Lymphocyte Apoptosis, Adhesion/activation Molecules And Complement Regulatory Proteins Following Intensive, Moderate And Eccentric Exercise

Abstract

Exercise elicits an initial increase in the number of blood lymphocytes, followed by a rapid lymphocytopenia in the recovery phase. Alterations in cell phenotype accompany changes in lymphocyte number. The mechanisms underlying these changes and their potential functional consequences are not understood. PURPOSE To examine the effects of intensive, moderate and eccentric exercise on lymphocyte apoptosis, and lymphocyte expression of the complement regulatory proteins CD55 (DAF) and CD59 (MACIF), and the adhesion/activation molecules CD18 (β2 integrin), CD53 and CD54 (ICAM-1). METHODS Eight trained males (Age: 28 ± 5 yrs,: VO2max 63 ± 3 ml-kg·min−1) completed three treadmill running protocols: (1) an intensive protocol at 80% VO2max, (2) a moderate protocol at 60% VO2max, and (3) a −10% eccentric protocol at 80% VO2max. Blood samples were taken before exercise, immediately after, 1h and 24h later. Isolated lymphocytes were assessed for markers of apoptosis (Annexin-V, HSP60 and CD95) and expression of CD proteins using flow cytometry. RESULTS No lymphocyte apoptosis was found after any of the running protocols. Using CD55, CD59, CD18 and CD53 monoclonal antibodies, two populations of lymphocytes with strikingly different fluorescent intensities (“dim” or “bright”) were found. Together these accounted for >98% of lymphocytes. An increase in the percentage of CD55dim, CD59dim, CD18bright, CD53bright and CD54+ cells occurred immediately after the intensive protocol, before falling below baseline at 1h post-exercise (p<0.05). The phenotypes of lymphocytes at 24hr closely resembled those found pre-exercise. The eccentric protocol at the same relative intensity produced similar results. No significant changes in lymphocyte phenotype were observed following the moderate protocol (p>0.05). Two-colour analysis of lymphocyte subsets showed that increases in CD8+ T-lymphocytes and CD3−/CD56+ Natural Killer (NK) cells immediately after the intensive protocol, and their subsequent fall within 1 hr account for the changes in CD55dim, CD59dim, CD18bright CD53bright and CD54+ populations. No changes in CD4+ T-lymphocytes were found. CONCLUSION Apoptosis affecting blood lymphocytes does not contribute to post-exercise lymphocytopenia. Intensive treadmill running results in the appearance in the blood of additional CD8+ T lymphocytes and CD3−/CD56+NK cells. Lymphocytes expressing high levels of cell surface adhesion/activation molecules appear to exit the blood within 1h post exercise. The basis of selection of lymphocyte subsets for recruitment into the blood, and their fate after exercise-induced extravasation requires investigation.