What is displayed in the grooves of MHC antigens?

• A. Antibodies
• B. Peptides
• C. Membrane proteins
• D. Carbohydrates

Answer: (B)

MHC (Major Histocompatibility Complex) molecules play a crucial role in the immune system by presenting antigens to T cells. The grooves of MHC antigens are specifically designed to display peptide fragments derived from proteins that have been processed within the cell. These peptides are typically 8-11 amino acids in length for MHC class I molecules and can be longer for MHC class II molecules, which present to CD4+ T helper cells.

When a cell is infected or otherwise altered, proteins within the cell are broken down into peptides. These peptides are then transported into the endoplasmic reticulum, where they bind to MHC molecules. Once the MHC-peptide complex is formed, it is transported to the cell surface, where it can be recognized by T cells.

This presentation of peptides is essential for the immune response, as it allows T cells to identify infected or abnormal cells. The recognition of these peptide-MHC complexes is critical for the activation of T cells, which can then initiate a variety of immune responses to eliminate the source of infection or dysfunction.