Effects of Exercise on the Macrophage MHC II Response to Inflammation

The purpose of this investigation was to determine the effects of different doses of exercise on the ability of Propianibac-terium acnes (P. acnes) to induce major histocompatibility complex (MHC) II antigen expression on macrophages (Mφ's). Pathogen-free male Balb/c mice were exercised on a treadmill moderately (MOD, 15 - 17 m/min, 5 % grade, 30 min/day) or exhaustively (EXH, 15 - 40 m/min, 5 % grade, 2 - 4 hr/day) for a period of 7 days during P. acnes-induced inflammation. A control group (CON) consisted of animals exposed to the treadmill environment and handling. Sub-optimal (0.03 mg/g b. wt., i.p.) and optimal (0.08 mg/g b.wt.) doses of P. acnes were used to increase Mφ MHC II expression. Animals were sacrified on Day 7 and Mφ's were harvested by peritoneal lavage. Direct imimuno-fluorescent staining was performed by incubating perittoneal exudate cells (10⁶) with an FITC-labeled anti-mouse MHC II (I-A^d) antibody. Basal expression of MHC II was not affected by exercise. There were no significant differences among the groups in the percentage of M0's expressing MHC II at any dose of P. acnes. However, EXH significantly (p<0.05) suppressed the expression (mean fluorescent intensity, MFI) of MHC II when compared to MOD (37.1 ± 1.95 [mean ± sem] vs 49.1 ± 2.15, p < 0.05) at the suboptimal P. acnes dosage. At the optimal P. acnes dose, both MOD and EXH significantly suppressed (27 ± 1.6, 25 ± 2.2 and 41.5 + 3.2, for EXH, MOD, and CON, respectively, p < 0.0001) P. acnes-induced Mφ MHC II MFI. Plasma corticoster-one was highly (r = - 0.71, p = 0.001) inversely correlated with Mφ MHC II expression. However, exercise failed to afffect P. acnes-induced production of interferon-γ. These data suggest that, dependent on the degree of stimulation, exercise can negatively affect Mφ expression of MHC II, an effect that may be detrimental to the Mφ's ability to present antigen to T lymphocytes.

Key words

Mice - P. acnes - interferon-γ - corticosterone - exercise - immunity