A key aspect of tumor immune surveillance is that costimulatory or coinhibitory ligands, such as B7-1 or PD-L1, that interact with cognate costimulatory or coinhibitory receptors, such as CD28/CTLA-4 or PD-1, on T cells to elicit or suppress tumor-antigen-specific immune responses, respectively (25). The gene discussed is CTLA4; the disease is neoplasm.