Background: The interactions between CD40 and its ligand, CD40L, control humoral and cell-mediated immune responses. CD40 ligation may promote asthma-associated inflammatory responses in the airways. Many reports confirm the inflammatory basis of exercise-induced bronchoconstriction (EIB) in asthmatics.

Methods: The study was conducted in a group of 19 asthmatic patients (11 with EIB, 8 without EIB) and 8 healthy volunteers. We analyzed the changes in plasma concentrations of soluble CD40 ligand (sCD40L) and soluble P-selectin (sP-selectin) induced by intensive exercise.
We also studied possible correlations with the results of measurements commonly associated with asthmatic inflammation.

Results: The study revealed statistically significant higher baseline concentrations of sCD40L–but not sP-selectin–in the group of asthmatics with EIB than in those without. In the asthmatic patients with EIB, sCD40L and sP-selectin concentrations increased significantly 30 minutes after exercise and returned to baseline 24 hours after exercise. Baseline concentrations of sCD40L correlated with baseline sP-selectin or
fractional exhaled nitric oxide concentration (FENO), an increase in sP-selectin 30 minutes after exercise, and changes in FENO or bronchial hyperresponsiveness 24 hours after exercise. A statistically significant correlation between an increase in sCD40L concentrations 30 minutes after exercise and an increase in FENO 24 hours after exercise or baseline eosinophil cationic protein was observed.

Conclusion: After exercise in the group of allergic asthmatics with EIB, upregulation of CD40L by increased expression of inflammatory
molecules and improved sensitivity of CD40-responsive cell types to the effects of proinflammatory cytokines may play an important role in the increased airway infl ammation observed after postexercise bronchoconstriction.

Key words: Asthma. Exercise-induced bronchoconstriction. sP-selectin. sCD40 ligand. Airway inflammation.