Which statement about CD4+ T cell antigen recognition is accurate?

Which statement about CD4+ T cell antigen recognition is accurate?

• A. It requires Class I MHC molecules.
• B. It requires Class I MHC molecules and Class II in combination.
• C. It does not involve MHC molecules.
• D. It requires Class II MHC molecules.

Answer: (D)

CD4+ T cells (helper T cells) recognize peptide antigens only when they are presented by MHC class II molecules on professional antigen-presenting cells. The T cell receptor binds the peptide–MHC II complex, with the CD4 co-receptor stabilizing this interaction and boosting signaling. This pathway is distinct from CD8+ T cells, which recognize peptides on MHC class I molecules. Therefore, the accurate statement is that recognition by CD4+ T cells requires Class II MHC molecules.

CD4+ T cells (helper T cells) recognize peptide antigens only when they are presented by MHC class II molecules on professional antigen-presenting cells. The T cell receptor binds the peptide–MHC II complex, with the CD4 co-receptor stabilizing this interaction and boosting signaling. This pathway is distinct from CD8+ T cells, which recognize peptides on MHC class I molecules. Therefore, the accurate statement is that recognition by CD4+ T cells requires Class II MHC molecules.