Immune function in marathon runners

Quantitative immunoglobulins (IgG, IgA, IgM) and leukocyte phagocytosis and killing were studied in 20 male marathon runners to determine if rigorous physical conditioning affects immune function. C3, C4, Properdin Factor B, T and B cells, and phytohemagglutinin and pokeweed mitogen stimulation of lymphocytes were determined in selected runners. Complete blood counts, including platelets, were obtained for the group. Mean immunoglobulin values for IgG, IgA and IgM were within normal limits. Ten runners (50%) had slightly low total lymphocyte counts (less than 1500/mm3). Leukocyte phagocytosis and killing was consistently normal. Nine marathoners felt that running had increased, and one felt that it had decreased their resistance to respiratory infections. This could not, however, be correlated with significant changes in immune parameters. We conclude that long distance running has no effect on immune function.