One group of immune deficiency diseases is caused by an inability of CD8 effector T cells to kill virus-infected target cells, due to defects in cytotoxic vesicle exocytosis. Because of the inflammatory response that accompanies a normal virus infection, together with the prolongation of this response due to the inability to control the infection, patients with these disorders suffer from tissue damage caused by the infiltration of effector CD8 cells and activated macrophages into multiple organs. In addition, a subset of these patients also show increased susceptibility to extracellular and intracellular bacterial infections. This is because:
A) CD8 T cells are required to kill extracellular bacteria.
B) CD8 T cells in these patients are defective in producing IFN-$\gamma$.
C) Some proteins required for cytotoxic vesicle exocytosis are required for phagosome-lysosome fusion.
D) Inflammatory cytokines in these patients are inducing macrophages to phagocytose red and white blood cells.
E) Persistent uncontrolled herpesvirus infections cause immunosuppressive effects on bacterial clearance mechanisms.

Question

Quizplus · Accepted Answer

Some proteins required for cytotoxic vesicle exocytosis are also involved in phagosome-lysosome fusion, which is important for the killing of intracellular bacteria. Therefore, defects in cytotoxic vesicle exocytosis can lead to an inability to control both viral and bacterial infections.

One Group of Immune Deficiency Diseases Is Caused by an Inability