However, tumour cells can survive immune destruction and may enter a subsequent phase called ‘Equilibrium’; whereby immunoediting occurs through cell-associated antigen mutation, downregulation, deletion and/or selective survival of certain antigen negative or positive subpopulations, involving downregulation of major histocompatibility complex (MHC)—class II, increased expression of cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programed cell death protein (PD-1), IL-10 and TGF-β, in addition to recruitment of regulatory T cells to dampen the immune response [15, 16]. The gene discussed is CTLA4; the disease is neoplasm.