[Decreased FcγRIIb1 translocation to lipid raft signaling domains in activated B lymphocytes from patients with systemic lupus erythematosus].

OBJECTIVE:To observe the changes in FcγRIIb1 translocation to lipid raft signaling domains in activated B lymphocytes from patients with systemic lupus erythematosus (SLE). METHODS:The peripheral blood of SLE patients and healthy subjects were collected, and B lymphocytes were isolated. The cells were stimulated with F(ab')2; fragments of anti-μ chain antibodies [F(ab')2; anti-μ, for B cell receptor (BCR) crosslinking] or with whole immunoglobulin G (IgG) anti-μ chain antibodies (IgG anti-μ, for BCR and FcγRIIb1 co-crosslinking). The lipid rafts in the cell membrane were extracted by density-gradient ultracentrifugation. FcγRIIb1 localization, FcγRIIb1 tyrosine residue phosphorylation, and SH2-containing inositol phosphatase (SHIP) recruitment to FcγRIIb1 in the lipid rafts were detected by immunoprecipitation and Western blotting. RESULTS:After B lymphocyte stimulation with F(ab')2; anti-μ, FcγRIIb1 translocation to lipid rafts, as well as tyrosine-phosphorylated FcγRIIb1 and SHIP recruitment to FcγRIIb1 in the lipid rafts, showed no significant changes in the B lymphocytes from SLE patients compared with those in the healthy control subjects. However, after B lymphocyte stimulation with IgG anti-μ, the above indexes were significantly lower in the B lymphocytes from SLE patients than in the healthy control subjects. CONCLUSION:This study provides evidence for the decreased FcγRIIb1 translocation to lipid rafts as well as for the reduced tyrosine-phosphorylated FcγRIIb1 and SHIP recruitment to FcγRIIb1 in lipid rafts of B lymphocytes from SLE patients after stimulated with IgG anti-μ.