Complex pattern of the myelo-monocytic differentiation antigens MRP8 and MRP14 during chronic airway inflammation

One of the characteristics of cystic fibrosis is the presence of the so-called cystic fibrosis antigen in the plasma of patients. The CF-antigen has been shown to consist of the two calcium-binding proteins MRP8 and MRP14. In the present study we investigate first whether elevated plasma titers of MRP8 and MRP14 are linked to the primary defect of CF or are rather a result of chronic airway inflammation; and second, whether the known complexes of these proteins may have in vivo relevance during inflammation. By employing the ELISA technique we measured MRP8 and MRP14 levels in the plasma of patients suffering from CF or nonspecific chronic bronchitis (CB) and of healthy controls, in sputum of CF and CB patients, and in saliva of CF patients and healthy controls, respectively. We found elevated plasma concentrations of both proteins in CF and CB patients compared to healthy controls. Levels correlated significantly with systemic and local signs of disease activity (i.e. c-reactive protein (CRP), daily sputum production). MRP8 and MRP14 both were found in high amounts at similar concentrations in sputum of CF and CB patients and, to a lesser extent, in saliva of CF patients and healthy donors. After covalent cross-linking at least three different complexes composed of MRP8 and MRP14 with approximate molecular weights of about 25, 35 and 48 kDa were detected in all samples. From this we conclude that the elevated plasma levels of MRP8 and MRP14 in CF and CB are the result of inflammatory processes. Further, possible biological functions of these proteins seem to be associated with complexed forms of MRP8 and MRP14 rather than with individual proteins.