Thomas A. Packard

HIF1A Reduces Acute Lung Injury by Optimizing Carbohydrate Metabolism in the Alveolar Epithelium

A study of acute lung injury reveals the involvement of transcription factor HIF1A in lung protection, where normoxic HIF1A stabilization functions to control alveolar epithelial glucose metabolism.

B cell depletion therapy exacerbates murine primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is considered a model autoimmune disease due to the clinical homogeneity of patients and the classic hallmark of antimitochondrial antibodies (AMAs). Indeed, the presence of AMAs represents the most highly directed and specific autoantibody in autoimmune diseases. However, the contribution of B cells to the pathogenesis of PBC is unclear. Therefore, although AMAs appear to interact with the biliary cell apotope and contribute to biliary pathology, there is no correlation of disease severity and titer of AMAs. The recent development of well‐characterized monoclonal antibodies specific for the B cell populations, anti‐CD20 and anti‐CD79, and the development of a well‐defined xenobiotic‐induced model of autoimmune cholangitis prompted us to use these reagents and the model to address the contribution of B cells in the pathogenesis of murine PBC. Prior to the induction of autoimmune cholangitis, mice were treated with either anti‐CD20, anti‐CD79, or isotype‐matched control monoclonal antibody and followed for B cell development, the appearance of AMAs, liver pathology, and cytokine production. Results of the studies reported herein show that the in vivo depletion of B cells using either anti‐CD20 or anti‐CD79 led to the development of a more severe form of cholangitis than observed in control mice, which is in contrast with results from several other autoimmune models that have documented an important therapeutic role of B cell–specific depletion. Anti‐CD20/CD79–treated mice had increased liver T cell infiltrates and higher levels of proinflammatory cytokines. Conclusion: Our results reflect a novel disease‐protective role of B cells in PBC and suggest that B cell depletion therapy in humans with PBC should be approached with caution (HEPATOLOGY 2011:53:527‐535)

B lymphocyte antigen receptor signaling: initiation, amplification, and regulation.

B lymphocytes and their differentiated daughters are charged with responding to the myriad pathogens in our environment and production of protective antibodies. A sample of the protective antibody produced by each clone is utilized as a component of the cell’s antigen receptor (BCR). Transmembrane signals generated upon antigen binding to this receptor provide the primary directive for the cell’s subsequent response. In this report, we discuss recent progress and current controversy regarding B cell receptor signal initiation, transduction and regulation.

COPD is associated with production of autoantibodies to a broad spectrum of self-antigens, correlative with disease phenotype

The role of autoimmune pathology in development and progression of chronic obstructive pulmonary disease (COPD) is becoming increasingly appreciated. In this study, we identified serum autoantibody reactivities associated with chronic bronchitis or emphysema, as well as systemic autoimmunity and associated lung disease. Using autoantigen array analysis, we demonstrated that COPD patients produce autoantibodies reactive to a broad spectrum of self-antigens. Further, the level and reactivities of these antibodies, or autoantibody profile, correlated with disease phenotype. Patients with emphysema produced autoantibodies of higher titer and reactive to an increased number of array antigens. Strikingly, the autoantibody reactivities observed in emphysema were increased over those detected in rheumatoid arthritis patients, and included similar reactivities to those associated with lupus. These findings raise the possibility that autoantibody profiles may be used to determine COPD risk, as well as provide a diagnostic and prognostic tool. They shed light on the heterogeneity of autoantibody reactivities associated with COPD phenotype and could be of use in the personalization of medical treatment, including determining and monitoring therapeutic interventions.

Loss of Anergic B Cells in Prediabetic and New-Onset Type 1 Diabetic Patients

Although dogma predicts that under normal circumstances, potentially offensive autoreactive cells are silenced by mechanisms of immune tolerance, islet antigen–reactive B lymphocytes are known to play a crucial role in the development of autoimmunity in type 1 diabetes (T1D). Thus, participation of these cells in T1D may reflect escape from silencing mechanisms. Consistent with this concept, we found that in healthy subjects, high-affinity insulin-binding B cells occur exclusively in the anergic naive IgD+, IgM− B-cell (BND) compartment. Antigen receptors expressed by these cells are polyreactive and have N-region additions, Vh usage, and charged complementarity-determining region 3 consistent with autoreactivity. Consistent with a potential early role in autoimmunity, these high-affinity insulin-binding B cells are absent from the anergic compartment of some first-degree relatives and all prediabetic and new-onset (<1 year) T1D patients tested, but return to normal levels in individuals diabetic for >1 year. Interestingly, these changes were correlated by transient loss of the entire BND compartment. These findings suggest that environmental events such as infection or injury may, by disrupting B-cell anergy, dispose individuals toward autoimmunity, the precise nature of which is specified by genetic risk factors, such as HLA alleles.

STING/MPYS Mediates Host Defense against Listeria monocytogenes Infection by Regulating Ly6C hi Monocyte Migration

MPYS (also known as STING, MITA, and TMEM173) is a type I IFN stimulator that is essential for host defense against DNA virus infection and appears important in defense against certain bacteria. The in vivo significance and mechanisms by which MPYS mediates host defense against nonviral pathogens are unknown. Using an MPYS-deficient mouse (Tmem173), we determined that, distinct from the IFNAR−/− mice, MPYS deficiency leads to increased bacterial burden in the liver upon Listeria monocytogenes infection. The increase was correlated with the diminished MCP-1 and MCP-3 chemokine production and decreased blood and liver Ly6Chi monocyte frequency. We further demonstrate that MPYS-deficient Ly6Chi monocytes are intrinsically defective in migration to the liver. Lastly, adoptive transfer of wild-type Ly6Chi monocyte into MPYS-deficient mice decreases their liver bacterial burden. Our findings reveal a novel in vivo function of MPYS that is distinct from its role in activating type I IFN production.

Neutrophil transfer of miR-223 to lung epithelial cells dampens acute lung injury in mice

Intercellular transfer of miR-223 from neutrophils to alveolar epithelial cells reduces lung inflammation in a mouse model of ventilator-induced lung injury or pulmonary bacterial infection. Starting an intercellular conversation In a new study, Neudecker et al. show that transfer of microRNA-223 (miR-223) from neutrophils to lung alveoli helps to dampen lung inflammation and promotes the resolution of ventilator-induced lung injury in mice. The authors suggest that neutrophils secrete microRNAs in microvesicles that are then taken up by alveolar epithelial cells. They show that miR-223–deficient mice are prone to lung injury, whereas overexpression of miR-223 is protective. Intercellular transfer of microRNAs can mediate communication between critical effector cells. We hypothesized that transfer of neutrophil-derived microRNAs to pulmonary epithelial cells could alter mucosal gene expression during acute lung injury. Pulmonary-epithelial microRNA profiling during coculture of alveolar epithelial cells with polymorphonuclear neutrophils (PMNs) revealed a selective increase in lung epithelial cell expression of microRNA-223 (miR-223). Analysis of PMN-derived supernatants showed activation-dependent release of miR-223 and subsequent transfer to alveolar epithelial cells during coculture in vitro or after ventilator-induced acute lung injury in mice. Genetic studies indicated that miR-223 deficiency was associated with severe lung inflammation, whereas pulmonary overexpression of miR-223 in mice resulted in protection during acute lung injury induced by mechanical ventilation or by infection with Staphylococcus aureus. Studies of putative miR-223 gene targets implicated repression of poly(adenosine diphosphate–ribose) polymerase–1 (PARP-1) in the miR-223–dependent attenuation of lung inflammation. Together, these findings suggest that intercellular transfer of miR-223 from neutrophils to pulmonary epithelial cells may dampen acute lung injury through repression of PARP-1.

Detection and Enrichment of Rare Antigen-specific B Cells for Analysis of Phenotype and Function

B cells reactive with a specific antigen usually occur at a frequency of <0.05% of lymphocytes. For decades researchers have sought methods to isolate and enrich these rare cells for studies of their phenotype and biology. Approaches are inevitably based on the principle that B cells recognize native antigen by virtue of cell surface receptors that are representative in specificity of antibodies that will eventually be secreted by their differentiated daughters. Perhaps the most obvious approach to the problem involves use of fluorochrome-conjugated antigens in conjunction with fluorescence-activated cell sorting (FACS). However, the utility of these methods is limited by cell frequency and the achievable rate of analysis and isolation by electronic sorting. A novel method to enrich rare antigen-specific B cells using magnetic nanoparticles that results in high yield enrichment of antigen-reactive B cells from large starting cell populations is described. This method enables improved monitoring of the phenotype and biology of antigen reactive cells before and following in vivo antigen encounter, such as after immunization or during development of autoimmunity.

B Cell Receptor Affinity for Insulin Dictates Autoantigen Acquisition and B Cell Functionality in Autoimmune Diabetes

B cells have been strongly implicated in the development of human type 1 diabetes and are required for disease in the NOD mouse model. These functions are dependent on B cell antigen receptor (BCR) specificity and expression of MHC, implicating linked autoantigen recognition and presentation to effector T cells. BCR-antigen affinity requirements for participation in disease are unclear. We hypothesized that BCR affinity for the autoantigen insulin differentially affects lymphocyte functionality, including tolerance modality and the ability to acquire and become activated in the diabetogenic environment. Using combined transgenic and retrogenic heavy and light chain to create multiple insulin-binding BCRs, we demonstrate that affinity for insulin is a critical determinant of the function of these autoreactive cells. We show that both BCR affinity for insulin and genetic background affect tolerance induction in immature B cells. We also find new evidence that may explain the enigmatic ability of B cells expressing 125 anti-insulin BCR to support development of TID in NOD mice despite a reported affinity beneath requirements for binding insulin at in vivo concentrations. We report that when expressed as an antigen receptor the affinity of 125 is much higher than determined by measurements of the soluble form. Finally, we show that in vivo acquisition of insulin requires both sufficient BCR affinity and permissive host/tissue environment. We propose that a confluence of BCR affinity, pancreas environment, and B cell tolerance-regulating genes in the NOD animal allows acquisition of insulin and autoimmunity.

Silencing of high-affinity insulin-reactive B lymphocytes by anergy and impact of the NOD genetic background in mice

Aims/hypothesisPrevious studies have demonstrated that high-affinity insulin-binding B cells (IBCs) silenced by anergy in healthy humans lose their anergy in islet autoantibody-positive individuals with recent-onset type 1 diabetes, and in autoantibody-negative first-degree relatives carrying certain risk alleles. Here we explore the hypothesis that IBCs are found in the immune periphery of disease-resistant C57BL/6-H2g7 mice, where, as in healthy humans, they are anergic, but that in disease-prone genetic backgrounds (NOD) they become activated and migrate to the pancreas and pancreatic lymph nodes, where they participate in the development of type 1 diabetes.MethodsWe compared the status of high-affinity IBCs in disease-resistant VH125.C57BL/6-H2g7 and disease-prone VH125.NOD mice.ResultsConsistent with findings in healthy humans, high-affinity IBCs reach the periphery in disease-resistant mice and are anergic, as indicated by a reduced expression of membrane IgM, unresponsiveness to antigen and failure to become activated or accumulate in the pancreatic lymph nodes or pancreas. In NOD mice, high-affinity IBCs reach the periphery early in life and increase in number prior to the onset of hyperglycaemia. These cells are not anergic; they become activated, produce autoantibodies and accumulate in the pancreas and pancreatic lymph nodes prior to disease development.Conclusions/interpretationThese findings are consistent with genetic determination of the escape of high-affinity IBCs from anergy and their early contribution to the development of type 1 diabetes.