That complement may play an important pathogenic role in some localized immune complex diseases is illustrated by studies of experimental myasthenia gravis. In this model, antibodies react with acetylcholine receptors, but the inflammatory destruction of motor end plates does not occur when complement activation is prevented. An Arthus reaction usually does not occur when a person is injected with a foreign antigen, because there is not sufficient circulating antibody against the antigen. The inflammation that develops after a booster injection of tetanus toxoid may in part be an Arthus-type reaction. X-rays of the lungs during the acute phase show interstitial edema and, occasionally, patchy infiltrates.
Lung biopsy reveals infiltration by granulocytes and lymphocytes.
Immune complex disease of the lungs also occurs in children who have received killed virus vaccines that induce antibody formation but not protective immunity, such as killed measles vaccine. When these children are later exposed to the living virus, viral antigens combine with the antibody and produce immune complex injury.