Alloreactive cytotoxicity of interferon-triggered human lymphocytes detected with tumor biopsy targets.

Interferon activation of lymphocytes produces lytic potential against allogeneic but not against autologous biopsy-derived tumor cells. This effect was seen when targets isolated from solid tumors were used directly without cultivation in vitro. The hypothesis that the lytic effect was due to activation of alloreactive cells was tested in the cold target competition assay. The results substantiated our assumption because they showed that in a given lymphocyte population separate sets act on allogeneic tumor cells derived from different individuals. In addition PHA blasts from the target-cell donor but not from unrelated individuals also inhibited the lysis. The system we use is operationally an NK assay in which antigen (MHC)-recognizing lymphocytes seem to function. Since antigen recognition is a property of the T subset, the conceptual dualism in the classification of NK and CTL effects should be modified.