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Number of hits necessary for complement-mediated hemolysis
Insights
Immune hemolysis mechanisms were studied using complement components C8 and C9. Human C9 exhibits a multi-hit response, suggesting a single C8 and multiple C9 form lesions during hemolysis.
Area of Science:
- Immunology
- Complement System
Background:
- Immune hemolysis is a critical process mediated by the complement system.
- Understanding the specific roles of complement components C8 and C9 is crucial for elucidating lysis mechanisms.
Purpose of the Study:
- To reexamine the number of hits required for complement component 8 (C8) and complement component 9 (C9) in immune hemolysis.
- To investigate the mechanism of immune hemolysis using human and guinea pig complement components.
Main Methods:
- An experimental design involving varying numbers of EAC1-7 with excess or constant amounts of complement components.
- Analysis of lysis curves for sensitized erythrocytes (EA) using normal and C9-deficient human serum.
Main Results:
- Guinea pig C8 and C9, and human C8 followed a one-hit mechanism.
- Human C9 demonstrated a multi-hit response.
- Lysis by normal human serum yielded one-hit curves, while C9-deficient serum produced multiple-hit curves.
Conclusions:
- Immune hemolysis in humans involves a single C8 and multiple C9 forming a single lesion.
- Normal human serum has an excess of C9, contributing to the one-hit lysis mechanism.
- The lysis mechanism by C5b-8 may differ from that by C5b-9.
Abstract:
The number of hits necessary for the C8 and C9 steps of immune hemolysis was reexamined with a previously unemployed experimental design, in which various numbers of EAC1-7, excess of the supplementary component and a constant amount of the component tested were incubated in a constant volume (Inoue et al. 1976. Infect. Immun. 13: 337). Our results were consistent with previous findings; the steps of guinea pig C8 and C9, the human C8 each followed a one-hit mechanism, while that of human C9 showed ka multi-hit response. When lysis of sensitized erythrocytes (EA) by normal human serum was analysed in a similar way, one-hit curves were obtained. This result, taken together with the above results, suggests that immune hemolysis occurs by a single lesion including a single C8 and multiple C9 in the case of human complement and that normal human serum contains sufficient excess of C9. On the other hand, when C9-deficient human serum was used for lysis of EA, multiple-hit curves were obtained. The mechanism of lysis by C5b-8 may differ from that by C5b-9.