Interferon-induced NK augmentation in humans. An analysis of target recognition, effector cell recruitment and...

By combining a single-cell cytotoxicity assay in agarose with estimations of the maximal natural killer (NK) cell potential (Vmax) by 51Cr release, the mechanism behind interferon augmentation of human NK cells were analysed. The number of target-binding cells (TBCs) the fraction of active TBCs and NK cell recycling were studied after short-term interferon treatment. The results demonstrate a dual effect of interferon on human NK cells: effector cell recruitment and increased effector cell recycling. Both of these variables were increased when NK cells were tested against the standard target K-562 and against Daudi and BJAB cells, derived from B-type lymphomas. However, when T cell lines derived from acute lymphocytic leukaemia (Molt-4 and 1310) were used as targets, a larger fraction of active NK cells were found among untreated TBCs, whereas interferon treatment only resulted in increased effector cell recycling and not in effector cell recruitment. No increase in TBCs after interferon treatment could be detected with any cell line tested. The difference seen between T and non-T cell lines with regard to interferon-induced effector cell recruitment is discussed in relation to known characteristics of the human NK system.