody, but not so far). Experiences of Richet and Héricourt, Ogata and Jasuhara, Bouchard and Charrin, Bertin and Picq and, of course Behring and Kitasato, marked a break with vaccination, aiming at transferring an already made immunity, instead of creating it. Nevertheless, Raynaud, Toussaint and Chauveau, had the premonition of the blood role in immunity, as soon as in the very beginning of the microbiological revolution triggered by Koch and Pasteur (Raynaud's experiences occurred as soon as 1877, 2 years before Pasteur's first vaccine, while Toussaint performed his blood transfusions in 1880): if they did not invent serum therapy, by lack of an appropriate theoretical background, they were still great forerunners.

Finally, other forerunners must not be forgotten. As we told before, until the late 19th century, blood transfusion had long been fantasized as a transfer of a mysterious vital energy, while immunity, due to the ignorance of its mechanisms, remained a very vague concept until the microbiological revolution, some scientists considering it as a vital resistance. The same concept was therefore invoked for both immunity and blood transfusion… In front of such a syllogism it may be tempting to conclude that, during these confusing times, blood transfusion could be compared to a transfer of immunity. Although a bit far‐fetched, a remote connection can't be denied, and from that perspective serum therapy could be considered as an heir of the transfusions of Hasse, Blundell, Denis, but also of the philosophical considerations of Bacon and Descartes (whose “animal spirits,” by the way, could prefigure the antibodies), the dreams of Libavius and even—why not?—the legendary cure of Asclepius himself. More broadly, the mystical connotation borne by blood in the occidental culture probably played a significant role, influencing doctors over the centuries… including Behring himself, who concluded his Deutsche medizinische Wochenschrift seminal article of December 1890 by this Mephistopheles' mysterious answer to Faust: “blood is a very special juice” (“Blut ist ein ganz besonderer Saft”). ¹

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

Lahaie Y‐M, Watier H. From the Gorgon's blood to Behring's Blutserumtherapie: A long path towards serum therapy. Immunol Rev. 2024;328:13‐23. doi: 10.1111/imr.13391

DATA AVAILABILITY STATEMENT

Data sharing not applicable—no new data generated, or the article describes entirely theoretical research.