MODIFIED LIMITING DILUTION ASSAY FOR CELL SYSTEMS

A form of mathematical analysis that permits an extended analysis of l imiting dilution assays under conditions in which accessory factors or cells are limiting is presented. This is in contrast to the tradition al form of analysis that permits only a single limiting parameter. Bot h make use of in vitro experiments to determine the number of antibody -producing cell precursors; the traditional form of analysis requires that all accessory cells or their factors be present in saturating con centrations, whereas in the analytic method employed here, not only B cells, but accessory cells (macrophages) or their factors are limiting . Analysis under nonsaturating conditions permits greater elucidation of the mechanisms of intercellular interaction.