Circulating immune complexes in chronic eosinophilic pneumonia.

In 9 out of 14 patients with chronic eosinophilic pneumonia (CEP), followed-up in our department, circulating immune complexes (CIC) and other immunologic indices were investigated. The diagnosis of CEP was based on the typical clinical and radiographic findings and on the demonstration of eosinophilia in serum, bronchoalveolar lavage (BAL), fiberoptic transbronchial biopsies and surgical lung biopsies. CIC measured by solid-phase monoclonal RF binding were always strongly positive during a flare-up of CEP, and CIC measured by solid-phase C1q binding were also positive in most cases. Remissions of CEP were accompanied by lowering or disappearance of CIC. CIC were significantly correlated with eosinophilia (p less than 0.001 for RF and p less than 0.02 for C1q). Other immunologic indices were normal except for increased IgE in two thirds of the patients, and a slightly positive rheumafactor without rheumatic disease in half of the patients. The CIC are thus related to disease activity, and can be used as one of the markers of it, in addition to the classical markers such as eosinophilia and chest X-ray. However, this does not imply that the CIC have a pathogenetic role in CEP; these CIC can, indeed, be an epiphenomenon only.