The influence of incubation time and mitogen concentration on lymphocyte blastogenic response: determination of conditions that maximize population differences.

The blastogenic responsiveness of peripheral blood lymphocytes is a commonly applied measure of immune response capability. This assay is generally run under conditions of maximum lymphocyte stimulation. The purpose of this study was to evaluate which conditions of lymphocyte culture were able to best discriminate normal from subnormal lymphocyte responses to mitogens and antigens. Mitogen or antigen concentrations and the length of incubation time were varied while other assay conditions (serum supplement, lymphocyte concentration, amount of label, and length of label pulse) were kept constant. A total of 24 cancer patients and 25 normal controls were studied. Under optimal assay conditions that provided for maximum lymphocyte stimulation, we were unable to distinguish differences in response between young and old individuals or cancer patients and normal controls. However, at suboptimal mitogen/antigen concentrations or suboptimal incubation times, significant differences were observed in these populations. It is suggested that in the evaluation of lymphocyte stimulation responses in various clinical groups, suboptimal lymphocyte culture conditions may provide for maximum discrimination among the groups.