Physical exercise modulates the cellular immune system in patients with rheumatoid arthritis

The recent findings that bicycle exercise training may reduce the number of swollen joints in patients with rheumatoid arthritis (RA) stimulated us to examine the possibility that this was mediated through exercise‐induced immunomodulation. The effect of a single bout of physical exercise on blood mononuclear subsets, proliferative responses and natural killer (NK) cell activity was determined. Six patients with moderately active RA for 20 years exercised for 27 min on a bicycle, the work intensity being estimated at 68% of max V̇O_2max. Blood samples were collected before and during the last minutes of exercise, as well as 2 h afterwards. During bicycle exercise the proportion of T cells (DC3+ cells) declined, mainly because of a fall in T helper cells (DC4+ cells). The proportion of NK cells (CD16+ cells) increased during work, but reverted afterwards. The monocytes (CD14+ cells) did not change; B cells (CD20+ cells) declined slightly during exercise and reverted later. No change in PHA‐, PPD‐ and Unstimulated BMNC proliferation occurred during exercise. Two hours after exercise, PPD‐ and IL‐2‐induced proliferation increased significantly, except for the PHA‐stimulated response. The NK cell activity increased only significantly during exercise when the cells were preincubated with indomethacin, and returned to normal 2 h afterwards. This shows that brief, moderate exercise by patients with RA alters the composition of blood mononuclear cell subsets and cell functions. The clinical significance of this immunomodulation remains to be elucidated.