CD4 and neoplasm: Previously, we have proposed that tumour-specific CD4+ T cells, especially T-helper type 1 (Th1) cells play a critical role for inducing cytotoxic T lymphocytes (CTL)-mediated antitumour immunity in tumour-bearing mice (Nishimura et al, 1999; Ikeda et al, 2004; Chamoto et al, 2006; Zhang et al, 2006).