Which cell-surface marker is primarily responsible for presenting endogenous (intracellular) peptide antigens to CD8+ T cells during immune reactions?

• A. CD4
• B. MHC class II
• C. B cell receptor (membrane immunoglobulin)
• D. MHC class I

Answer: (D)

Verified step by step guidance

1. Understand the role of cell-surface markers in antigen presentation, which is crucial for immune system recognition of pathogens or infected cells.
2. Recall that endogenous (intracellular) peptide antigens are typically presented by molecules that display peptides derived from proteins synthesized within the cell.
3. Identify that CD8+ T cells recognize antigens presented by MHC class I molecules, which are found on almost all nucleated cells and present peptides from intracellular proteins.
4. Differentiate MHC class I from MHC class II: MHC class II presents exogenous (extracellular) antigens to CD4+ T cells, while MHC class I presents endogenous antigens to CD8+ T cells.
5. Conclude that the primary cell-surface marker responsible for presenting endogenous peptide antigens to CD8+ T cells is MHC class I.