OXYGEN FREE-RADICAL GENERATION AND REGULATION OF PROLIFERATIVE ACTIVITY OF HUMAN MONONUCLEAR-CELLS RESPONDING TO DIFFERENT MITOGENS

We have compared various mitogenic stimuli for their ability to induce hydrogen peroxide (H2O2) and Superoxide anion (O-2) production by PBMC and the effect of these reactive oxygen species and hydroxyl radical (OH.) has been assessed on proliferation. Our results show that pokeweed mitogen (PWM) stimulated PBMC to release H2O2 which interfered with proliferation since inclusion of catalase enhanced PBMC thymidine uptake. In contrast, phytohemagglutinin (PHA) and monoclonal antibody to CD3 (αCD3) did not induce PBMC to generate H2O2. O-2 release by PBMC, which is readily induced by phorbol myristate acetate (PMA), did not occur when the cells were stimulated with PWM, PHA, or αCD3. In correlation, the O-2 scavenger enzyme superoxide dismutase (SOD) had no effect on the proliferative response of the cells to the same mitogens, whereas it impaired the thymidine uptake of PMA-stimulated PBMC. A regulatory role for OH. was implied by studies using a battery of OH. scavengers known to inhibit PMA-stimulated PBMC proliferation. OH. scavengers markedly inhibited the lymphoblastic transformation of αCD3-stimulated cells but had little or no effect on PHA- and PWM-stimulated PBMC. Thus, one manner by which PBMC proliferation is regulated is through oxygen free radical production which varies depending on the type of mitogenic stimulus. © 1992.