The decreased frequency of SIGIRR-positive CD4+ T cells in peripheral blood of patients with SLE and its correlation with disease activity.

Recently, many studies have shown that Single immunoglobulin interleukin-1 receptor related protein (SIGIRR), a member of the IL-1R family acting as a negative regulator of TLR/IL-1R signaling, affects autoimmune responses in animal model of systemic lupus erythematosus (SLE). However, the role of SIGIRR in the pathogenesis of human SLE has not been widely explored. In this study, we analyzed the frequency of SIGIRR-positive CD4+ T cells in peripheral blood mononuclear cells (PBMCs) of SLE patients and its correlation with disease activity as well as the clinical data. Circulating SIGIRR-positive CD4+ T cells were quantified in 51 SLE patients and 38 healthy controls by using flow cytometer. Results showed that the percentages of SIGIRR-positive CD4+ T cells were decreased in the PBMCs of SLE patients compared with healthy controls (Z = -5.49, P < 0.001). The frequency of SIGIRR-positive CD4 + T cells were also significantly decreased in SLE patients with nephritis than those without nephritis (Z = -3.71, P < 0.001). In addition, there was significant correlation between the percentages of SIGIRR-positive CD4+ T cells and SLEDAI score (r s = -0.74, P < 0.001), 24-hour urine protein (r s = -0.62, P < 0.001), Scr (r s = -0.65, P < 0.001), ESR (r s = -0.60, P < 0.001), C3 (r s = 0.53, P < 0.001) as well as C4 (r s = 0.52, P < 0.001). However, there was no correlation between the proportion of SIGIRR-positive CD4+ T cells and glucocorticoid dose (P = 0.59). In summary, decreased numbers of SIGIRR-positive CD4+ T cells in SLE patients and its correlation with SLEDAI score as well as the clinical data suggest that SIGIRR may be involved in the pathogenesis of SLE.