Question

MHC class II molecules are primarily found on

• A. All nucleated cells
• B. Red blood cells
• C. Antigen presenting cells
• D. Blood platelets

Hint:

MHC I is on all nucleated cells; MHC II is only on professional antigen presenting cells like B cells, dendritic cells, and macrophages.

Answer 1

The Correct Option is C

Step 1: Understand MHC molecules.
Major Histocompatibility Complex (MHC) molecules are essential for the immune system to recognize foreign molecules. There are two classes—MHC I and MHC II. Step 2: Identify where MHC II is found.
MHC class II molecules are present only on the surface of specific immune cells known as Antigen Presenting Cells (APCs), such as dendritic cells, macrophages, and B cells. These molecules present processed antigens to helper T cells (CD4+). Step 3: Evaluate the options.
- All nucleated cells express MHC class I, not class II. - Red blood cells lack nuclei and do not express MHC molecules. - Antigen presenting cells is the correct answer. - Blood platelets do not express MHC class II. Conclusion: MHC class II molecules are found primarily on Antigen presenting cells (Option 3).