In this model, CD4+ T cells were critical for rejection of MUC1-positive tumours (Tempero et al, 1998; VanLith et al, 2002), whereas other studies suggest that CD8+ T cells are required for MUC1-specific immunity against MUC1-positive pancreatic carcinoma (Morikane et al, 2001). The gene discussed is CD8A; the disease is exocrine pancreatic carcinoma.