Mobilization and Fcγ-Receptor Expression of Six NK Cell Subsets During and After Acute Exercise

Abstract

Natural killer (NK) cells are the most responsive lymphocytes during acute exercise, with increased concentrations. After exercise, NK cell levels drop below their resting level if the exercise intensity was high, but values usually recover within 1-3 hours. NK cells may be divided into CD56dim and CD56bright subsets. The CD56dim subset is the major population, representing about 80% of NK cells. Smaller subpopulations were recently studied for cell developments and diseases. We previously reported that exercise decreased the expression of Fcγ-receptor III (CD16); however, it is not yet understood how exercise affects these small subsets. PURPOSE: To clarify the effect of acute exercise on the mobilization and expression of CD16 on the six different NK cell subsets. METHODS: Healthy male students (n=6, 22.8±0.8 years old) exercised on a cycle ergometer for 30 min at intensities corresponding to the individual’s onset of blood lactate accumulation (70-85% maximum oxygen consumption). Venous blood samples were collected at rest (PRE), just before the end of exercise (END), 30 (POST 30), 60 (POST 60), 120 (POST 120), and 180 (POST 180) min after exercise. Cell counts and proportions of total lymphocytes expressing CD16-CD56bright (R1), CD16+CD56bright (R2), CD16-CD56dim (R3), CD16dimCD56dim (R4), CD16brightCD56dim (R5) and CD16brightCD56- (R6) subsets were determined. CD16 expressions of these subsets were also examined by flow cytometry. ANOVA was used for statistical analyses. RESULTS: Exercise induced changes in NK cell concentration in CD56dim (R3, p=0.04; R4, p<0.01; R5, p<0.01) and CD56- (R6, p<0.01) subsets. However significant changes between time points were only found in R5. In this subset, NK cell counts increased from PRE (356±151 cells/μL) to END (1182±159 cells/μL, p<0.01) and decreased under the PRE-level at POST 30 (108±27 cells/μL, p<0.01) and POST 60 (106±70 cells/μL, p<0.01). There were no changes in CD56bright (R1, R2) subsets. These cell mobilizations were reflected in proportions to the total lymphocyte count. Expressions of CD16 were down-regulated at END in R5 (-502±135, p<0.01) and R6 (-416±99, p<0.01) then recovered at POST 30. CONCLUSIONS: These results suggest that the influence of acute exercise on NK cell mobilization and CD16 expression are clear in subset R5, but not in R1 and R2.