Application of laser cytometry to the analysis of immunologically induced in vitro lymphocyte responsiveness

This study defines an assay (laser analysis) that is a significant advance in our ability to quantitate and analyze immunologically induced in vitro lymphocyte responsiveness. Laser analysis is demonstrated to parallel radionucleotide incorporation (3H-thymidine) in terms of kinetic pattern, dose response characteristics, and statistical accuracy while exeeding radionucleotide incorporation in sensitivity. Direct quantitation of lymphocyte responsiveness, in terms of cellular proliferation, disclosed that substantial numbers of small lymphocytes were produced during in vitro stimulation with mitogen (concanavalin A) or antigen (streptokinase-streptodornase) in addition to the expected increase in lymphoblasts. The magnitude of this "total cellular response" (lymphocytes plus lymphoblasts) was found to be similar for antigen and mitogen stimulation, a finding not suggested by routine radionucleotide incorporation or morphological assays.