Question

1.1Which of the following are functions of C5a (select all that apply)? a. Inhibit release of cytokines and histamines by localized cells. b. Decrease vasular permeability at site of infection c. Enhance adherence of monocytes and neutrophils to blood vessel walls. d. Promote migration of macrophages and lymphocytes to site of infection e. Stimulate phagocytosis of complemnt bound pathogens

1.2 The C5 convertase cleaves C5 into C5a and C5b which primarily does which of the following (select one)? a. Promote opsonization of pathogen, b. Formation of C3 convertase, c. Formation of Membrane Attack Complex and lysis of microbial cell, d. Recruitment of Mannose Binding Lectin, or e. Recruitment of Ficolin

Answer 1

Answer-

According to the given question-

Question 1.1-

We know that the complement system or cascade, are responsible for enhancing the capability of antibodies as well as several phagocytic cells in clearing the damaged cells and microorganism from the body and also helps in promoting inflammation, and formation of membrane attach complex to destroy pathogen.

C 5 or Complement component 5 is a protein which is part of complement system and are cleaved by C5-convertase into Smaller fragment C5a called anaphylatoxins and C5b which helps in formation of membrane attack complex. C5a helps in chemotactic and spasmogenic activity.

· Responsible for recruitment of several inflammatory cells such as eosinophils, monocytes and neutrophils.

· Activate phagocytic cells

· Causes release of histamine from mast cells.

· Contraction of smooth muscle, vasodilation,

· Increases vascular permeability.

· Responsible for mediating chemotaxis, as well as inflammation

· Release of cytokine and chemokines.

· Increase migration as well as adherence of monocyte and neutrophils to the wall of blood vessels.

· Causes accumulation of phagocytic and complement cells where infection was observed.

So correct answer is (c) , (d) and (e).

Question 1.2-

Small fragments of complement protein C5a work on specific receptors and responsible for producing inflammatory responses and are called anaphylatoxins. C5b helps in formation of membrane-attack complex when cleaved by C5 convertase. C5b attaches to C6, and leads to formation of C5b,6 complex which binds with C7 and this leads to conformational change and also exposure of a hydrophobic site on C7 complex. Now this complex inserts into bilayer of lipid and other site which was hydrophobic sites was exposed to C8 and C9 proteins and induces polymerization of C9 into membrane-attack complex.

So correct answer is (C) Formation of Membrane Attack Complex and lysis of microbial cell.