The document summarizes the complement system, its components, activation pathways, and functions. The complement system is a group of plasma proteins that enhance immunity. It consists of 11 main proteins that catalyze enzymatic reactions in three pathways: the classical pathway triggered by antibody-antigen complexes, the alternative pathway activated by bacterial surfaces, and the mannose-binding lectin pathway. The complement system opsonizes pathogens, releases anaphylatoxins, and forms the membrane attack complex to lyse bacteria cells. It also enhances antibody production and inflammation responses.

1. COMPLEMENT SYSTEM
MNEMONICS
Ms. A. INDUMATHI
&
M.V.MALA
PG & RESEARCH DEPARTMENT OF BIOTECHNOLOGY
Bon Secours College for Women, Thanjavur
IMMUNOLOGY

2. ❑ INTRODUCTION
❑ COMPLEMENT COMPONENT
Classical Alternative Mannose Binding Lectin
Pathway Pathway Pathway
❑ BIOLOGIC EFFECTS
❑ REGULATION
❑ CONCLUSION

3. COMPLEMENT COMPONENTS
• Complement was discoverd by Jules Bordet as a heat-
labile component of normal plasma that causes the
Opsonisation and killing of bacteria.
• Group of 20 plasma proteins and essential part in the
innate immunity.
• Word “Complement” enhances or complements our
immunity
• 11 protein are mostly involved name as B, C1-C9 and D.

4. Catalyze a series of enzymatic reactions
Products of complement system
ENZYMES CASCADE the activations of one protein
to another protein with enzyme help
• Attracts macrophagess and neutrophils and also actives
mast cell.

5. Activation of Complement System

6. Classical Pathway
• This pathway involves complement components C1, C2,
C4.
• This pathway is triggered by antibody -antigen complex
binding to C1.
• Three subcomponents C1q, C1r and C1s.
• It produce C3 with help of cnvertase hydeolysis
subcomplement component C3a small and C3b large
fragment.

7. Alternative Pathway
• This pathway involves various factors B,D,H.and I
• This inhibited by molecules on the surface of normal
mammalian cells.
e.g., bacterial lipopolysaccharides (endotoxin), fungal cell
well , and viral envelopes.
• Usually activated by products of micro organisms like
endotoxin.
• One of first responds of innate immune system.

8. Lytic Pathway
• This pathway is initiated by the splitting of C5, and
attachment of C5b to a target.
• C6,C7,C8 and C9 unite with C5b. this membrane attack
complex (MAC).
• C5 C5b C6 MAC
C7
C8 Lysis the bacteria
C9

9. Review

10. Biological Effects
•Opsonization
•Anaphylatoxin
•Cytolysis

11. ➢ OPSONIZATION
• C3b &C1q -enhance phagocytosis

12. ➢ Anaphylatoxin
( C3a,C4a,C5a )
• Smaller complement fragments
➢ Cytolysis (MAC)
• Disrupt the mambrane and entry H2O and electrolyte into
the cell.

13. ➢ Enhancement of antibody production
• Binding of C3b its receptors on the surface of activated
B cells enhanced antibody production.
ROLE OF COMPLEMENT IN DISEASE
▪ This inflammation Response
▪ Fungal infection
▪ Bacterial infection

15. REGULATION
C1 Inhibitor
• Important regulator of classic pathway
Factor H
• Regulate alternative pathway
Properdin
• Protects C3b and stabilizes C3 convertase
Complement receptor
Complement protein

18. CONCLUSION
• The complement system is a group of serum protein,
which participate in innate as well as adaptive immune
response.
• The complement system is characteristically activated by
antigen antibody interaction.
• It is help antibacterial cells and molecules of the immune
system.

19. THANK YOU

20. mnemonic
• CP- 142
• LP- 42
• AP- C3,b,D,B,P
C3
Rest is same