Effects of gamma-Rays on Mitogenic Response of Murine T-Lymphocyte Subsets. A Flow Cytometric Image

Flow-cytometry allows studying responses of T-cell-subpopulations stimulated in bulk-cultures without interfering cells interactions. The number and phenotype of lymphoblasts developed following stimulation with phytohaemagglutinin (PHA), anti-CD3, staphylococcal protein-A (SPA) and pokeweed mitogen (PWM) was determined in non-irradiated and irradiated samples from cell-cultures. Results showed that normal T-cells responded faster to PHA than to any of the other tested-mitogens. The peak of the PHA-response occurred on day-3, followed by anti-CD3 and SPA on day-4, and PWM-mitogen on day-5. Although PHA and anti-CD3 stimulated upon 95 % and 80 % of lymphocytes, respectively, SPA and PWM-stimulated only 40% and 30% of cells, respectively. A defective T-cell response was observed in lymphocytes cultured from irradiated-cells compared with non-irradiated cells. This loss of response was related to selective mortality of T-cells following mitogenic stimulation, due to a post-stimulation death-process. The stronger mitogens (PHA and anti-CD3)-induced death in larger proportion (50-40 %) of T-cells than weaker-mitogens such as SPA and PWM (30-20 %) and that process affected different lymphocyte-subsets to different extents. Post-stimulation death occurred more frequently in total CD8+ and CD45RO+ T-cells compared with CD4+ and CD45RA+ T-cells, but memory CD4+, CD45RO+ T-cells were the population most severely affected in samples from irradiated-cells. Whether this death-process is due to apoptosis or other mechanism(s) need further investigations.