Question

Which cells constitutively express MHC class I molecules?

• A. Only antigen-presenting cells
• B. Only T lymphocytes
• C. All nucleated cells
• D. Red blood cells

Hint:

Remember: \[ \boxed{ \begin{aligned} \text{MHC Class I} &\rightarrow \text{All nucleated cells} \rightarrow \text{CD8}^{+}\text{ T cells} \text{MHC Class II} &\rightarrow \text{Professional APCs} \rightarrow \text{CD4}^{+}\text{ T cells} \end{aligned} } \]

Answer 1

The Correct Option is C

Step 1: Recall the distribution of MHC Class I molecules. MHC Class I molecules are expressed on \[ \boxed{\text{All nucleated cells}.} \] Their function is to present endogenous peptides to CD8\(^+\) cytotoxic T cells.

Step 2: Eliminate the incorrect options.
• Antigen-presenting cells express both MHC Class I and Class II.
• T lymphocytes are not the only cells expressing MHC Class I.
• Mature red blood cells lack a nucleus and therefore do not express MHC Class I. Hence, \[ \boxed{\text{All nucleated cells}} \] is the correct answer. Therefore, \[ \boxed{(C)} \] is the correct answer.