RESUMO
<p><b>BACKGROUND</b>Both athletes with intensive exercise and aged people may have weakened immunity against virus infection. This study aimed to evaluate whether people undergoing aerobic exercises including competitive cyclists with moderate training (CMT) and middle-aged people practicing Tai Chi Chuan (TCC) exercise have higher immunity against hepatitis B virus than age-matched sedentary controls including college students (CSC) and middle-aged people (MSC).</p><p><b>METHODS</b>Human peripheral blood mononuclear cells from competitive cyclists and sedentary controls were stimulated by phytohemagglutinin (PHA) to prepare conditioned medium (MNC-CM) for the assessment of inhibitory effects on hepatitis B surface antigen (HBsAg) expression in human hepatoma Hep3B cells.</p><p><b>RESULTS</b>The inhibitory effects on the relative HBsAg expression of CMT's and TCC's MNC-CM were greater than those of the controls. The CMT's MNC-CM prepared from 5 microg/ml PHA decreased HBsAg expression to 61.5%, whereas that of CSC remained at 83.8%. Similarly, this expression by treatment of TCC group' MNC-CM was 68.4% whereas that of MSC group was 84.3%. The levels of cytokines such as interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), IFN-alpha and interleukin-1beta (IL-1beta) in the MNC-CM from the CMT and TCC groups were greater than those in the controls. Antibody neutralization of CMT's MNC-CM and addition of recombinant cytokines into CSC's MNC-CM indicated that IFN-gamma, TNF-alpha and IFN-alpha had synergistic effects against HBsAg expression. Similar blocking effect was noted in TCC versus MSC groups.</p><p><b>CONCLUSION</b>These results suggest that the immunomodulatory response to suppress HBsAg expression in CMT and TCC with moderate aerobic exercise is greater than that in age-matched sedentary controls.</p>