Abstract
Similar to other biological systems where the effect of nitric oxide (NO) has been examined, paradoxical findings on the effects of NO on lymphocyte function have been reported. The most paradoxical effect may be that on the one hand, NO can inhibit apoptosis, a major mechanism of down-regulation of the immune response. In this capacity, NO would serve as a facilitator of the immune response, promoting survival of effector lymphocyte populations. Yet, NO also has been shown to inhibit lymphocyte proliferation and promote apoptosis and thus effectively prevent amplification of the immune response. Therefore, the challenge in the study of the effect of NO on lymphocytes is to determine under which circumstances NO acts as a facilitator versus an inhibitor of the immune response.