Exercise increases prolactin-receptor expression on human lymphocytes.

Plasma prolactin has been shown to increase during stress; the immune system is responsive to prolactin and affected by stress. Therefore, this study was undertaken to investigate the effects of acute graded, maximal treadmill exercise on prolactin-receptor expression by lymphocytes. Eight healthy men underwent one exercise and one nonexercise session. Blood was sampled immediately before and after the exercise. On the day of the nonexercise session, two resting blood samples were obtained at the same times as the exercise session samples to act as baseline data. Plasma prolactin concentrations were significantly elevated in response to exercise and correlated positively with total prolactin-receptor expression per B lymphocyte. An increase in total prolactin-receptor expression per B lymphocyte in response to exercise also was observed. In addition, exercise significantly increased the total number of circulating B lymphocytes expressing prolactin receptor as well as the total number of circulating B lymphocytes. These data support the idea that exercise may enhance the interaction between immune target cells and prolactin, a stress hormone capable of enhancing immune function.

Effects of resistance training on resting immune parameters in women.

The aim of this investigation was to determine whether intense resistance training of 6 months duration influenced resting immune parameters. Previously untrained women underwent one of four training programs or were non-training controls (CON, n=7). The resistance-training groups trained for total body power (TP, n=16), total body hypertrophy (TH, n=18), upper body power (UP, n=15) or upper body hypertrophy (UH, n=15). Immune parameters were measured from a fasting morning blood draw in September/October (0 months, t(0)), November/December (3 months, t(3)), and April/May (6 months, t(6)). Lymphocyte subsets [CD4+ T cells, CD8+ T cells, natural killer cells (NK), and B cells], and mitogen-stimulated proliferation were measured. The concentration of NK cells increased ( P<0.001) after 3 months of training for the resistance-training groups but not the CON group. This increase was not present after 6 months of training, thus it was a transient change. Lymphocyte proliferation responses were similar across time for the resistance-trained and CON groups for all stimulation conditions. Thus, resistance training induces a transient increase in NK cells but has little effect on lymphocyte trafficking or proliferation. This was consistent despite differences in the volume of muscle mass trained or the manner of training (power verses hypertrophy).