Postexercise immune correlates in children with and without cystic fibrosis

Previous studies have shown that children with cystic fibrosis (CF) are capable of mounting a normal immune response after the stress of exercise. However, few data are available regarding the underlying mechanisms by which this immune modulation occurs.

In this study, lymphocyte and leukocyte cell counts were measured before and immediately after a single bout of exhaustive exercise in 25 children (ages 8-17 yr; 12 with CF and 13 healthy controls). Catecholamine, cortisol, and insulin levels, age, nutritional parameters, and static and dynamic lung function were measured as potential correlates for immune modulation. We hypothesized that catecholamine levels would be associated with the immune changes seen after exercise in children with CF.

Our results demonstrated positive correlations between age and the change in cell counts after exercise for white blood cells (r = 0.44, P < 0.03), lymphocytes (r = 0.60, P < 0.002), monocytes (r = 0.43, P < 0.03), and CD3-CD16+CD56+ cells (r = 0.61, P < 0.002). Lower increases in the lymphocyte and CD3-CD16+CD56+ cells were observed in the CF group. Changes in pre- and post-exercise norepinephrine levels were weakly correlated with the changes in granulocyte, lymphocyte, and monocyte cell counts. Changes in cortisol levels correlated with lymphocyte and CD19+ cell count changes for the CF group but not for the healthy controls. Within the CF group, the severity of lung disease (as indicated by a FEV1) was negatively correlated with changes in lymphocyte (r = -0.66, P < 0.02) and CD3-CD16+CD56+ cell counts (r = -0.67, P < 0.02).

The results suggest that postexercise changes in cell counts occur in an age dependent, norepinephrine associated manner. Disease severity for children with CF also appears to enhance the postexercise leukocytosis with pronounced increases seen in natural killer cells.