Leptin dysregulated immune responses of B cells in patients with systemic lupus erythematosus / 中华风湿病学杂志

ABSTRACT

Objective:To explore the effect of leptin on B cells in patients with systemic lupus erythematosus (SLE).Methods:Peripheral blood mononuclear cells (PBMCs) were isolated from SLE patients, and then CD19 + B cells were purified with magnetic bead sorting method. PBMCs or purified B cells were cultured with recombinant leptin at 0, 100, 250 ng/ml for 3 or 5 days. The frequencies of plasma cells, follicular helper T (Tfh) cells and peripheral helper T (Tph) cells, as well as activation markers (CD80, CD86) and leptin receptor and the proliferation of B cells were determined with flow cytometry. The concentrations of antibodies and cytokines were examined with enzyme-linked immunosorbnent assay (ELISA). Data were analyzed with t test and analysis of variance (ANOVA). Results:Increased levels of leptin were positively correlated with systematic lupus erythematosus disease activity index (SLEDAI) and the frequency of plasma cells in SLE patients. Leptin receptor could be detected on SLE B cells, and recombinant leptin elevated the levels of its receptor on CD19 + B cells [(7.8±1.3)% vs (6.1±0.9)%, t=3.36, P=0.006]. Leptin enhanced the expression of CD80 [(21±4)% vs (19±4)%, t=2.84, P=0.004] and CD86 [(22±4)% vs (19±4)%, t=4.92, P=0.004] on SLE B cells in vitro. It also promoted B cells to differentiate into plasma cells [(7.6±1.5)% vs (5.2±1.3)%, t=6.42, P=0.025]. There was no statistical significant difference of the effect of leptin on B cell proliferation. Leptin also increased the levels of antibodies [IgG (62±3) ng/ml vs (45±4) ng/ml, t=7.75, P<0.001; IgM (112±24) ng/ml vs (56±18) ng/ml, t=5.38, P<0.001] and inflammatory cytokines [IL-6 (24±5) pg/ml vs (20±5) pg/ml, t=4.09, P=0.002; TNF-α (19.1±3.8) pg/ml vs (14.1±2.9) pg/ml, t=3.38, P=0.006; IL-10 (24±5) pg/ml vs (20±5) pg/ml, t=4.09, P=0.002] secreted by B cells. In addition, leptin significantly upregulated the frequencies of Tfh cells[(2.82±0.49)% vs (1.28±0.20)%, t=4.56, P=0.001] and Tph cells [(4.5±0.5)% vs (3.4±0.4)%, t=3.88, P=0.003]. Conclusion:Leptin could directly promote the activation, differentiation and secretory capacity of B cells by binding to its receptor, and also modulate B cell responses indirectly via enhancement of Tfh and Tph cells, which may be involved in the pathogenesis of SLE.