Qualitative and quantitative analysis of subpopulations of cytotoxic effector cells by flow cytometry

The heterogeneous nature of cytotoxic effector cells presents a difficult obstacle to the study of developmental, biochemical and molecular events governing cytotoxic T lymphocytes (CTL) and natural killer (NK) cell biology. In previous studies, there were no available methods, other than the single cell assay or micromanipulation techniques that could distinguish between lytic and non-lytic cells present in purified populations or clones. Further, there were no available means to isolate these subsets for further investigation. The studies presented here describe a novel approach to identify and isolate cells based on their functional characteristics. Thus, non-lytic free and conjugate forming cells as well as killer cells could be identified, quantified, and further purified by flow cytometric cell sorting for further investigations. Studies of several properties of isolated NK subpopulations (free, non-lytic binders, and killers) are presented.