TABLE 2.

Characteristics of tuberculosis in humans and in laboratory animals^a

Species	TB characteristicf
	Tuberculin-type allergy (DTH)	Caseous necrosis (due to DTH)b	CMI	Cavity formation
Isolated human populationsc	+++++	+++++	++	+++
Rhesus monkeysd	++	+++++	++	+++
Guinea pigs	+++	+++++	++	+
Modern humans
Immunocompetent	+++++	+++++	++++	+++++
Immunosuppressed	+	+++++	+	+
Rabbitse
Resistant	++	+++	++++	++++
Susceptible	++	+++++	++	0
Mice	+	+/−	+++	0

^aReproduced from reference 37 and based on data from a table by Francis (50). References 29 and 100 reproduce the entire Francis table (which contains many other animal species, including elephants).

^bTissue-damaging DTH is the cause of caseous necrosis. Tubercle bacilli are dormant in solid caseum, and many do not survive there. In arrested human and rabbit tuberculous lesions, solid caseum is often encapsulated by fibrous tissue.

^cIsolated human populations refer to those who had been exposed to M. tuberculosis only during the last several centuries, such as the Senegalese troops brought from Africa to Europe during the first World War (14, 28; see reference 98).

^dCynomolgus monkeys are more resistant to tuberculosis than rhesus monkeys and may even arrest the disease (see the text).

^eThe characteristics of tuberculosis in Lurie's inbred resistant and susceptible rabbits are reviewed in references 64 and 66.

^fThe assignment of + to +++++ is an estimate for a given species as a whole. Good CMI and DTH are both needed to arrest the disease. Guinea pigs have good DTH but relatively poor CMI, and mice have good CMI but relatively poor DTH. Both species show progressive disease leading to their death. Most humans and rabbits (infected with virulent human-type tubercle bacilli) have adequate amounts of DTH and CMI to arrest the disease.