Complement in respiratory immunopathology

Following a review of the fundamental aspects of the complement system and analytical methods, the authors discuss the pathology of complement as it relates to the respiratory system. Hereditary angioneurotic edema is a genetically transmitted deficiency in the amount or function of the C 1 esterase inhibitor. This disease is responsable for asphyxia caused by laryngeal edema, and it is now controlled by androgens. Serum complement fractional changes following challenge suggest that complement may play a role in asthma. Also, the authors have observed the presence of C 1 q, C 4, and C 3 in the bronchial mucosa in 18 cases of intrinsic asthma. Experimental studies suggest an Arthus-type phenomenon in the origin of extrinsic allergic alveolitis, with delayed onset of respiratory disorders, presence of precipitins and immune complexes, and anatomic injuries. Other respiratory diseases are dependent on similar mechanisms (rheumatoid pleurisies, collagen diseases, hyaline membrane lesions, and Good-pasture’s syndrome). Complement is thus an essential element of cellular reactions in the immune response and nonspecific inflammation in respiratory pathology.