Winslow, Gary; Levack, Russell (2020)
      CD11c+ T-bet+ B cells serve crucial roles in both protective immunity and autoimmunity.However, the ontogeny of these cells remains unclear, and strategies to target them in vivo have yet to be identified. Here, we demonstrate that developing CD11c+ T-bet+ B cells received help in the form of IL-21, IFN-γ, and CD40L from a population ofT follicular helper 1(TFH1)cells outside of formal germinal centers (GC). These TFH1cells provided help to developing CD11c+ T-bet+ B cells in two distinct phases: IFN-gwas provided early following infection, and CD40L was provided later. Unlike the TFH1cells, CD11c+ T-bet+ B cells required the GC-associated transcription factor Bcl-6 for their development, but not T-bet. While the CD11c+ B cells that arose in the absence of T-bet appeared nearly identical to their T-bet-competent counterparts,they did not switch to IgG2c. These data support a model where, in the absence of formal GCs, TFH1cells provide GC-like help to developing CD11c+ T-bet+ B cells and while T-bet is not required for the development of these T-bet+ B cells,it is required for appropriate class-switch recombination (CSR). Our work also demonstrates that mature CD11c+ T-bet+ B cells, which arise in both immunity and autoimmunity,wereeliminated following treatment with the adenosine 2a receptor (A2aR) agonist CGS-21680. Depletion of these CD11c+ T-bet+ B cells occurred in a B cell-intrinsic manner and was corelated with improved disease outcome in a mouse model of lupus. Preliminary data indicated that human CD11c+ B cells expressed the A2aR,and these cells were depleted following CGS-21680 treatment in vitro, suggesting that A2aR-agonistadministrationmay also be effective in the treatment of human autoimmune diseaseswhere CD11c+ Bcell play a role. Overall, this work provides novel insight into the development of T-bet+ B cells and identifies the first pharmacological approach to target these cells in vivo.
    • Metabolic Control of Autoimmunity in the Liver

      Perl, Andras; Oaks, Zachary (2016)
      Autophagy,literally meaning “self-eating,” is an integral part of cellularturnover of damaged organelles and proteins.This process is inextricably linked to mitochondrial function and turnover. Mitochondria can be degraded viaautophagy, known as mitophagy, as well as donate lipid membraneto generate autophagosomes fordigestingother organelles and proteins. On a larger scale, autophagy is essential for organ homeostasis. In the liver, autophagy ensures the turnover of damaged mitochondria that may otherwise increase oxidative stress which modifies DNA, proteins, and lipids resulting in the production of autoantigens or neoplasia. We investigated the role of autophagy and mitochondrial dysfunction prior to disease onset in mouse models of systemic lupus erythematosus (SLE). Patients and mice with SLE exhibit overexpression of transaldolase (TAL) and show predisposition to anti-phospholipid antibody production and associated liver diseases, including hepatocellular carcinoma. Wediscovered deficient mitophagy in the liver of lupus-prone mice prior to disease onset. Furthermore, these mice had increased mitochondrial respirationwith concomitant inner membrane hyperpolarization. These changes were coupled to overexpression of Rab4A, which depletes Drp1and thus inhibitsmitophagy.In addition,activation of complex I of the mechanistic target of rapamycin (mTORC1)was noted along with enhanced production of autoantibodies against mitochondrial phospholipids in lupus-prone mice. These changes were reversed by blockade of mTORC1 by rapamycin treatment in vivo. We then examined the role of TAL, a key enzyme of the pentose phosphate pathway (PPP) in mitochondrial dysfunction and oxidative stress. TAL-deficientmice showedincreased mitochondrial electron transport chain (ETC) activity and mTORC1 activation andreduced autophagy.Since inactivation of TAL caused oxidative stress via depletion of NADPH, we tested the hypothesis that aldose reductase(AR), a NADPH dependent enzymecan correct this metabolic defect without reversing the accumulation of TAL-specific substrates, sedoheptulose 7-phosphate and erythrose 4-phosphate. Moreover, deletion of AR reversed mTORC1 activation without affecting enhanced mitochondrial ETC activity or diminished autophagy. On a more global scale, predisposition to neoplasia and acetaminophen-induced liver failurewere reversed, while anti-phospholipid autoantibody production and liver fibrosis persisted in TAL/AR double-knockout mice indicatingthat the PPPmay act as a metabolic rheostat of organ-specific disease pathogenesis.
    • Metabolic Control of Autoimmunity Through Autophagy

      Choudhary, Gourav (2019)
      Metabolism plays a key role in immune cell activation and differentiation. Immune cell activation depending on their biosynthetic and bioenergetic needs leads to profound metabolic reprograming. Proinflammatory subsets of immune system cells such as effector T cells show dependency on glycolysis, whereas, regulatory T cells rely on oxidative phosphorylation. Under metabolic stress, immune cells utilize autophagy to overcome nutrient scarcity, an alternate method of recycling amino acids and other metabolic precursors. Limitation of nutrients such as amino acids activates mechanistic target of rapamycin (mTOR) in the immune cells. mTOR acts as a metabolic mediator, associated with mitochondria and metabolic needs of the immune cells. Homeostasis between mTOR activation and autophagy decides the fate and functionality of specific immune cells. The activation of mTOR is widely acknowledged in the pathogenesis of SLE, whereas, autophagy has been linked with antigen processing, presentation, and immunoregulation. In this study, we focused on Rab4A, an endosomal GTPase and Transaldolase, a rate limiting enzyme of the pentose phosphate pathway (PPP). Rab4A is over expressed in SLE T cells and facilitates lysosomal degradation of CD4 and CD3. Transaldolase is also overexpressed in T cells from SLE patients and SLE prone mice. First, we examined the role of Rab4A in a pristane-induced mouse model of SLE. Since Rab4A protects from pristane-induced alveolar lung hemorrhage, we tested the hypothesis that Rab4A will also protect from pristane-induced lupus nephritis. We found that overexpression of a constitutively active form of Rab4A limits antinuclear antibody production. Further, we found that Rab4A protects from pristane-induced renal injury by restricting immune complex depositions in the kidney. In additions, we found that Rab4A abrogates kidney-infiltration by lymphocytes and protects from podocyte injury. Furthermore, Rab4A facilitates the lysosomal mediated activation of mTOR. Possibly, the Rab4A mediated activation of mTOR in regulatory T cells leads to suppression of pristane-induced pro-inflammation signaling. In the second part, we investigated if aldose reductase (AR) deficiency can protect from Transaldolase mediated pathogenesis of liver disease. We found a coordinated regulation between AR and TAL, leading to the disease progression.