Complement changes during exercise-induced asthma

Two groups of asthmatic children, one with and one without a history of post-exercise wheezing, and one non-asthmatic adult, were exercised on a treadmill, and their complement levels were measured before and after exercise. The first group of patients had the most obvious fall in FEV 1 and all showed a slight rise in haemolytic complement following exercise. Two of the patients of the second group also had a rise in haemolytic complement. The C4 titre did not change in any of the asthmatic children who did not wheeze after exercise, but there were changes, albeit inconsistent, in the titres of C4 in four of the six patients who exhibited post-exercise wheezing. C3 breakdown products were not detected in any of the sera, following exercise. The role of complement in exercise-induced bronchospasm is not clear, but there does appear to be a greater lability of the complement system in patients who are susceptible to this form of provocation.