PROBIT ANALYSIS OF CYTOTOXICITY DATA

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Abstract
The cytotoxicity method of Pincus and Gordon was used for detecting H-2 specificities on cultured L1210 [mouse leukemia] cells and mouse spleen lymphocytes. For the typing of DBA/2 spleen lymphocytes, guinea pig serum was used as the source of complement; for L1210 cells, a 1:1 mixture of rabbit and mouse serum was used. Assays using different sources of complement were compared and the confidence level for each group of tests was indicated. The most significant source of variation in these cytotoxicity assays was complement. Thus, probit transformation, by normalizing the data to fit a straight line whose slope provides an index of heterogeneity in probits/unit dilution, places the assay within known limits of variation. Conversely, the SD or SE is the reciprocal in log10 dilution units. This type of information allows a quantitative comparison of day to day test performance and an accurate assessment of the variables in test performance vs. differences in reagents. Probit transformation is a simpler method with more applicability (because of the derived statistical information) than the Von Krogh analysis as developed by Reif. It can be used in immunological assays, such as skin graft rejection, tumor survival data and radioimmunoassay determinations. This method of probit analysis was also used in studying synchronous cell cultures.