Question

Class-I MHC molecules are associated with:

• A. Tc-cells and Th-cells
• B. All nucleated cells of the body and Tc cells
• C. All nucleated cells of the body and Th cells
• D. Red blood cells and Tc cells

Hint:

Class I MHC molecules play a critical role in the immune response against intracellular pathogens by presenting antigenic peptides to cytotoxic T cells.

Answer 1

The Correct Option is B

Step 1: MHC molecules (Major Histocompatibility Complex) are cell surface proteins that play a critical role in the immune system by presenting antigenic peptides to T-cells. There are two main classes: Class-I and Class-II MHC molecules. 
Step 2: Class-I MHC molecules are present on all nucleated cells of the body. These molecules present endogenous antigens (such as those from intracellular pathogens) to Tc-cells (cytotoxic T cells). This is essential for the immune system to recognize and destroy infected or abnormal cells.
Step 3: Class-I MHC molecules do not present antigens to Th-cells (helper T cells). Helper T-cells recognize antigens presented by Class-II MHC molecules, which are expressed only on professional antigen-presenting cells (such as dendritic cells, macrophages, and B cells). 
Step 4: Red blood cells (Option 4) do not have nuclei, and therefore they do not express Class-I MHC molecules. 
Conclusion: Class-I MHC molecules are associated with all nucleated cells of the body and Tc cells, making Option (2) the correct answer.