Question

Class I MHC molecules present peptides to which of the following cell type?

• A. CD8+ cytotoxic T-cells
• B. CD4+ T-helper cells
• C. Dendritic cells
• D. Macrophages

Hint:

Use the "rule of 8" to remember the MHC-T cell interactions:

MHC Class \textbf{I} binds to CD\textbf{8} T-cells (\(1 \times 8 = 8\)).
MHC Class \textbf{II} binds to CD\textbf{4} T-cells (\(2 \times 4 = 8\)). \end{itemize}

Answer 1

The Correct Option is A

Step 1: Concept Overview:
Major Histocompatibility Complex (MHC) molecules are cell-surface proteins displaying antigenic peptides to T-cells. MHC Class I and MHC Class II are the two primary types, presenting peptides to distinct T-cell populations.

Step 2: Detailed Explanation:
- MHC Class I: Found on nearly all nucleated cells, these molecules present {endogenous} antigens (peptides from intracellular proteins like viral or tumor proteins) to CD8+ cytotoxic T-cells. This signals the cytotoxic T-cell to eliminate the compromised cell.
- MHC Class II: Located on professional Antigen-Presenting Cells (APCs) such as dendritic cells, macrophages, and B-cells, these present {exogenous} antigens (peptides from ingested and processed pathogens) to CD4+ T-helper cells, activating them to coordinate a broader immune response.

Step 3: Conclusion:
MHC Class I molecules specifically present peptides to CD8+ cytotoxic T-cells, making option (A) correct.