Many tumours produce and accumulate lymphokines or factors at high levels that may inhibit vaccine-induced T-cell responses such as IL-6, transforming growth factor (TGFβ), IL-10, cyclooxygenase (COX)-2, and its product prostaglandine E, PD1-ligand or indolamine, 2,3-dioxygenase (IDO; Gajewski et al, 2006). The gene discussed is IDO1; the disease is neoplasm.