Studies on cytotoxicity generated in human mixed lymphocyte cultures

Stimulation of human peripheral blood lymphocytes with allogeneic cells in mixed lymphocyte culture (MLC) results in increased NK-like cytotoxicity against K562 targets. The effector cells of this cytotoxicity were shown to include both Fcμ+ and Fcμ− cells, as shown by EAμ rosette separation and by combined rosette formation and single-cell analysis. Peak cytotoxic activity of Fcμ+ cells was found after 3 days of MLC stimulation. The Cytotoxicity against KS62 targets mediated by Fcμ+ cells could not be inhibited at all with alloantigen-bearing cells and could only be partially inhibited with another NK-sensitive target (MOLT- 4). This cytotoxicity could be generated from either Fcγ+ or FCγ− cells. These results indicate considerable heterogeneity of NK-like effectors and their precursors.