Question

lesson 12

1. Where does the activation of activation of complement system? 3. How is the bacterial cell going to be

only need question 2 and 3

Answer 1

When bacteria invade the human body, the innate immune system provides the first line of response, capable of clearing bacteria within minutes to hours upon infection. . The most rapid response is the formation of ring-structured pores the MAC (Membrane attack complex).

Activated complement generates three major types of effectors: anaphylatoxins (C3a and C5a), which are potent pro-inflammatory molecules that attract and activate leukocytes through interaction with their cognate G-protein–coupled receptors.

C3a receptor and C5a receptor which decorate target surfaces through covalent bonding to facilitate transport and favor removal of target cells or immune complexes.

Terminal membrane attack complex (MAC, C5b-9) that directly lyses targeted pathogens.

Activity                                                 Complement molecule

Activation of leucocytes-                Anaphylatoxin receptor on leukocytes C5aR, C3aR

Lysis of bacteria and call-             Membrane attack complex- C5b-9

Oponization-                               C3 and C4

Complement activation results in formation of the membrane attack complex (MAC or C5b-9) that rapidly kills Gram-negative bacteria. Complement labels bacteria with C3-derived products (C3b and C3bi) that stimulate engulfment of bacteria by phagocytes. Release of complement peptide C5a is crucial for attraction of phagocytes to the site of infection.

Killing of bacteria- Activation of C5 results in the release of peptide C5a, a strong chemo attractant that lead to recruit phagocytes towards the site of infection. And concomitant generation of C5b triggers the assembly of the MAC (C5b-9) this kill gram negative bacteria. Complement-dependent bacterial killing is one of the fastest ways to kill an invading bacterium