CD4 and neoplasm: These peptides bind to the major histocompatibility complex (MHC); (2) recruitment of T lymphocytes at the peripheral lymphoid organs and presentation of peptides bound to MHC-I and MHC-II to T cells, with subsequent recognition of peptides bound to MHC-II by receptors on the CD4+ T lymphocytes; (3) training: priming; and activation of effector T cells to respond to the tumor antigens presented; and (4) attack with displacement of activated T cells to the region containing the tumor.