Suppression of T cell functions occurs through downregulation of MHC molecules and co-stimulatory ligands, with upregulation of inhibitory receptors like programmed cell death protein ligand 1 (PD-L1) on tumor cells and cytotoxic T-lymphocyte antigen-4 (CTLA-4, CD152) [143]. The gene discussed is CTLA4; the disease is neoplasm.