The CD8+ CTLs in TILs can recognize antigen epitopes composed of 8- to 10-aa polypeptides presented by major histocompatibility complex (MHC) class I (human leukocyte antigen [HLA]-A, -B, -C) and kill tumor cells in a specific manner, whereas CD4+ T cells recognize at least 13-aa peptides presented by MHC class II (HLA-DR, -DP, -DQ) molecules. This evidence concerns the gene CD4 and neoplasm.