Question

What is the length of peptides binding to Major Histocompatibility Complex (MHC) class II molecule?

• A. 8-11 amino acids
• B. 21-27 amino acids
• C. 15-20 amino acids
• D. 507 amino acids

Hint:

MHC class II molecules bind peptides that are generally 15-20 amino acids long. These peptides are recognized by helper T-cells and play a key role in adaptive immunity.

Answer 1

The Correct Option is C

Step 1: Understanding MHC class II molecules.
MHC class II molecules are crucial components of the immune system. They present foreign peptides to T-cells, allowing the immune system to recognize and respond to pathogens. These peptides are processed and bound to MHC class II molecules in antigen-presenting cells (APCs) like dendritic cells, macrophages, and B-cells.

Step 2: Peptide length for MHC class II.
Peptides that bind to MHC class II molecules are typically in the range of 15 to 20 amino acids. These peptides are recognized by helper T-cells to initiate an immune response.

Step 3: Discarding other options.

• Option 1 (8-11 amino acids): ❌ This peptide length is typical of peptides that bind to MHC class I molecules, not MHC class II.
• Option 2 (21-27 amino acids): ❌ This peptide length is too long for MHC class II molecules, as they typically bind peptides within the 15-20 amino acid range.
• Option 4 (507 amino acids): ❌ This peptide length is far too large. Peptides presented by MHC molecules are typically in the range of a few dozen amino acids.

Step 4: Conclusion.
Therefore, the correct peptide length for MHC class II molecules is 15-20 amino acids.