The pathogenic roles of B cells in autoimmune diseases occur through several mechanistic pathways that include autoantibodies, immune complexes, dendritic and T cell activation, cytokine synthesis, ...chemokine-mediated functions, and ectopic neolymphogenesis. Each of these pathways participate to different degrees in autoimmune diseases. The use of B cell-targeted and B cell subset-targeted therapies in humans is illuminating the mechanisms at work in a variety of human autoimmune diseases. In this review, we highlight some of these recent findings that provide insights into both murine models of autoimmunity and human autoimmune diseases.
De-ubiquitinating enzyme BAP1 is mutated in a hereditary cancer syndrome with increased risk of mesothelioma and uveal melanoma. Somatic BAP1 mutations occur in various malignancies. We show that ...mouse Bap1 gene deletion is lethal during embryogenesis, but systemic or hematopoietic-restricted deletion in adults recapitulates features of human myelodysplastic syndrome (MDS). Knockin mice expressing BAP1 with a 3xFlag tag revealed that BAP1 interacts with host cell factor—1 (HCF-1), O-linked N-acetylglucosamine transferase (OGT), and the polycomb group proteins ASXL1 and ASXL2 in vivo. OGT and HCF-1 levels were decreased by Bap1 deletion, indicating a critical role for BAP1 in stabilizing these epigenetic regulators. Human ASXL1 is mutated frequently in chronic myelomonocytic leukemia (CMML) so an ASXL/BAP1 complex may suppress CMML. A BAP1 catalytic mutation found in a MDS patient implies that BAP1 loss of function has similar consequences in mice and humans.
Lacking any discernible sequence similarity, interleukin-34 (IL-34) and colony stimulating factor 1 (CSF-1) signal through a common receptor CSF-1R on cells of mononuclear phagocyte lineage. Here, ...the crystal structure of dimeric IL-34 reveals a helical cytokine fold homologous to CSF-1, and we further show that the complex architecture of IL-34 bound to the N-terminal immunoglobulin domains of CSF-1R is similar to the CSF-1/CSF-1R assembly. However, unique conformational adaptations in the receptor domain geometry and intermolecular interface explain the cross-reactivity of CSF-1R for two such distantly related ligands. The docking adaptations of the IL-34 and CSF-1 quaternary complexes, when compared to the stem cell factor assembly, draw a common evolutionary theme for transmembrane signaling. In addition, the structure of IL-34 engaged by a Fab fragment reveals the mechanism of a neutralizing antibody that can help deconvolute IL-34 from CSF-1 biology, with implications for therapeutic intervention in diseases with myeloid pathogenic mechanisms.
► Structure of human IL-34 reveals a dimeric four-helix bundle cytokine fold ► Studies in solution confirm bivalent assembly and high affinity of IL-34 with CSF-1R ► The IL-34/CSF-1R complex structure shares a common architecture with CSF-1/CSF-1R ► CSF-1R employs distinct domain adaptations for binding to IL-34 and CSF-1
Large collections of knockout organisms facilitate the elucidation of gene functions. Here we used retroviral insertion or homologous recombination to disrupt 472 genes encoding secreted and membrane ...proteins in mice, providing a resource for studying a large fraction of this important class of drug target. The knockout mice were subjected to a systematic phenotypic screen designed to uncover alterations in embryonic development, metabolism, the immune system, the nervous system and the cardiovascular system. The majority of knockout lines exhibited altered phenotypes in at least one of these therapeutic areas. To our knowledge, a comprehensive phenotypic assessment of a large number of mouse mutants generated by a gene-specific approach has not been described previously.
Background Atopic dermatitis (AD) and psoriasis are common inflammatory diseases canonically described as involving distinct TH polarization and granulocytic infiltration. Acute AD lesions are ...associated with TH 2 and eosinophilic inflammation, whereas psoriatic lesions are associated with TH 1/TH 17 and neutrophilic inflammation. Despite intensive investigation, these pathways remain incompletely understood in vivo in human subjects. Objective Using AD and psoriatic lesional skin as exemplar TH 2 and TH 1/TH 17 diseased tissue, we sought to clarify common and unique molecular and pathophysiologic features in inflamed skin with different types of inflammatory polarization. Methods We conducted gene expression microarray analyses to identify distinct and commonly dysregulated expression in AD (based on Hanifin and Rajka criteria) and psoriatic lesions. We defined gene sets (GSs) as comprising genes encoding cytokines, chemokines, and growth factors that were uniquely or jointly dysregulated in patients with AD and those with psoriasis and calculated aggregate GS expression scores for lesional skin of patients with these dermatoses and healthy control skin. Results The atopic dermatitis gene set (AD-GS) score correlated with systemic and local measures of allergic inflammation, including serum IgE levels, blood eosinophil counts, and tissue eosinophil counts. Unexpectedly, genes encoding neutrophil chemoattractants among the common GS were highly expressed in AD lesional skin. Hematoxylin and eosin and immunohistochemical analyses showed the numbers of neutrophils in AD lesional skin were comparable with those in psoriatic lesional skin, and both were correlated with the extent of expression of neutrophil chemoattractant genes. Conclusion These data are evidence that neutrophilic inflammation is a feature of lesional AD pathology comorbid with allergic inflammation.
Objective
To determine whether a combination of B cell depletion and BAFF blockade is more effective than monotherapy in treating models of spontaneous or accelerated systemic lupus erythematosus ...(SLE) in (NZB × NZW)F1 mice.
Methods
Clinical parameters such as disease progression–free survival, proteinuria, and renal injury were assessed in models of spontaneous, interferon‐α (IFNα)–accelerated, or pristane‐accelerated lupus in (NZB × NZW)F1 mice. Treatment arms included anti‐CD20 (B cell depletion), B lymphocyte stimulator receptor 3 fusion protein (BR‐3‐Fc) (BAFF blockade), the combination of anti‐CD20 and BR‐3‐Fc, isotype control, or cyclophosphamide. In models of spontaneous, IFNα‐accelerated, or pristane‐accelerated lupus, mice were treated for 24 weeks, 8 weeks, or 12 weeks, respectively. Peripheral and resident B cell subsets and various autoantibodies were examined.
Results
Compared to B cell depletion or BAFF blockade alone, combined therapy significantly improved disease manifestations in all 3 lupus models. In addition, marginal zone B cells, plasmablasts, and circulating and tissue plasma cells were decreased more effectively. Dual B cell immunotherapy also reduced multiple classes of pathogenic autoantibodies, consistent with its observed effectiveness in reducing immune complex–mediated renal injury.
Conclusion
Dual immunotherapy via B cell depletion and BAFF blockade is more efficacious than single agent immunotherapy in murine SLE models, and this combination treatment is predicted to be an effective strategy for immunotherapy in human SLE.
Lysosomal storage diseases (LSDs) are a group of heterogeneous disorders caused by defects in lysosomal enzymes or transporters, resulting in accumulation of undegraded macromolecules or metabolites. ...Macrophage numbers are expanded in several LSDs, leading to histiocytosis of unknown pathophysiology. Here, we found that mice lacking the equilibrative nucleoside transporter 3 (ENT3) developed a spontaneous and progressive macrophage-dominated histiocytosis. In the absence of ENT3, defective apoptotic cell clearance led to lysosomal nucleoside buildup, elevated intralysosomal pH, and altered macrophage function. The macrophage accumulation was partly due to increased macrophage colony-stimulating factor and receptor expression and signaling secondary to the lysosomal defects. These studies suggest a cellular and molecular basis for the development of histiocytosis in several human syndromes associated with ENT3 mutations and potentially other LSDs.
Joint and skeletal development is highly regulated by extracellular matrix (ECM) proteoglycans, of which chondroitin sulfate proteoglycans (CSPGs) are a major class. Despite the requirement of joint ...CSPGs for skeletal flexibility and structure, relatively little is understood regarding their role in establishing joint positioning or in modulating signaling and cell behavior during joint formation. Chondroitin sulfate synthase 1 (Chsy1) is one of a family of enzymes that catalyze the extension of chondroitin and dermatan sulfate glycosaminoglycans. Recently, human syndromic brachydactylies have been described to have loss-of-function mutations at the CHSY1 locus. In concordance with these observations, we demonstrate that mice lacking Chsy1, though viable, display chondrodysplasia and decreased bone density. Notably, Chsy1−/− mice show a profound limb patterning defect in which orthogonally shifted ectopic joints form in the distal digits. Associated with the digit-patterning defect is a shift in cell orientation and an imbalance in chondroitin sulfation. Our results place Chsy1 as an essential regulator of joint patterning and provide a mouse model of human brachydactylies caused by mutations in CHSY1.
► Chsy1 modulates chondrocyte development/maintenance throughout the skeleton. ► Chsy1 influences cell orientation in developing autopods. ► CS chains in Chsy1 null mice display a disruption in chondroitin sulfation balance. ► Hh and Gdf5 signaling is altered in Chsy1 null cells and tissues.
B cell immunotherapy has emerged as a mainstay in the treatment of lymphomas and autoimmune diseases. Although the microenvironment has recently been demonstrated to play critical roles in B cell ...homeostasis, its contribution to immunotherapy is unknown. To analyze the in vivo factors that regulate mechanisms involved in B cell immunotherapy, we used a murine model for human CD20 (hCD20) expression in which treatment of hCD20(+) mice with anti-hCD20 mAbs mimics B cell depletion observed in humans. We demonstrate in this study that factors derived from the microenvironment, including signals from the B cell-activating factor belonging to the TNF family/BLyS survival factor, integrin-regulated homeostasis, and circulatory dynamics of B cells define distinct in vivo mechanism(s) and sensitivities of cells in anti-hCD20 mAb-directed therapies. These findings provide new insights into the mechanisms of immunotherapy and define new opportunities in the treatment of cancers and autoimmune diseases.
Using immunoglobulin heavy chain transgenic mice, we show that B cell clones reaching the long-lived pool are heterogeneous: some are enriched in the CD21(high) compartment (mostly marginal zone MZ), ...others reside primarily in the follicles (FO). Altering the composition of the B cell receptor through N region additions decreases the rate of clonal production and the MZ enrichment. This process can be recapitulated by purified CD21(low) B cells and is due to a preferential clonal survival that requires a functional btk tyrosine kinase. We also show that generation of the MZ population is dependent on CD19. These findings suggest that the MZ B cell repertoire is positively selected and have functional implications for antigenic responses effected by B cells from this microenvironment.
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