On their own, tumor cells typically do not generate potent antitumor immune responses due to their inefficient expression of molecules that are critical for antigen processing and presentation, such as the antigen transporter gene product TAP-2, MHC class I molecules, and T cell costimulatory molecules such as B7-1 (CD80; Sanda et al., 1995). The gene discussed is CD80; the disease is neoplasm.