STRENUOUS EXERCISE AND IMMUNOLOGICAL CHANGES - A MULTIPLE-TIME-POINT ANALYSIS OF LEUKOCYTE SUBSETS, CD4 CD8 RATIO, IMMUNOGLOBULIN PRODUCTION AND NK CELL RESPONSE/

This study was designed to examine the impact of exhaustive endurance exercise on a number of immune parameters of physically fit male subje cts (VO(2)max 66.5 +/- 5.3 ml/min/kg) who performed treadmill exercise at 65 % of their VO(2)max for 120 min. Serial blood samples were take n before, during and after exercise and changes in leukocyte and lymph ocyte subset concentrations; immunoglobulin production in vitro; and n atural killer (NK) cell response were measured. The exercise regimen w as found to induce the well-known phenomenon of leukocytosis which con sisted primarily of a granulocytosis and lymphocytosis. Among the lymp hocyte subsets, peripheral pan T cells (CD3(+)) as well as helper (CD4 (+)) and suppressor (CD8(+)) T cells were found to be elevated. A rela tively smaller increase in CD4(+) than CD8(+) cells resulted in depres sed CD4/CD8 ratios throughout-the exercise period. After exercise, T c ells declined progressively a nd, 2 h postexercise, were less than 60 % of their pre-exercise level. In contrast, the CD4/CD8 ratio demonstr ated a progressive increase, thus representing a reversal in the patte rn observed during exercise and a trend towards an elevated ratio duri ng recovery. B cells (CD19(+)) were relatively unaffected by exercise, although IgM production by pokeweed mitogen-stimulated lymphocytes ob tained from blood samples after 120 min of exercise was significantly depressed. NK cells were affected dramatically by exercise. Both CD16( +) cell numbers and NK cytotoxicity were increased during exercise, fo llowed by a persistent depression in the postexercise period. The stre nuous exercise induced a profound effect on NK cells as evidenced by a 40 % depression of the NK cell count for as long as 7 days after the cessation of exercise. Our results provide direct kinetic evidence dem onstrating that exhaustive exertion alters both lymphocyte distributio n pattern and effector function, suggestive of possible exercise-induc ed immune compromise, particularly in the post-exercise recovery perio d.