The mechanisms by which TH1 cells protect against microbes include all of the following EXCEPT:
A)Secretion of interferon (IFN)-ƴ,which activates microbicidal functions of macrophages
B)Expression of CD40 ligand, which binds to CD40 on macrophages and activates them
C)Secretion of IFN-ƴ, which promotes B cell production of opsonizing antibodies
D)Secretion of lymphotoxin and tumor necrosis factor, which enhance neutrophil killing of ingested microbes
E)Release of granzyme B, which stimulates apoptosis of bacteria

Question

Quizplus · Accepted Answer

Granzyme B, a product of CD8⁺ cytolytic T lymphocytes, promotes death of infected host cells, but not of extracellular microbes. The principal function of TH1 cells is to enhance phagocyte defense against intracellular infections. Interferon (IFN)-ƴ and CD40 ligand, produced by TH1 cells, enhance killing of microbes ingested by macrophages, in part by stimulating the production of inducible nitric oxide synthase and phagocyte oxidase. IFN-ƴ, produced by TH1 cells, is an isotype switch factor, promoting the production of IgG subtypes that bind to Fc receptors on phagocytes and fix complement. Therefore, these opsonizing IgG subtypes facilitate the phagocytosis of the microbes to which they bind. TH1 cells also secrete tumor necrosis factor and lymphotoxin, two cytokines that can activate neutrophil killing of internalized microbes.

The Mechanisms by Which TH1 Cells Protect Against Microbes Include