Improved quantification of cellular cytotoxicity reactions: determination of kinetic parameters for natural cytotoxicity by a distribution-free procedure.

A distribution-free statistical procedure for estimating kinetic parameters for cellular cytotoxicity reactions is described. Estimates of cytotoxic activity obtained using this procedure are considerably more precise than percent cytotoxicity values, lytic unit values, and V max values determined by least-squares analysis of the same sets of experimental data. Application of this procedure to the study of natural cytotoxicity allows for precise quantitative comparisons of the lytic activity of different lymphocyte preparations for a given target cell line, of a single lymphocyte preparation for different target cell lines, or of a given lymphocyte and target cell combination under different experimental conditions. This procedure, which does not involve a more complex experimental protocol than other methods, should also allow for more accurate assessment of the relative cytotoxic activity of lymphocytes obtained from patient populations.