Increased serum nIgM in voluntarily physically active rats: a potential role for B-1 cells

Moderate, habitual physical activity improves health, possibly because of beneficial changes in immune function. For example, physical activity can increase natural killer cell cytotoxicity, T cell proliferation, and macrophage function but has minimal impact on antigen-driven B-2-mediated immunoglobulin (Ig) responses. The following studies tested whether physical activity selectively impacts nonantigen-driven B-1-natural IgM (nIgM) but not antigen-driven B-2 Ig. Adult male, pathogen-free Sprague-Dawley rats in a barrier facility voluntarily ran in wheels from 7 to 56 days or were housed in an enriched environment for 56 days. Rats received either no antigen or keyhole limpet hemocyanin (KLH) to assess the B-2 response. Blood samples assessed serum nIgM, total IgG, total serum protein, anti-KLH IgM, and anti-KLH IgG. Physically active rats had higher serum nIgM after 7 days of running, and nIgM remained elevated over 56 days of running. In contrast, free-wheel running produced no changes in total IgG, total serum protein, anti-KLH IgM, and anti-KLH IgG. Environmental enrichment did not alter immune measures from controls. These results suggest that B-1, not B-2, cell responses are selectively impacted by physical activity. Because nIgM is important in multiple aspects of the immune response, an elevation in this innate humoral component could contribute to improved immunity in physically active organisms.