Exercise induced augmentation of cellular and humoral autoimmunity associated with increased cardiac dilatation in experimental autoimmune myocarditis

Summary: To determine the effects of exercise in experimental autoimmune myocarditis, Guinea pigs immunised with heterologous heart protein (rat heart), Freund's complete adjuvant, and pertussis vaccine (treated group) were exercised on a treadmill for a total of 11 weeks and compared with non-exercise treated animals. In vivo heart rates and pressures, in vitro left ventricular pressure-volume relations, myocardial histology, circulating antiheart antibody, and in vitro lymphocyte stimulation were determined. Exercise resulted in increased cardiac dilatation in treated animals as assessed by in vitro left ventricular pressure-volume relations compared with non-exercise treated animals (at 8 mmHg 1.41(0.17) ml·kg^-1 vs 1.20(0.17) ml·kg^-1 respectively, p<0.005). Exercise also resulted in increased concentrations of circulating antiheart antibody as assessed by radioimmunoassay (0.14(0.04) μg vs 0.10(0.03) μg respectively, p=0.01), and increased lymphocyte activation to specific antigen (stimulation index 3.7(0.07) vs 2.4(1.0) respectively, p<0.001). Despite the associated augmentation of autoimmunity with cardiac dilatation, there were no differences in the histopathological findings between the exercised treated and the non-exercised treated animals either qualitatively or quantitatively (number of inflammatory cell microaggregates). this finding suggests that, although the immune system is important in experimental autoimmune myocarditis, the amount of inflammation and necrosis does not appear to correlate with the degree of left ventricular dilatation and presumed dysfunction.