Background Exercise induces a series of changes on the immune system depending on their intensity and duration.^{1 2} In fact, transient states of immunosuppression are induced after intense physical activity³ and yet beneficial exercise anti-inflammatory effects have been described over many diseases and longevity.¹

Methods To study the impact of intense exercise for long periods of life on adaptive immunity at different ages we compared phenotypical and functional features of T lymphocytes of young (n=27) and elderly athletes (n=15) with young (n=30) and elderly non-athletes (n=30). We characterized leukocyte and lymphocyte subpopulations by flow cytometry and measured the T cell proliferation and activation response (CD69) against anti-CD3. We also studied the percentage of recent thymic emigrants (RTEs) by quantification of TREC by real-time PCR. Specific antibody titers against CMV were determined by ELISA.

Results Leucopenia was found in both groups of athletes, mainly explained by low levels of neutrophils and lymphocytes. Exercise induced higher frequencies of NK, B lymphocytes and CD8+ T cells, whereas CD4+ T lymphocytes showed significant lower levels in the elderly athletes. Moreover, young athletes showed significant differences in all parameters that define the immune risk profile (IRP), with characteristics of an aging immune system, but we did not find differences between elderly groups. Less differentiated subsets of T lymphocytes were more frequents in non-athletes, with the exception of CD8+ T lymphocytes in young individuals. The analysis of TREC content in the elderly groups showed no significant difference in either the CD4+ or CD8+ T lymphocytes. In the young non-athletes group we observe an increase in the content of TREC in CD8+ T cells, but not in CD4+ T cells. Moreover, functional response of CD4+ and CD8+ T lymphocytes was significantly impaired only in young but no in elderly athletes.

Conclusions Intensive training for long periods throughout life induces important phenotypical and functional changes on the adaptive immune response. These changes are most striking in young individuals and they damped with physiologic immune aging.