MHC Class I vs. MHC Class II: Key Differences in Antigen Presentation
MHC Class I displays peptides from inside the cell on every nucleated cell, telling cytotoxic T cells, “I’m healthy or infected.” MHC Class II presents peptides from outside the cell only on professional antigen-presenting cells, alerting helper T cells to invaders. Students and clinicians often conflate the two because both are “MHC,” yet forgetting which…