1. COMPLEMENT SYSTEM Fe A. Bartolome, MD, FPASMAP Department of Microbiology Our Lady of Fatima University

3. Heat-labile  inactivated by heating serum at 560C for 30 minutes

4. Able to augment the effects of other components of the immune system

7. Activated by Ag-Ab complexes

8. Immunoglobulins involved: IgM and IgG (except IgG4)

9. Involves activation of C1

10. Composed of C1q, C1r, and C1s  binds to Fc portion of IgG and IgM

12. Classic Pathway

13. Classic Pathway

14. Classic Pathway

16. Part of innate immunity

17. Bypasses C1, C4, and C2

18. Does not require an antigen-binding protein

19. Does not wait for antibody to be formed for activation

21. Other activators include:Complexes containing IgA Some virus-infected cells (e.g. EBV) Many gram negative and gram positive organisms Parasites – Trypanosomes, Leishmania Dextran SO4 Erythrocytes Carbohydrates (agarose)

22. Alternative Pathway

23. Alternative Pathway

25. Activated by binding of mannose-binding lectin (or mannose-binding protein) to surface of microbes bearing mannan(polymer of the sugar mannose) in a calcium dependent manner

28. Presence of C3b on surface of a microbe marks it as foreign and targets it for destruction

29. C3b with two important functions:Combines with other complement components to generate C5 convertase Opsonizes bacteria

36. A serine protease inhibitor (serpin)

38. Reduce amount of C5 convertase available

40. Prevents assembly of C3bBb or accelerates disassembly of preformed convertase  no formation of MAC

45. Mutations in factor I gene  implicated in development of Hemolytic Uremic Syndrome