B cells present lipid antigens to CD1d-restricted invariant natural killer T (iNKT) cells to maintain autoimmune tolerance, and this process is disrupted in systemic lupus erythematosus (SLE). Inflammation may inhibit CD1d expression to exacerbate the pathology of lupus. However, how inflammation regulates CD1d expression on B cells is unclear in SLE.In the present study, we showed that the surface expression of CD1d on B cells from SLE mice was decreased and that stimulation of inflammatory responses through TLR9 decreased the membrane and total CD1d levels of CD1d on B cells. Moreover, inflammation-related microRNA-155 (miR-155) negatively correlated with the expression of CD1d in B cells. miR-155 directly targeted the 3 -untranslated region (3 -UTR) of CD1d upon TLR9 activation in both humans and mice. The inhibitory effects of miR-155 on CD1d expression in B cells impaired their antigen-presenting capacity to iNKT cells. In addition, Ets-1, a susceptibility gene of SLE, also directly regulated the expression of the CD1d gene at the transcriptional level. These findings provide new insight into the mechanism underlying decreased CD1d expression on B cells in SLE, suggesting that inhibition of inflammation may increase CD1d expression in B cells to ameliorate SLE via modulating iNKT cells.Keywords: B cells r CD1d r Ets-1 r miR-155 r SLE Additional supporting information may be found in the online version of this article at the publisher's web-site
IntroductionSystemic lupus erythematosus (SLE) is a complex and chronic autoimmune disease with an unclear etiology [1]. B cells play a central role in the pathogenesis of SLE [2], and patients with SLE exhibit abnormal B-cell activation and increased sensitivity and proliferation of B cells [3]. Moreover, the Correspondence: Dr. Yayi Hou e-mail: yayihou@nju.edu.cn clinical success of B-cell depletion therapy further proves the important role of B cells in SLE pathogenesis [4,5]. B cells not only produce antibodies and release cytokines and chemokines but also present both peptide and lipid antigens [6].CD1 family molecules are nonclassical MHC proteins related to the class I MHC proteins and are involved in the presentation of lipid antigens to T cells. Several studies have suggested that CD1d may play an immunoregulatory role in the development of lupus, and CD1d deficiency exacerbates lupus nephritis in the pristineinduced model [7] and inflammatory dermatitis in MRL-lpr/lpr C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2015. 45: 1934-1945 Cellular immune response 1935 mice [8]. Importantly, endogenous DNA stimulates inflammatory responses through TLR9 and exacerbates lupus disease pathology [9,10]. Viral infection could downregulate the expression of CD1d in APCs, such as B cells [11,12], DCs, and macrophages [13]. A number of exogenous viruses, especially Epstein-Barr virus (EBV) [14,15], also have been linked to the pathogenesis of SLE [16]. Our previous studies have indicated that ligands for both TLR9 and TLR7 lead to B...