BIOCHEMICAL-CHARACTERIZATION OF A GLUCOCORTICOID-INDUCED MEMBRANE-PROTEIN (RM3 1) IN HUMAN MONOCYTES AND ITS APPLICATION AS MODEL SYSTEM FOR RANKING GLUCOCORTICOID POTENCY/

Purpose. Upon glucocorticoid stimulation, human mononuclear leucocytes express an antigen, RM3/1, which characterizes a subpopulation of hum an monocytes and macrophages evolving in late phase of inflammation. W e investigated biochemical properties of the RM3/1 antigen and correla tions between antigen expression and glucocorticoid potency. Methods. Biochemical properties were analyzed after solubilization by immunoaff inity methods and SDS-PAGE. Results. Induction of the RM3/1 antigen is a glucocorticoid receptor mediated process, in contrast, inflammatory mediators such as LPS or TPA were not able to upregulate RM3/1 expres sion. After SDS-PAGE, the antigen appeared as a 130 kDa (nonreduced)/1 50 kDa (reduced) glycoprotein with a 25 kDa N-linked glycoportion. The interdependence between antigen density and glucocorticoid efficacy w as assessed by calculation of relative antigen expression induced by d examethasone, fluticasone propionate, budesonide, triamcinolone aceton ide, flunisolide, beclomethasone, prednisolone and triamcinolone. Rela tive antigen expression was significantly correlated with the relative receptor affinity of the glucocorticoid. Conclusions. We described bi ochemical properties of the glucocorticoid-induced protein RM3/1. Thou gh the precise role of the RM3/1 antigen in the antiinflammatory proce ss is not fully understood yet, an useful application of the induced e xpression could already be demonstrated for pre-clinical screening of glucocorticoid potency.