An Abnormal Cell Would Be Identified by the Immune System

Question

An abnormal cell would be identified by the immune system because it showed
A) Class I MHC proteins.
B) Class II MHC proteins.
C) Class I MHC proteins with an antigen bound.
D) Class II MHC proteins with an antigen bound.
E) a CD3 receptor complex in the membrane.

Accepted Answer

Abnormal cells are often recognized by the immune system through the presentation of abnormal peptides bound to Class I MHC proteins. This signals to the immune system that the cell is abnormal and needs to be targeted for destruction. Choice A is incorrect because normal cells also present Class I MHC proteins. Choice B is incorrect because Class II MHC is primarily used for presenting antigens from extracellular pathogens to helper T cells. Choice D is also incorrect for this reason. Choice E is incorrect because the CD3 receptor complex is found on all T cells and is not specific to abnormal cells.