Which of the following acts as an opsonin?
ANSWER: (B) C3bREF: Robbins 8th ed p. 59See previous question for figure of complement systemsThe following are the basic functions of the complementOpsonization - enhancing phagocytosis of antigensChemotaxis - attracting macrophages and neutrophilsLysis - rupturing membranes of foreign cellsClumping of antigen-bearing agents"The process of coating a particle such as a microbe, to target it for phagocytosis, is called opsonization, and substances that do it are called opsonins"Major opsonins: C3b, IgG, mannose binding lecithin (MBL), fibronectin, fibrinogen and CRP.Membrane attack complex: MAC has a subunit composition of C5b, C6, C7, C8, and polymeric C9Anaphylatoxin: Both C3a and C5a have anaphylatoxin activity
C3a
C3b
C5a
LTB4
Immunology