Figure 1. Representative examples of lymphocyte proliferation results. Proliferation was assayed by measuring 3H-thymidine incorporation (counts per minute [cpm]) of culture lymphocytes stimulated with different antigens and by determining the respective proliferative Indexes. The latter were calculated by dividing the cpm induced by a given antigen by the cpm induced by a negative control antigen (phosphate-buffered saline (PBS), white boxes). The proliferative index is a parameter that reflects the reactivity of a lymphocyte culture toward a given antigen. It is indicative of the cellular immunity of a person toward this antigen. The antigens used in this experiment are listed in the Table. The figure shows 3 representative culture profiles that react either with protective antigen (PA) and lethal factor (LF) (1 sample, T2), with PA only (1 sample, T9), or with none of them (41 samples, exemplified by T56). Each value is the mean of 3 independent experiments and is shown with the standard deviation (error bar). ConA, concanavalin A.