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 mononuclear phagocyte system (MPS) clearance in systemic lupus erythematosus (SLE), we have examined FcRII (CD32) and vimentin function in 25 patients 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 percentage of simultaneously CD32+ and vimentin+ cells was increased (30 +/- 12 vs. 20 +/- 13; p < 0.05). Circulating immune complexes (CIC) were 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 percentage of patients that showed patching and/or capping of CD32, was increased compared with controls, but not significantly (p < 0.1). At the same time, redistribution of vimentin filaments was observed. In conclusion, our data seem to support the possibility of a functional and/or structural alteration in the relationship between Fc receptors and intermediate cytoskeletal filaments as a causative factor in the deficient internalization of ligands bound to Fc receptors in monocytes of SLE patients.
Vázquez-Doval
J
J
Department of Immunology, School of Medicine, University of Navarra, Pamplona, Spain.
Sánchez-Ibarrola
A
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D000936:Antigen-Antibody Complex / Q000097:blood; D005260:Female; D006801:Humans; D007152:Immunologic Capping; D007382:Intermediate Filaments / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000276:immunology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010586:Phagocytes / Q000502:physiology*; D010587:Phagocytosis; D017452:Receptors, IgG / Q000032:analysis*; D014746:Vimentin / Q000032:analysis*
D000936:Antigen-Antibody Complex; D017452:Receptors, IgG; D014746:Vimentin