“NK‐like” cytotoxicity of human lymphocytes cultured in media containing fetal bovine serum

Abstract Human peripheral blood lymphocytes (PBL) were found to be highly cytotoxic to a human malignant melanoma target cell line after the PBL were cultured in medium supplemented with 20% fetal bovine serum (FBS). The effector cells had surface markers similar to those of non‐cultured NK effectors against melanoma targets. Both NK (without culture) and the culture‐induced cytotoxic effectors had Fcγ receptors, lacked Fcμ receptors and were either heterogeneous for E receptors or had low‐affinity E receptors. Cells required to generate the FBS response were sensitive to anti‐T serum plus complement, passed through a nylon‐fiber column, formed E rosettes, but lacked detectable receptors for the Fc portions of either IgG or IgM. These results suggest that events causing activation of T cells such as culture of PBL in FBS‐containing medium, result in the augmentation of NK activity.