Although primary CD8+ T-cell responses have been shown to be generated in the absence of CD4+ T cells, CD4+ T cells appear to be required for the generation of effective anti-tumour memory CD8+ T cells in many systems (Belz et al, 2002; Janssen et al, 2003; Shedlock and Shen, 2003; Sun and Bevan, 2003). The gene discussed is CD4; the disease is neoplasm.