Complement cascade

1. Complement cascade

2. Complement cascade
• Effector in both innate and adaptive immunity
• Complement proteins react sequentially to
cause lysis of bacterial cells or can label
antigen-expressing cells for phagocytosis

3. Complement cascade
• Many complement proteins with enzymatic
activity
• Sequential activation

4. Complement cascade
• Results in
– Cell membrane destruction
– Leakage of contents
– Lysis of bacterial cells
• Complement proteins are found in serum
– C1, C2, C3 & so on

5. Classical complement cascade and cell damage
Cell surface
C4
C2

6. Classical complement cascade and cell damage
Cell surface
C2
C5
C3

7. C2
C5
C3
C6
C8
C9

8. C2
C5
C3
C6
C8
C9
Pore

9. C2
C5
C3
C6
C8
C9
Pore
Attraction of
leukocytes
Phagocytosis &
Anaphylaxis
Membrane
damage & cell
lysis
Attraction of
leukocytes
Phagocytosis &
Anaphylaxis
Membrane
damage & cell
lysis
Attraction of
leukocytes
Phagocytosis &
Anaphylaxis
Membrane
damage & cell
lysis
Attraction of
leukocytes

10. Complement cascade
• Bactericidal and lytic for gram negative
bacteria
• Opsonisation for gram positive bacteria

11. Thank you