Late allergic bronchial reactions and the effect of allergen provocation on the complement system.

Forty-nine bronchial provocations were performed with different allergens in allergic asthmatic patients. Immediate bronchial reactions occurred in 33 instances, and late reactions occurred in nine instances. The material was divided into three groups according to patients with no reactions, patients with early reactions alone, and patients with late reactions. Titers of whole complement and factors C2 and C3 were determined hemolytically, and the serum protein contents of factors C3, C4, and C1q were measured immunochemically. Decreases in complement and complement components were observed on a number of occasions after bronchial challenge. When the groups were compared with respect to mean change in complement titers, the three groups were indistinguishable. No change was noted in the ratio between the complement contents in venous and arterial blood as a result of provocation, nor did the specific hemolytic activity of factor C3 change. No C3 split products could be traced. It is likely that there will be a higher proportion of patients with C2 consumption among those with late bronchial reactions. No special feature could be assigned to these individuals, however. It is concluded that no major complement activation is regularly found in allergic asthmatic patients as a result of exposure to allergens. However, groups of patients in whom such activation takes place might exist.