SOLUBLE COMPLEMENT RECEPTOR-TYPE 1 (CD35) IN BRONCHOALVEOLAR LAVAGE OF INFLAMMATORY LUNG-DISEASES

Complement receptor type I (CR1) (CD35; C3h/C4b receptor) is a transme mbrane protein of many haematopoietic cells, Once cleaved, soluble com plement receptor type 1 (sCR1) exerts opposite effects as a powerful i nhibitor of complement, This study addressed both the question of whet her sCR1 was found in bronchoalveolar lavage (BAL) of normals and pati ents with various inflammatory disease, and its possible origin. In th is retrospective study covering specimen and clinical data of 124 pati ents with acute and chronic inflammatory lung pathologies, BAL superna tants were analysed by enzyme-linked immunosorbent assay technique for sCR1. Correlations were made between the sCR1 levels obtained and the constituents of BAL. Human alveolar macrophages were cultivated in or der to determine their secretory capacity of sCR1, Alveolar macrophage s from normal subjects were shown to release sCR1 in vitro. In additio n, sCR1 was present in BAL of normal controls and was significantly in creased in acute inflammatory lung diseases such as acute respiratory distress syndrome (ARDS), bacterial and Pneumocystis carinii pneumonia , as well as in chronic inflammatory diseases such as interstitial lun g fibrosis and sarcoidosis, In BAL of ARDS, bacterial, and P. carinii pneumonia, there was a good correlation between sCR1 and the absolute neutrophil counts,In sarcoidosis, a correlation was found with BAL lym phocyte counts, Serum sCR1 was not increased in patients compared to c ontrols, Soluble complement receptor type 1 (sCR1) is found in the bro nchoalveolar lavage in health as well as in acute and chronic inflamma tory disease, Alveolar macrophages are capable of releasing sCR1 in vi tro and may be the main physiological source of sCR1 in the alveoli, T he good correlation between sCR1 and the absolute neutrophil or lympho cyte numbers in bronchoalveolar lavage of inflammatory diseases sugges ts a predominant role of leucocytes for the release of sCR1 in such co nditions, The release of this inhibitor of complement may be crucial t o control and reduce complement activation and thus prevent lung injur y.