DEFECTIVE MONONUCLEAR PHAGOCYTE FUNCTION IN SYSTEMIC LUPUS-ERYTHEMATOSUS - RELATIONSHIP OF FCRII (CD32) WITH INTERMEDIATE CYTOSKELETAL FILAMENTS

To investigate the mechanisms of impaired Fc receptor-mediated mononuc lear phagocyte system (MPS) clearance in systemic lupus erythematosus (SLE), we have examined FcRII (CD32) and vimentin function in 25 patie nts with SLE and 36 healthy adults. In SLE, FcR-mediated phagocytosis of IgG-sensitized bovine erythrocytes was decreased (5.9 +/- 2.47 vs. 8.3 +/- 3.59 erythrocytes phagocytosed/monocyte/h; p < 0.05), and CD32 and vimentin expression was within the normal range; however, the per centage of simultaneously CD32+ and vimentin+ cells was increased (30 +/- 12 vs. 20 +/- 13; p < 0.05). Circulating immune complexes (CIC) we re positive in 11 SLE patients, and levels were positively correlated with proteinuria (r = 0.53; p < 0.05) and disease activity (r = 0.40; p < 0.05). The mobility of membrane molecules, measured as the percent age of patients that showed patching and/or capping of CD32, was incre ased compared with controls, but not significantly (p < 0.1). At the s ame time, redistribution of vimentin filaments was observed. In conclu sion, our data seem to support the possibility of a functional and/or structural alteration in the relationship between Fc receptors and int ermediate cytoskeletal filaments as a causative factor in the deficien t internalization of ligands bound to Fc receptors in monocytes of SLE patients.