Lymphocyte proliferation in response to exercise

Lymphocyte proliferative responses are often used to evaluate the functional capacity of the immune system in response to exercise. Blood mononuclear cells (BMNC) are stimulated in vitro with polyclonal mitogens and the incorporation of ³H-thymidine into the DNA reflects cell proliferation. The BMNC are most often stimulated with either phytohaemagglutinin (PHA), poke weed mitogen (PWM), concanavalin A (Con-A), interleukin-2 (IL-2), or purified derivative of tuberculin (PPD). The literature concerning lymphocyte proliferation and exercise is reviewed with respect to the type and intensity of exercise, and also the effect of training status. The proliferative responses to exercise are highly heterogeneous, the most consistent finding being that PHA-stimulated cell responses decrease during exercise which may reflect a decreased fraction of CD3+ cells. In contrast, reduced, elevated or even unchanged lymphocyte proliferative response to PHA, PWM, Con-A, IL-2 and PPD have been demonstrated in the recovery period following exercise. Also variable responses are present in trained athletes compared to less fit subjects. Even though this may reflect that the time of ³H-thymidine incorporation into lymphocytes varies, we conclude that a functional evaluation of the immune system in response to exercise cannot be based solely upon measurements of lymphocyte proliferation.