The functional dissection of human peripheral null cells with respect to antibody‐dependent cellular cytotoxicity and natural killing

Abstract

AbstractA null lymphocyte subpopulation was isolated from human peripheral blood using a combination of Ficoll density gradient centrifugation, chromatographic separation of immunoglobulin‐bearing cells on Sephadex G‐200‐anti‐human F(ab'), columns and E rosette sedimentation. Null cell recovery averaged 5% of total peripheral mononuclear cells with greater than 90% purity by surface marker analysis. The purified null subpopulation was markedly enriched for antibody‐dependent cellular cytotoxicity (ADCC) and natural killing (NK) activity, while the Ig+′ and E' populations were virtually inactive. In the NK assay, the number of recovered lytic units in the null subpopulation was greatly increased over the total lytic units in unf ractionated cell populations, while enrichment in ADCC lytic units was strictly dependent on the concentration of null cells in effector populations. The null cell mediators of both ADCC and NK activity were shown to lack the Ia‐like surface antigen, p 23, 30. The results suggest that both ADCC and NK are mediated by the same population of null cells comprising less than 5% of peripheral lymphocytes and which lack the Ia‐like antigen p 23, 30, as well as mature T and B cell surface markers. The marked enrichment of NK activity in purified null populations suggests that E+ T cells may regulate NK by this subpopulation in vivo.