Increased Serum Levels of Soluble B7-H4 in Patients with Systemic Lupus Erythematosus

Members of B7 family are reported to regulate lymphocytes activation, transmit both costimulatory and co-inhibitory signals, control T cell-mediated immune responses and tolerance. Among which B7-H4 is reported to regulate the immune response negatively. To investigate the plasma concentration of soluble B7-H4 (sB7-H4) and its clinical significance in systemic lupus erythematosus (SLE). Fifty-six SLE patients with or without active SLE (ASLE) and 29 age- and gender-matched healthy volunteers were recruited. Plasma concentration of sB7-H4 was measured using sandwich ELISA kits. Compared with healthy subjects, the concentration of sB7-H4 was significantly higher in patients with SLE (p=0.006). Plasma sB7-H4 concentration in patients with lupus nephritis (LN) were also significantly higher than healthy subjects (p=0.008), but no difference was found between LN and SLE patients without LN (non-LN). Additionally, the sB7-H4 concentration in patients was negatively correlated with the SLE disease activity index score (SLEDAI) (r=-0.3055, p=0.022). Compared with inactive disease, the concentration of sB7-H4 in ASLE patients was significantly lower (p=0.002). There were statistical significances between the positive and negative groups with decreased leukocytes or thrombocytes (p=0.012; p=0.033; respectively), but no statistically significant difference was found in other positive and negative serum laboratory indicators. The increased level of sB7-H4 in patients suggests that this pathway might be involved in the pathogenesis of SLE. However, the exact mechanism or physiological role of sB7-H4 in SLE pathogenesis remains to be investigated.