Question

Which class of MHC molecules is found on the surface of all nucleated cells?

• A. MHC Class I
• B. MHC Class II
• C. MHC Class III
• D. MHC Class IV

Hint:

MHC I → Present on all nucleated cells → Presents intracellular antigens.

Answer 1

The Correct Option is A

Concept: Major Histocompatibility Complex (MHC) molecules are cell surface proteins that play a crucial role in immune response by presenting antigenic peptides to T-cells.
Step 1: Understanding MHC Class I.
MHC Class I molecules are present on the surface of all nucleated cells in the body.
Step 2: Function.
They present endogenous (intracellular) antigens to cytotoxic T-cells (CD8+ T cells).
Step 3: Comparison with other classes.

• MHC Class II: Found only on antigen-presenting cells (macrophages, dendritic cells, B-cells)
• MHC Class III: Involved in complement proteins, not antigen presentation

Step 4: Importance.
This widespread presence allows the immune system to monitor all cells for infection or abnormal changes.
Step 5: Conclusion.
Thus, MHC Class I molecules are found on all nucleated cells.