Abstract
It has been demonstrated that C1 isolated in the unactivated form fails to inactivate C4 or C2 in the fluid phase, while the activated molecule, C1 rapidly converts C4 to hemolytically inactive C4i, but does not efficiently inactivate C2. The production and presence of C4i now confers on C1 the ability to rapidly inactivate C2. After heating at 56°C, so as to destroy the hemolytic activity, heat inactivated C1 is still capable of inactivating C4 but the presence of C4i no longer confers an ability to inactivate C2. Studies with the subunits of C1–C1q, C1r, C1s, indicate that the action of C1s on C2 can be inhibited by C1r and that this inhibition is reversed by the presence of homologous C4. These studies indicate that the interaction of C4i with a heat labile receptor conformation in C1 uncovers a masked specificity for C2.
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Selected References
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- BORSOS T., RAPP H. J., WALZ U. L. ACTION OF THE FIRST COMPONENT OF COMPLEMENT. ACTIVITATION OF C'1 TO C'1A IN THE HEMOLYTIC SYSTEM. J Immunol. 1964 Jan;92:108–117. [PubMed] [Google Scholar]
- Borsos T., Rapp H. J. Hemolysin titration based on fixation of the activated first component of complement: evidence that one molecule of hemolysin suffices to sensitize an erythrocyte. J Immunol. 1965 Sep;95(3):559–566. [PubMed] [Google Scholar]
- Borsos T., Rapp H. J. Immune hemolysis: a simplified method for the preparation of EAC'4 with guinea pig or with human complement. J Immunol. 1967 Aug;99(2):263–268. [PubMed] [Google Scholar]
- Colten H. R., Borsos T., Rapp H. J. Ultracentrifugation of the first component of complement: effects of ionic strength. J Immunol. 1968 Apr;100(4):808–813. [PubMed] [Google Scholar]
- Gigli I., Austen K. F. Fluid phase destruction of C2hu by C1hu. I. Its enhancement and inhibition by homologous and heterologous C4. J Exp Med. 1969 Apr 1;129(4):679–696. doi: 10.1084/jem.129.4.679. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Gigli I., Ruddy S., Austen K. F. The stoichiometric measurement of the serum inhibition of the first component of complement by the inhibition of immune hemolysis. J Immunol. 1968 Jun;100(6):1154–1164. [PubMed] [Google Scholar]
- Kempf R. A., Gigli I., Austen K. F. Inhibition of the lytic effect of guinea pig complement by rabbit complement. J Immunol. 1969 Apr;102(4):795–803. [PubMed] [Google Scholar]
- Laurell A. B., Siboo R. Activation of C'1 to C'1 esterase on gel filtration on Sephadex G-200. Studies on normal human serum, euglobulin and hereditary angioneurotic edema serum. Acta Pathol Microbiol Scand. 1966;68(2):230–242. doi: 10.1111/apm.1966.68.2.230. [DOI] [PubMed] [Google Scholar]
- MUELLER-EBERHARD H. J., LEPOW I. H. C'1 ESTERASE EFFECT ON ACTIVITY AND PHYSICOCHEMICAL PROPERTIES OF THE FOURTH COMPONENT OF COMPLEMENT. J Exp Med. 1965 May 1;121:819–833. doi: 10.1084/jem.121.5.819. [DOI] [PMC free article] [PubMed] [Google Scholar]
- MULLER-EBERHARD H. J., KUNKEL H. G. Isolation of a thermolabile serum protein which precipitates gamma-globulin aggregates and participates in immune hemolysis. Proc Soc Exp Biol Med. 1961 Feb;106:291–295. doi: 10.3181/00379727-106-26313. [DOI] [PubMed] [Google Scholar]
- NAFF G. B., PENSKY J., LEPOW I. H. THE MACROMOLECULAR NATURE OF THE FIRST COMPONENT OF HUMAN COMPLEMENT. J Exp Med. 1964 Apr 1;119:593–613. doi: 10.1084/jem.119.4.593. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Naff G. B., Ratnoff O. S. The enzymatic nature of C'1r. Conversion of C'1s to C'1 esterase and digestion of amino acid esters by C'1r. J Exp Med. 1968 Oct 1;128(4):571–593. doi: 10.1084/jem.128.4.571. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nagaki K., Stroud R. M. The relationship of the hemolytic activity of active C'1s to its TAMe esterase action: a new method of purification and assay. J Immunol. 1969 Feb;102(2):421–430. [PubMed] [Google Scholar]
- Nelson R. A., Jr, Jensen J., Gigli I., Tamura N. Methods for the separation, purification and measurement of nine components of hemolytic complement in guinea-pig serum. Immunochemistry. 1966 Mar;3(2):111–135. doi: 10.1016/0019-2791(66)90292-8. [DOI] [PubMed] [Google Scholar]
- Polley M. J., Müller-Eberhard H. J. The second component of human complement: its isolation, fragmentation by C'1 esterase, and incorporation into C'3 convertase. J Exp Med. 1968 Sep 1;128(3):533–551. doi: 10.1084/jem.128.3.533. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ruddy S., Austen K. F. A stoichiometric assay for the fourth component of complement in whole human serum using EAC'la-gp and functionally pure human second component. J Immunol. 1967 Dec;99(6):1162–1172. [PubMed] [Google Scholar]