EXERCISE-INDUCED ENHANCEMENT OF IMMUNE FUNCTION IN THE RAT

Background There have been many anecdotal reports that regular, modera te exercise confers some protective immunity against infection. There has been little scientific evidence to support this. It is also unclea r whether training alters lymphocyte trafficking from the spleen to th e periphery after a bout of exhaustive exercise. Methods and Results T o determine the effect of moderate training on in vivo antibody produc tion, using rats as an animal model, we gradually trained 18 rats usin g a swimming protocol for a 4-week period after injection and booster with Keyhole limpet hemocyanin antigen. There were 9 age-matched contr ols. At the conclusion of training, both groups underwent a short-term exhaustive swim. The trained group showed marked enhancement of IgM a nd IgG production. After short-term exercise, both groups had acute ly mphocytosis, mainly T-suppressor/cytolytic and natural killer cells wi th decreases in T-helper (trained), B cells, and the T-h-to-T-s ratio. The changes in the splenocyte subsets were the opposite of the change s in the peripheral blood. With respect to function, after exhaustive exercise, there was a slight increase in mitogenesis and interleukin-2 receptor expression to concanavalin A (untrained more than trained) c ompared with controls. Conclusions Regular, moderate training enhances antibody production to specific de novo antigen both early and late. In addition, short-term exercise leads to selective release of immune cells from the spleen and results in slightly enhanced function of spl enocytes. Direct stimulation by the sympathetic nervous system and cat echolamines is the proposed mechanism for the changes seen after short -term exercise and possibly antibody production during training.