Which of the following is an opsonin?

Ans. b. C3bRef: Robbins and Cotran Pathologic Basis of Disease 9th Ed; Page No-132Complement: System of hepatically synthesized plasma proteins that play a role in innate immunity and inflammation. Membrane attack complex (MAC) defends against gram [?] bacteria.Function of the ComplementC3b--opsonization.C3a, C4a, C5a--anaphylaxis.C5a--neutrophil chemotaxis.C5b-9--cytolysis by MACMnemonicC3b binds bacteriaOpsonins--C3b and IgG are the two 1deg opsonins in bacterial defense; enhance phagocytosis. C3b also helps clear immune complexes.Inhibitors--decay-accelerating factor (DAF, also known as CD55) and C1 esterase inhibitor help prevent complement activation on self-cells (e.g. RBCs).