CD4 and neoplasm: In addition, expressed on professional antigen-processing cells (APCs), such as DCs, macrophages, and B cells, class II MHC molecules (MHC-II) present exogenous peptides to activate CD4 + T cells.88,89 Despite substantial research on MHC-I and tumor immunotherapy, recent studies have shown that tumor-specific MHC-II molecules are also associated with favorable outcomes in patients with cancer.90 MHC IIIs are not markers on the cell surface and are not discussed here.