What Do NK Cells Use to Distinguish Between Self and Nonself

Question

What do NK cells use to distinguish between self and nonself?
A) platelets
B) MHC class I molecules
C) macrophages
D) dendritic cells
E) monocytes

Accepted Answer

NK cells use MHC class I molecules to distinguish between self and nonself. Normal cells express MHC class I molecules on their surface, which NK cells recognize as "self" and do not attack. However, infected or cancerous cells often downregulate MHC class I expression, which makes them vulnerable to NK cell-mediated recognition and destruction.