Mixed lymphocyte culture (MLC) or mixed lymphocyte reaction (MLR) is often used to determine the compatibility of major histocompatibility antigens (HLA antigens) between recipients and donors. MLC is also a commonly used experimental model in immune regulation research because the lymphocytes in MLC are stimulated by alloantigens to activate and proliferate, produce a variety of cytokines, and promote the differentiation of NK, LAK, CTL and other killer cells.