Acute Pulmonary Injury Induced by Immune Complexes

Abstract

The response to the intratracheal administration of heterologous and homologous immune complexes formed in the zone of antigen-antibody equivalence was examined in the rat. Small doses of immune complexes, 40 or 100 μg, were rapidly phagocytosed by bronchoalveolar macro-phages and did not provoke an inflammatory response. Larger doses, 1 or 3 mg, produced a focal acute hemorrhagic alveolitis which was maximal at 6 hr and resolved by 4 days. At the height of the reaction complement and unphagocytosed complexes were detected by immunofluorescence in the airspaces and pulmonary interstitium. Immune complexes were also detected in the draining lymph nodes and spleen up to 48 hr after instillation. The acute reaction was abolished in animals depleted of complement by cobra venom factor. Late changes, in particular granu-lomas or fibrosis, could not be demonstrated following a single administration of immune complexes.