A diseased patient is exposed to an unknown agent while out of the country. The patient's blood is found to have a high proportion of lymphocytes with CD8 surface proteins in her blood, a likely result of
A) the patient having encountered a bacterial infection which elicited CD8+ T cells.
B) the disease having been caused by a multicellular parasite, such as can be encountered in polluted water sources.
C) the CD8 proteins having been discharged from these lymphocytes to lyse the infected cells.
D) a viral infection eliciting proliferation of CD8+ cytotoxic T cells.
E) the CD8 proteins having "marked" the surface of cells that accumulate after the infection is over and signal patient recovery.

Question

Quizplus · Accepted Answer

CD8 surface proteins are typically found on cytotoxic T cells, which are involved in targeting and destroying infected cells. Viral infections are known to cause the proliferation of CD8+ cytotoxic T cells, making choice D the most likely explanation for their presence in high proportion in the patient's blood. Choices A, B, and E are less likely explanations as they do not specifically involve CD8+ T cells. Choice C is also incorrect as CD8 proteins do not get discharged from lymphocytes to lyse infected cells, but rather act as receptors to recognize infected cells.

A Diseased Patient Is Exposed to an Unknown Agent While