Effect of acute treadmill exercise on LFA-1 antigen expression in murine splenocytes

The LFA-1 intercellular adhesion molecule (ICAM), expressed on human and murine CD8+ and natural killer (NK) cells, participates in cytolytic interaction with target cells. This study was designed to determine whether acute exercise alters the activity of CD11a (LFA-1) on NK cells. Fourty male C3H/HeNHSD mice were sacrificed before (sedentary) or at various time points after acute treadmill exercise (30 m/min, 4 degrees slope, 30 minutes). Splenic natural killer cell activity (NKCA) was determined using a standard 51Cr release assay, using fresh splenocytes or splenocytes which had been incubated for 3 days with 100 U rIL-2. 10 micrograms/ml of mAb to LFA-1(anti-CD11a) or an equal volume of culture medium were added to the effector:target suspensions prior to 4.5 h incubation. There was a significant main effect of antibody treatment on cytolysis of tumour targets by fresh and IL-2 augmented splenocytes (p < 0.001); for both fresh and IL-2 augmented splenocytes, addition of anti-CD11a antibody reduced cytolysis of tumour target cells. Further, there was a significant main effect of exercise on fresh (p < 0.01) but not IL-2 augmented splenocytes cytolysis; this effect was due to differences in cytolytic activity between 30 and 120 minutes post exercise. Calculation of delta% in cytotoxicity showed that the capacity of mAb to CD11a to inhibit cytolysis was the lowest at 30 minutes after exercise (25%). The delta% in cytotoxicity was less pronounced in samples obtained from IL-2 augmented splenocytes, irrespective of timing of exercise. These results suggest that acute exercise renders mouse splenocytes more resistant to the blockade effect of anti--CD11a (LFA-1) and, as result, may alter killing of tumour target cells in vitro.