Which statement correctly pairs MHC class I with its T cell partner?

Which statement correctly pairs MHC class I with its T cell partner?

• A. MHC II presents to CD4+ T cells
• B. MHC II presents to CD8+ T cells
• C. MHC I presents to CD4+ T cells
• D. MHC I presents to CD8+ T cells

Answer: (D)

The main idea is how MHC molecules pair with specific T cell subsets. MHC class I sits on almost all nucleated cells and presents peptides generated inside the cell to CD8+ cytotoxic T cells. This allows CD8+ T cells to detect infected or abnormal cells and kill them. In contrast, MHC class II is on professional antigen-presenting cells and presents peptides from outside the cell to CD4+ helper T cells, guiding broader immune responses. Therefore, the correct pairing is MHC class I presenting to CD8+ T cells. The other pairings don’t fit this standard relationship: MHC II pairs with CD4+ T cells, and MHC I does not typically present to CD4+ T cells.

The main idea is how MHC molecules pair with specific T cell subsets. MHC class I sits on almost all nucleated cells and presents peptides generated inside the cell to CD8+ cytotoxic T cells. This allows CD8+ T cells to detect infected or abnormal cells and kill them. In contrast, MHC class II is on professional antigen-presenting cells and presents peptides from outside the cell to CD4+ helper T cells, guiding broader immune responses. Therefore, the correct pairing is MHC class I presenting to CD8+ T cells. The other pairings don’t fit this standard relationship: MHC II pairs with CD4+ T cells, and MHC I does not typically present to CD4+ T cells.