Mickie H. Cheng

Protein microarray analysis reveals BAFF-binding autoantibodies in systemic lupus erythematosus

Autoantibodies against cytokines, chemokines, and growth factors inhibit normal immunity and are implicated in inflammatory autoimmune disease and diseases of immune deficiency. In an effort to evaluate serum from autoimmune and immunodeficient patients for Abs against cytokines, chemokines, and growth factors in a high-throughput and unbiased manner, we constructed a multiplex protein microarray for detection of serum factor-binding Abs and used the microarray to detect autoantibody targets in SLE. We designed a nitrocellulose-surface microarray containing human cytokines, chemokines, and other circulating proteins and demonstrated that the array permitted specific detection of serum factor-binding probes. We used the arrays to detect previously described autoantibodies against cytokines in samples from individuals with autoimmune polyendocrine syndrome type 1 and chronic mycobacterial infection. Serum profiling from individuals with SLE revealed that among several targets, elevated IgG autoantibody reactivity to B cell-activating factor (BAFF) was associated with SLE compared with control samples. BAFF reactivity correlated with the severity of disease-associated features, including IFN-α-driven SLE pathology. Our results showed that serum factor protein microarrays facilitate detection of autoantibody reactivity to serum factors in human samples and that BAFF-reactive autoantibodies may be associated with an elevated inflammatory disease state within the spectrum of SLE.

COPA mutations impair ER-Golgi transport and cause hereditary autoimmune-mediated lung disease and arthritis

Unbiased genetic studies have uncovered surprising molecular mechanisms in human cellular immunity and autoimmunity. We performed whole-exome sequencing and targeted sequencing in five families with an apparent mendelian syndrome of autoimmunity characterized by high-titer autoantibodies, inflammatory arthritis and interstitial lung disease. We identified four unique deleterious variants in the COPA gene (encoding coatomer subunit α) affecting the same functional domain. Hypothesizing that mutant COPA leads to defective intracellular transport via coat protein complex I (COPI), we show that COPA variants impair binding to proteins targeted for retrograde Golgi-to-ER transport. Additionally, expression of mutant COPA results in ER stress and the upregulation of cytokines priming for a T helper type 17 (TH17) response. Patient-derived CD4+ T cells also demonstrate significant skewing toward a TH17 phenotype that is implicated in autoimmunity. Our findings uncover an unexpected molecular link between a vesicular transport protein and a syndrome of autoimmunity manifested by lung and joint disease.

T cells in the control of organ-specific autoimmunity

Immune tolerance is critical to the avoidance of unwarranted immune responses against self antigens. Multiple, non-redundant checkpoints are in place to prevent such potentially deleterious autoimmune responses while preserving immunity integral to the fight against foreign pathogens. Nevertheless, a large and growing segment of the population is developing autoimmune diseases. Deciphering cellular and molecular pathways of immune tolerance is an important goal, with the expectation that understanding these pathways will lead to new clinical advances in the treatment of these devastating diseases. The vast majority of autoimmune diseases develop as a consequence of complex mechanisms that depend on genetic, epigenetic, molecular, cellular, and environmental elements and result in alterations in many different checkpoints of tolerance and ultimately in the breakdown of immune tolerance. The manifestations of this breakdown are harmful inflammatory responses in peripheral tissues driven by innate immunity and self antigen-specific pathogenic T and B cells. T cells play a central role in the regulation and initiation of these responses. In this Review we summarize our current understanding of the mechanisms involved in these fundamental checkpoints, the pathways that are defective in autoimmune diseases, and the therapeutic strategies being developed with the goal of restoring immune tolerance.

BPIFB1 IS A LUNG-SPECIFIC AUTOANTIGEN ASSOCIATED WITH INTERSTITIAL LUNG DISEASE

Autoimmunity targeting the lung-specific antigen BPIFB1 may be important to the pathogenesis of interstitial lung disease. Seeing the Forest by Examining the Trees Sometimes looking at something too closely obscures the big picture. However, when the big picture is too big, a reductionist approach may be best. Interstitial lung disease (ILD) is a complex and heterogeneous disorder, frequently associated with autoimmune syndromes. However, due in part to this heterogeneity, it remains unclear whether autoimmunity directly contributes to ILD. Now, Shum et al. attack this question by example—connecting one form of autoimmune disease, autoimmune polyglandular syndrome type 1 (APS1), with clinical ILD. The authors screened patients with APS1 and found autoantibodies to a lung-specific protein—BPIFB1—associated with the development of ILD in APS1 patients. They then extended these findings to non-APS1–associated ILD and found that 12 to 15% of patients also had these autoantibodies. The authors then examined a potential pathogenic mechanism of these autoantibodies in a mouse model of APS1, finding that similar autoantibodies and development of ILD resulted from a defect in thymic tolerance. Indeed, autoimmune targeting of BPIFB1 could cause ILD in mice without the autoimmune defect. These results suggest not only that ILD may be an autoimmune disorder in APS1 patients but also that autoimmunity may also contribute to pathology in a broader swath of ILD patients. Interstitial lung disease (ILD) is a complex and heterogeneous disorder that is often associated with autoimmune syndromes. Despite the connection between ILD and autoimmunity, it remains unclear whether ILD can develop from an autoimmune response that specifically targets the lung parenchyma. We examined a severe form of autoimmune disease, autoimmune polyglandular syndrome type 1 (APS1), and established a strong link between an autoimmune response to the lung-specific protein BPIFB1 (bactericidal/permeability-increasing fold-containing B1) and clinical ILD. Screening of a large cohort of APS1 patients revealed autoantibodies to BPIFB1 in 9.6% of APS1 subjects overall and in 100% of APS1 subjects with ILD. Further investigation of ILD outside the APS1 disorder revealed BPIFB1 autoantibodies present in 14.6% of patients with connective tissue disease–associated ILD and in 12.0% of patients with idiopathic ILD. The animal model for APS1, Aire−/− mice, harbors autoantibodies to a similar lung antigen (BPIFB9); these autoantibodies are a marker for ILD. We found that a defect in thymic tolerance was responsible for the production of BPIFB9 autoantibodies and the development of ILD. We also found that immunoreactivity targeting BPIFB1 independent of a defect in Aire also led to ILD, consistent with our discovery of BPIFB1 autoantibodies in non-APS1 patients. Overall, our results demonstrate that autoimmunity targeting the lung-specific antigen BPIFB1 may contribute to the pathogenesis of ILD in patients with APS1 and in subsets of patients with non-APS1 ILD, demonstrating the role of lung-specific autoimmunity in the genesis of ILD.

Autoimmune Oophoritis with Multiple Molecular Targets Mitigated by Transgenic Expression of Mater

Primary ovarian insufficiency (POI) resulting from ovarian autoimmunity is a poorly understood clinical condition lacking in effective treatments. Understanding the targets of the autoimmune response and induction of ovarian-specific tolerance would allow development of focused therapies to preserve fertility in an at-risk population. MATER (maternal antigen that embryos require) is a known ovarian autoantigen targeted in autoimmune syndromes of POI. We attempt to induce ovarian-specific tolerance via transgenic expression of the MATER antigen on potentially tolerogenic antigen-presenting cells (APC), which typically present antigen via the major histocompatibility complex (MHC) class II molecule. We hypothesize that expression of MATER in a MHC class II-dependent manner on APC can mediate induction of ovarian tolerance. We utilized a well-characterized murine model of ovarian autoimmunity, whereby oophoritis develops after d 3 neonatal thymectomy (NTx). Wild-type and transgenic mice, carrying an MHC Class II-driven Mater gene (IE-Mater), were subjected to NTx and assessed for evidence of autoimmune oophoritis. After disease induction by NTx, female mice carrying the IE-Mater transgene had significant reductions in histological oophoritis (56%) and circulating ovarian autoantibodies (28%) compared with wild-type females (94% and 82%, respectively). Incidence of other autoimmunity was unaffected as assessed by antinuclear autoantibodies. Transgenic expression of MATER in APC can induce antigen-specific tolerance with a significant reduction in ovarian autoimmunity. Lack of complete disease protection suggests that other antigens may also play a role in autoimmune oophoritis. As a known autoantigen in the human APS1 (autoimmune polyglandular syndrome type 1), which is associated with POI, MATER may represent a relevant target for future diagnostic and therapeutic clinical interventions.

Insights into type 1 diabetes from the autoimmune polyendocrine syndromes.

Purpose of review Advances in human genetics and investigations in animal models of autoimmune disease have allowed insight into the basic mechanisms of immunologic tolerance. These advances allow us to understand the pathogenesis of type 1 diabetes and other autoimmune diseases as never before. Here, we discuss the tolerance mechanisms of the autoimmune polyendocrine syndromes and their relevance to type 1 diabetes. Recent findings Defects in central tolerance with alteration of self-antigen expression levels in the thymus are a potent cause of autoimmunity. Peripheral tolerance defects that alter T-cell activation and signaling also play an important role in the pathogenesis of diabetes and other associated autoimmune disorders, with multiple modest defects working in concert to produce disease. Regulation of the immune response through the action of regulatory T cells is a potent mode of tolerance induction in autoimmunity that is important in type 1 diabetes. Summary Rare syndromes of autoimmunity provide a valuable window into the breakdown of tolerance and identify multiple checkpoints that are critical for generation of autoimmunity. Understanding the application of these in type 1 diabetes will allow the development of future immunomodulatory therapies in the treatment and prevention of disease.

Mechanisms and models of immune tolerance breakdown in the ovary.

Ovarian autoimmunity is increasingly implicated in the etiology of primary ovarian insufficiency (POI), previously termed PREMATURE OVARIAN FAILURE or PREMATURE MENOPAUSE. Links to autoimmunity in human POI have long been noted due to the close association of POI with several autoimmune diseases and syndromes such as Addisons disease and Autoimmune polyglandular syndrome 1. However, diagnosis of autoimmune-mediated POI (aPOI) remains challenging because of the lack of sensitive or specific markers of disease. Autoimmunity can arise from the breakdown of immunological tolerance in several ways. How then may we discern what constitutes a relevant target and what represents a downstream phenomenon? The answer lies in the study of pathogenic mechanisms in translational models of disease. From examples in humans and mice, we see that ovarian autoimmunity likely arises from a limited number of antigens targeted in the ovary that are organ specific. These antigens may be conserved but not limited to those seen in animal models of autoimmune ovarian disease. Recent advances in these areas have begun to define the relevant antigens and mechanisms of immune tolerance breakdown in the ovary. Work in translational models continues to provide insight into mechanisms of disease pathogenesis that will allow more accurate diagnosis and, ultimately, improved interventions for women with aPOI.

Thymic tolerance as a key brake on autoimmunity

Although the thymus has long been recognized as a key organ for T cell selection, the intricate details linking these selection events to human autoimmunity have been challenging to decipher. Over the last two decades, there has been rapid progress in understanding the role of thymic tolerance mechanisms in autoimmunity through genetics. Here we review some of the recent progress in understanding key thymic tolerance processes that are critical for preventing autoimmune disease.The thymus has a critical role in the establishment of appropriately educated and self-tolerant T cells. In their Focus Review, Cheng and Anderson discuss the most recent insights into how the thymus establishes self-tolerance.

Sleepless and Diabetic

Rare variants in the melatonin receptor may explain an increased risk for type 2 diabetes.

Model Remodeling-Osteocytes Take Center Stage

Unexpectedly, bone matrix–embedded osteocytes, not osteoblasts, maintain the uncertain balance between bone formation and resorption that goes awry in osteoporosis.