HLA-C and neoplasm: Exposure to increasingly acidic pHe has also been shown to reduce tumor cell-induced cytolytic activity of lymphokine-activated killer (LAK) cells [182,183], to play a role in down-regulating cytolytic activity of tumor-infiltrating lymphocytes with natural-killer (NK) phenotype [184] and to inhibit the non-major histocompatibility complex (MHC)-restricted cytotoxicity of immunocompetent effector cells [185-188].