The results showed that the phosphorylation of S6(Ser235/236) and T-bet expression were not dependent on proliferation and rapamycin strongly decreased the frequencies of p-S6+ and T-bet+ B cells in gated live non-proliferating B cells (online supplementary figure 4G,H)

The results showed that the phosphorylation of S6(Ser235/236) and T-bet expression were not dependent on proliferation and rapamycin strongly decreased the frequencies of p-S6+ and T-bet+ B cells in gated live non-proliferating B cells (online supplementary figure 4G,H). of patients with treatment-na?ve lupus. Gene expression profile indicated that B cell signalling and activation, lipid/saccharide metabolism and endocytosis pathways were abnormally upregulated in lupus AtMs. In addition, the mammalian target of rapamycin complex 1 (mTORC1) pathway was remarkably activated in lupus AtMs, and blocking mTORC1 signalling by rapamycin abolished the generation of T-bet+ B cells and terminal differentiation of lupus AtMs. Furthermore, lupus AtMs displayed a dysfunctional phenotype, underwent accelerated apoptosis, poorly co-stimulated T cells and produced proinflammatory cytokines. Interestingly, lupus AtMs were in a paradoxically differentiated status with markers pro and against terminal differentiation and enriched with antinucleosome reactivity. Finally, AtMs were accumulated in the kidneys of patients with lupus nephritis and associated with disease severity. Conclusions These findings demonstrated that mTORC1-overactivated lupus AtMs are abnormally differentiated with metabolic and functional dysregulations. Inhibiting mTORC1 signalling might be an attractive option to target AtMs and to improve therapeutic effectiveness in patients with lupus. Keywords: systemic lupus erythematosus, B cells, cytokines Key messages What is already known about this subject? T-bet+CD11c+ atypical memory B cells (AtMs) are greatly expanded in lupus and implicated in the pathogenesis of systemic lupus erythematosus (SLE). What does this study add? We find that the mTORC1 pathway is Hyodeoxycholic acid highly activated in lupus AtMs and plays a critical role in the generation and terminal differentiation of these cells. Importantly, inhibiting mTORC1 signalling by rapamycin blocks T-bet+ B cell generation and the terminal differentiation of AtMs. Our study also demonstrates that AtMs are aberrantly differentiated, metabolically abnormal and functionally dysregulated. In addition, the abundance of AtMs both in the blood and in the kidneys of patients with lupus nephritis reflects the disease activity, indicating that AtMs could be a novel biomarker for patients with lupus. GDF2 How might this impact on clinical practice or future developments? Targeting AtMs by inhibiting mTORC1 signalling pathway could be an attractive option to improve therapeutic effectiveness in patients with SLE. Introduction Systemic lupus erythematosus (SLE) is an autoimmune disease triggered by loss of self-tolerance and the resultant autoreactive cellular and humoral immune responses, leading to a striking heterogeneity of clinical manifestations and organ dysfunction.1 2 B cell abnormality plays a central role in the development of SLE by contributing to the overproduction of autoantibodies, cytokines and augmented presentation of autoantigens to T cells.3 Hyodeoxycholic acid 4 The B cell compartment is highly distorted in patients with active SLE. Transitional B cells and plasmablasts are greatly increased, while non-switched memory B cells are decreased in active SLE.5C7 In addition, a population of atypical memory B cells (AtMs) sharing similar phenotypes and identified as CD19hi,8 CD19hiCD21lo,5 9 CD27?IgD? 10 11 are expanded in active SLE. Increased frequency of these AtMs has been associated with high disease activity and disease-specific autoantibodies such as anti-Smith (Sm) antibody,8 10 suggesting that these cells are associated with disease development. Phenotypically similar B cells were also expanded in other autoimmune diseases like primary Sjoegrens syndrome, systemic sclerosis5 and infectious diseases like HIV infection,12 hepatitis C virus infection13 and malaria.14 Thus, an environment of chronic inflammation seems to promote the generation of these B cells. Recent studies have revealed that human AtMs specifically express transcription factor (TF) T-bet and integrin CD11c15C17 which are closely linked to a population of B cells named age-associated B cells (ABCs) in aged female mice and young lupus-prone mice.18 19 Murine ABCs are T-bet+CD11c+ and enriched with antichromatin autoantibodies which play an essential role in lupus development.16 19 Furthermore, T-bet is necessary and sufficient for the generation of murine CD11c+ ABCs20 and deletion of T-bet in B cells causes a loss of CD11c+ ABCs and the amelioration of disease in lupus-prone mice.16 21 These studies demonstrated a common pathogenic role of T-bet+CD11c+ B cells in both human lupus and murine lupus models. The Hyodeoxycholic acid identification of a population of atypical memory T-bet+CD11c+ B cells in patients with SLE raises the possibility that targeting this population may open new therapeutic opportunities for this complex disease, as the efficacies of B cell depletion therapy by targeting whole B cells in patients Hyodeoxycholic acid with SLE are highly variable.1 22 Particularly, it was reported that an expanded population of CD19hi AtMs in patients with Hyodeoxycholic acid SLE predicts a poor clinical response to rituximab treatment.8 Although several factors including Toll-like receptor (TLR) 7, interferon gamma (IFN-), interleukin (IL) 21 have been implicated in the differentiation of AtMs,19 20 23 24 no clinically targetable pathway has been identified so far. Thus, to identify the key pathway leading to their generation and to develop feasible strategies to block their development represent an urgent need in lupus B cell study. In this.