The role of the complement system in the pathogenesis of acute pulmonary oedema produced by nephrotoxic serum in rats.

The intravenous injection of rabbit anti-rat kidney cortex serum into rats produces an acute pulmonary oedema. The first symptom to appear is dyspnoea followed by cyanosis and death. The most important pathological abnormalities were oedema and haemorrhage of the lungs. There was an apparent correlation between the onset of the acute pulmonary oedema and a drop in the total haemolytic complement titre in both normal or bilaterally nephrectomized rats. When rats were rendered complement deficient before the injection of rabbit anti-rat kidney cortex serum, the symptoms of pulmonary oedema do not appear. The nature of the mechanism through which the complement system induces these lung lesions is not yet clear. Since the vasoactive substances, histamine, 5-hydroxytryptamine and kinins or other mediators derived from leucocytes are not relevant in the pathogenesis of this lung oedema, it seems likely that the complement system acts directly.