CD4 and neoplasm: Mutations in the HLA class I or class II molecules could therefore exclude an entire set of neoepitopes that would otherwise be visible to CD8+ T cells, thus facilitating tumour escape.36,37 However, tumour-infiltrating antigen-presenting cells (APCs), professional and non-professional alike, including CD8+ and gamma-delta (γδ) T cells that express HLA-DR38,39 may present tumour-associated antigens to CD4+ TILs in the tumour microenvironment, even when the tumour itself may harbour mutations in the HLA class II pathway.