Loss of Bcl-6-Expressing T Follicular Helper Cells and Germinal Centers in COVID-19.

Humoral responses in coronavirus disease 2019 (COVID-19) are often of limited durability, as seen with other human coronavirus epidemics. To address the underlying etiology, we examined post mortem thoracic lymph nodes and spleens in acute SARS-CoV-2 infection and observed the absence of germinal centers and a striking reduction in Bcl-6+ germinal center B cells but preservation of AID+ B cells. Absence of germinal centers correlated with an early specific block in Bcl-6+ TFH cell differentiation together with an increase in T-bet+ TH1 cells and aberrant extra-follicular TNF-α accumulation. Parallel peripheral blood studies revealed loss of transitional and follicular B cells in severe disease and accumulation of SARS-CoV-2-specific "disease-related" B cell populations. These data identify defective Bcl-6+ TFH cell generation and dysregulated humoral immune induction early in COVID-19 disease, providing a mechanistic explanation for the limited durability of antibody responses in coronavirus infections, and suggest that achieving herd immunity through natural infection may be difficult.

CD4+CTLs in Fibrosing Mediastinitis Linked to Histoplasma capsulatum.

Although fibrotic disorders are frequently assumed to be linked to TH2 cells, quantitative tissue interrogation studies have rarely been performed to establish this link and certainly many fibrotic diseases do not fall within the type 2/allergic disease spectrum. We have previously linked two human autoimmune fibrotic diseases, IgG4-related disease and systemic sclerosis, to the clonal expansion and lesional accumulation of CD4+CTLs. In both these diseases TH2 cell accumulation was found to be sparse. Fibrosing mediastinitis linked to Histoplasma capsulatum infection histologically resembles IgG4-related disease in terms of the inflammatory infiltrate and fibrosis, and it provides an example of a fibrotic disease of infectious origin in which the potentially profibrotic T cells may be induced and reactivated by fungal Ags. We show in this study that, in this human disease, CD4+CTLs accumulate in the blood, are clonally expanded, infiltrate into disease lesions, and can be reactivated in vitro by H. capsulatum Ags. TH2 cells are relatively sparse at lesional sites. These studies support a general role for CD4+CTLs in inflammatory fibrosis and suggest that fibrosing mediastinitis is an Ag-driven disease that may provide important mechanistic insights into the pathogenesis of idiopathic fibrotic diseases.

Temporal changes in T cell subsets and expansion of cytotoxic CD4+ T cells in the lungs in severe COVID-19.

Many studies have been performed in severe COVID-19 on immune cells in the circulation and on cells obtained by bronchoalveolar lavage. Most studies have tended to provide relative information rather than a quantitative view, and it is a combination of approaches by various groups that is helping the field build a picture of the mechanisms that drive severe lung disease. Approaches employed to date have not revealed information on lung parenchymal T cell subsets in severe COVID-19. Therefore, we sought to examine early and late T cell subset alterations in the lungs and draining lymph nodes in severe COVID-19 using a rapid autopsy protocol and quantitative imaging approaches. Here, we have established that cytotoxic CD4+ T cells (CD4 + CTLs) increase in the lungs, draining lymph nodes and blood as COVID-19 progresses. CD4 + CTLs are prominently expanded in the lung parenchyma in severe COVID-19. In contrast CD8+ T cells are not prominent, exhibit increased PD-1 expression, and no obvious increase is seen in the number of Granzyme B+ CD8+ T cells in the lung parenchyma in severe COVID-19. Based on quantitative evidence for re-activation in the lung milieu, CD4 + CTLs may be as likely to drive viral clearance as CD8+ T cells and may also be contributors to lung inflammation and eventually to fibrosis in severe COVID-19.

DOCK2 Sets the Threshold for Entry into the Virtual Memory CD8+ T Cell Compartment by Negatively Regulating Tonic TCR Triggering.

The control of cytoskeletal dynamics by dedicator of cytokinesis 2 (DOCK2), a hematopoietic cell-specific actin effector protein, has been implicated in TCR signaling and T cell migration. Biallelic mutations in Dock2 have been identified in patients with a recessive form of combined immunodeficiency with defects in T, B, and NK cell activation. Surprisingly, we show in this study that certain immune functions of CD8+ T cells are enhanced in the absence of DOCK2. Dock2-deficient mice have a pronounced expansion of their memory T cell compartment. Bone marrow chimera and adoptive transfer studies indicate that these memory T cells develop in a cell-intrinsic manner following thymic egress. Transcriptional profiling, TCR repertoire analyses, and cell surface marker expression indicate that Dock2-deficient naive CD8+ T cells directly convert into virtual memory cells without clonal effector T cell expansion. This direct conversion to memory is associated with a selective increase in TCR sensitivity to self-peptide MHC in vivo and an enhanced response to weak agonist peptides ex vivo. In contrast, the response to strong agonist peptides remains unaltered in Dock2-deficient T cells. Collectively, these findings suggest that the regulation of the actin dynamics by DOCK2 enhances the threshold for entry into the virtual memory compartment by negatively regulating tonic TCR triggering in response to weak agonists.

CD4+ and CD8+ cytotoxic T lymphocytes may induce mesenchymal cell apoptosis in IgG4-related disease.

BACKGROUND: IgG4-related disease (IgG4-RD) is an immune-mediated fibrotic disorder that has been linked to CD4+ cytotoxic T lymphocytes (CD4+CTLs). The effector phenotype of CD4+CTLs and the relevance of both CD8+ cytotoxic T lymphocytes (CD8+CTLs) and apoptotic cell death remain undefined in IgG4-RD. OBJECTIVE: We sought to define CD4+CTL heterogeneity, characterize the CD8+CTL response in the blood and in lesions, and determine whether enhanced apoptosis may contribute to the pathogenesis of IgG4-RD. METHODS: Blood analyses were undertaken using flow cytometry, cell sorting, transcriptomic analyses at the population and single-cell levels, and next-generation sequencing for the TCR repertoire. Tissues were interrogated using multicolor immunofluorescence. Results were correlated with clinical data. RESULTS: We establish that among circulating CD4+CTLs in IgG4-RD, CD27loCD28loCD57hi cells are the dominant effector subset, exhibit marked clonal expansion, and differentially express genes relevant to cytotoxicity, activation, and enhanced metabolism. We also observed prominent infiltration of granzyme A-expressing CD8+CTLs in disease tissues and clonal expansion in the blood of effector/memory CD8+ T cells with an activated and cytotoxic phenotype. Tissue studies revealed an abundance of cells undergoing apoptotic cell death disproportionately involving nonimmune, nonendothelial cells of mesenchymal origin. Apoptotic cells showed significant upregulation of HLA-DR. CONCLUSIONS: CD4+CTLs and CD8+CTLs may induce apoptotic cell death in tissues of patients with IgG4-RD with preferential targeting of nonendothelial, nonimmune cells of mesenchymal origin.

B lymphocytes directly contribute to tissue fibrosis in patients with IgG4-related disease.

BACKGROUND: IgG4-related disease (IgG4-RD) is a fibroinflammatory condition marked by rapid clinical improvement after selective depletion of B lymphocytes with rituximab. This feature suggests that B cells might participate in fibrogenesis and wound healing. OBJECTIVE: In the present work we aimed to demonstrate that B lymphocytes contribute directly to tissue fibrosis in patients with IgG4-RD. METHODS: Total circulating CD19+ B lymphocytes, naive B cells, memory B cells, or plasmablasts from patients with IgG4-RD were cultivated with human fibroblasts. Profibrotic soluble factors and collagen production in cocultures were assessed by using ELISAs and Luminex assays. RNA sequencing and quantitative RT-PCR were used to assess fibroblast activation in the presence of B cells, as well as induction of profibrotic pathways in B-cell subsets. Relevant profibrotic and inflammatory molecules were confirmed in vitro by using functional experiments and on IgG4-RD tissue sections by using multicolor immunofluorescence studies. RESULTS: B cells from patients with IgG4-RD (1) produced the profibrotic molecule platelet-derived growth factor B and stimulated collagen production by fibroblasts; (2) expressed enzymes implicated in extracellular matrix remodeling, such as lysyl oxidase homolog 2; (3) produced the chemotactic factors CCL4, CCL5, and CCL11; and (4) induced production of these same chemokines by activated fibroblasts. Plasmablasts expressed sets of genes implicated in fibroblast activation and proliferation and therefore represent cells with intrinsic profibrotic properties. CONCLUSION: We have demonstrated that B cells contribute directly to tissue fibrosis in patients with IgG4-RD. These unanticipated profibrotic properties of B lymphocytes, particularly plasmablasts, might be relevant for fibrogenesis in patients with other fibroinflammatory disorders and for wound-healing processes in physiologic conditions.

Identification of galectin-3 as an autoantigen in patients with IgG4-related disease.

BACKGROUND: The antigenic trigger that drives expansion of circulating plasmablasts and CD4+ cytotoxic T cells in patients with IgG4-related disease (IgG4-RD) is presently unknown. OBJECTIVE: We sought to sequence immunoglobulin genes from single-cell clones of dominantly expanded plasmablasts and generate recombinant human mAbs to identify relevant antigens in patients with IgG4-RD by using mass spectrometry. METHODS: Paired heavy and light chain cDNAs from dominant plasmablast clones were expressed as mAbs and used to purify antigens by using immunoaffinity chromatography. Affinity-purified antigens were identified by using mass spectrometry and validated by means of ELISA. Plasma levels of the antigen of interest were also determined by using ELISA. RESULTS: mAbs expressed from the 2 dominant plasmablast clones of a patient with multiorgan IgG4-RD stained human pancreatic tissue sections. Galectin-3 was identified as the antigen specifically recognized by both mAbs. Anti-galectin-3 autoantibody responses were predominantly of the IgG4 isotype (28% of the IgG4-RD cohort, P = .0001) and IgE isotype (11% of the IgG4-RD cohort, P = .009). No significant responses were seen from the IgG1, IgG2, or IgG3 isotypes. IgG4 anti-galectin-3 autoantibodies correlated with increased plasma galectin-3 levels (P = .001), lymphadenopathy (P = .04), total IgG level increase (P = .05), and IgG4 level increase (P = .03). CONCLUSION: Affinity chromatography using patient-derived mAbs identifies relevant autoantigens in patients with IgG4-RD. IgG4 galectin-3 autoantibodies are present in a subset of patients with IgG4-RD and correlate with galectin-3 plasma levels. The marked increases in levels of circulating IgG4 and IgE observed clinically are, at least in part, caused by the development of IgG4- and IgE-specific autoantibody responses.

Sialic acids and autoimmune disease.

An important underlying mechanism that contributes to autoimmunity is the loss of inhibitory signaling in the immune system. Sialic acid-recognizing Ig superfamily lectins or Siglecs are a family of cell surface proteins largely expressed in hematopoietic cells. The majority of Siglecs are inhibitory receptors expressed in immune cells that bind to sialic acid-containing ligands and recruit SH2-domain-containing tyrosine phosphatases to their cytoplasmic tails. They deliver inhibitory signals that can contribute to the constraining of immune cells, and thus protect the host from autoimmunity. The inhibitory functions of CD22/Siglec-2 and Siglec-G and their contributions to tolerance and autoimmunity, primarily in the B lymphocyte context, are considered in some detail in this review. The relevance to autoimmunity and unregulated inflammation of modified sialic acids, enzymes that modify sialic acid, and other sialic acid-binding proteins are also reviewed.

Alterations in sialic-acid O-acetylation glycoforms during murine erythrocyte development.

We used Casd1-deficient mice to confirm that this enzyme is responsible for 9-O-acetylation of sialic acids in vivo. We observed a complete loss of 9-O-acetylation of sialic acid on the surface of myeloid, erythroid and CD4+ T cells in Casd1-deficient mice. Although 9-O-acetylation of sialic acids on multiple hematopoietic lineages was lost, there were no obvious defects in hematopoiesis. Interestingly, erythrocytes from Casd1-deficient mice also lost reactivity to TER-119, a rat monoclonal antibody that is widely used to mark the murine erythroid lineage. The sialic acid glyco-epitope recognized by TER-119 on erythrocytes was sensitive to the sialic acid O-acetyl esterase activity of the hemagglutinin-esterase from bovine coronavirus but not to the corresponding enzyme from the influenza C virus. During erythrocyte development, TER-119+ Ery-A and Ery-B cells could be stained by catalytically inactive bovine coronavirus hemagglutinin-esterase but not by the inactive influenza C hemagglutinin-esterase, while TER-119+ Ery-C cells and mature erythrocytes were recognized by both virolectins. Although the structure of the sialoglycoconjugate recognized by TER-119 was not chemically demonstrated, its selective binding to virolectins suggests that it may be comprised of a 7,9-di-O-acetyl form of sialic acid. As erythrocytes mature, the surfaces of Ery-C cells and mature erythrocytes also acquire an additional distinct CASD1-dependent 9-O-acetyl sialic acid moiety that can be recognized by virolectins from both influenza C and bovine coronavirus.

Lesional CD4+ IFN-γ+ cytotoxic T lymphocytes in IgG4-related dacryoadenitis and sialoadenitis.

OBJECTIVES: IgG4-related disease (IgG4-RD) is a chronic, systemic, inflammatory condition of unknown aetiology. We have recently described clonally expanded circulating CD4+ cytotoxic T lymphocytes (CTLs) in IgG4-RD that infiltrate affected tissues where they secrete interleukin (IL)-1ß and transforming growth factor -ß1 (TGF-ß1). In this study, we sought to examine the role of CD4+ CTLs in the pathogenesis of IgG4-related dacryoadenitis and sialoadenitis (IgG4-DS) and to determine whether these cells secrete interferon-gamma (IFN-γ) at lesional sites. METHODS: Salivary glands of 25 patients with IgG4-DS, 22 patients with Sjögren's syndrome (SS), 12 patients with chronic sialoadenitis (CS) and 12 healthy controls were analysed in this study. Gene expression analysis was performed on submandibular glands (SMGs) from five patients with IgG4-DS, three with CS and three healthy controls. Infiltrating CD4+ CTLs were examined by quantitative multicolour imaging in tissue samples from 20 patients with IgG4-DS, 22 patients with SS, 9 patients with CS and 9 healthy controls. RESULTS: In IgG4-DS tissues, nine genes associated with CD4+ CTLs were overexpressed. The expression of granzyme A (GZMA) mRNA was significantly higher in samples from patients with IgG4-RD compared with corresponding tissues from SS and healthy controls. Quantitative imaging showed that infiltrating CD4+ GZMA+ CTLs were more abundant in patients with IgG4-DS than in the other groups. The ratio of CD4+GZMA+ CTLs in SMGs from patients with IgG4-DS correlated with serum IgG4 concentrations and the number of affected organs. A large fraction of CD4+GZMA+ CTLs in SMGs from patients with IgG4-DS secreted IFN-γ. CONCLUSIONS: The pathogenesis of IgG4-DS is associated with tissue infiltration by CD4+GZMA+ CTLs that secrete IFN-γ.

Clonal expansion of CD4(+) cytotoxic T lymphocytes in patients with IgG4-related disease.

BACKGROUND: IgG4-related disease (IgG4-RD) is a systemic condition of unknown cause characterized by highly fibrotic lesions with dense lymphoplasmacytic infiltrates. CD4(+) T cells constitute the major inflammatory cell population in IgG4-RD lesions. OBJECTIVE: We used an unbiased approach to characterize CD4(+) T-cell subsets in patients with IgG4-RD based on their clonal expansion and ability to infiltrate affected tissue sites. METHODS: We used flow cytometry to identify CD4(+) effector/memory T cells in a cohort of 101 patients with IgG4-RD. These expanded cells were characterized by means of gene expression analysis and flow cytometry. Next-generation sequencing of the T-cell receptor ß chain gene was performed on CD4(+)SLAMF7(+) cytotoxic T lymphocytes (CTLs) and CD4(+)GATA3(+) TH2 cells in a subset of patients to identify their clonality. Tissue infiltration by specific T cells was examined by using quantitative multicolor imaging. RESULTS: CD4(+) effector/memory T cells with a cytolytic phenotype were expanded in patients with IgG4-RD. Next-generation sequencing revealed prominent clonal expansions of these CD4(+) CTLs but not CD4(+)GATA3(+) memory TH2 cells in patients with IgG4-RD. The dominant T cells infiltrating a range of inflamed IgG4-RD tissue sites were clonally expanded CD4(+) CTLs that expressed SLAMF7, granzyme A, IL-1ß, and TGF-ß1. Clinical remission induced by rituximab-mediated B-cell depletion was associated with a reduction in numbers of disease-associated CD4(+) CTLs. CONCLUSIONS: IgG4-RD is prominently linked to clonally expanded IL-1ß- and TGF-ß1-secreting CD4(+) CTLs in both peripheral blood and inflammatory tissue lesions. These active, terminally differentiated, cytokine-secreting effector CD4(+) T cells are now linked to a human disease characterized by chronic inflammation and fibrosis.

Predictors of disease relapse in IgG4-related disease following rituximab.

OBJECTIVE: IgG4-related disease (IgG4-RD) is a relapsing-remitting condition responsible for fibroinflammatory lesions that can lead to organ damage and life-threatening complications at nearly any anatomical site. The duration of remission following treatment varies and predictors of relapse are unclear. The objectives of this study were to review our experience with rituximab as remission induction in IgG4-RD, to clarify the duration of efficacy and to identify predictors of flare following treatment. METHODS: In this retrospective cohort study, all patients were treated with two doses of rituximab (1 g) separated by 15 days. Clinical, radiographic and laboratory data pertaining to rituximab response and disease relapse were collected from the electronic medical record. Kaplan-Meier curves were constructed to estimate the time to disease relapse. Log-rank analyses were performed to compare times to relapse among subgroups. Potential relapse predictors were evaluated with Cox regression analysis. RESULTS: Fifty-seven of 60 patients (95%) had clinical responses to rituximab. Forty-one patients (68%) were treated without glucocorticoids. Twenty-one patients (37%) experienced relapses following treatment at a median time from the first infusion of 244 days. Baseline concentrations of serum IgG4, IgE and circulating eosinophils predicted subsequent relapses, with hazard ratios of 6.2 (95% CI: 1.2, 32.0), 8.2 (95% CI: 1.4, 50.0) and 7.9 (95% CI: 1.8, 34.7), respectively. The higher the baseline values, the greater the risk of relapse and the shorter the time to relapse. Only 10% of the patients had elevations of all three major risk factors, underscoring the importance of measuring all three at baseline. CONCLUSION: Baseline elevations in serum IgG4, IgE and blood eosinophil concentrations all predict IgG4-RD relapses independently.

B-cell depletion attenuates serological biomarkers of fibrosis and myofibroblast activation in IgG4-related disease.

OBJECTIVES: Fibrosis is a predominant feature of IgG4-related disease (IgG4-RD). B-cell depletion induces a prompt clinical and immunological response in patients with IgG4-RD, but the effects of this intervention on fibrosis in IgG4-RD are unknown. We used the enhanced liver fibrosis (ELF) score to address the impact of rituximab on fibroblast activation. The ELF score is an algorithm based on serum concentrations of procollagen-III aminoterminal propeptide, tissue inhibitor of matrix metalloproteinase-1 and hyaluronic acid. METHODS: Ten patients with active, untreated IgG4-RD were enrolled. ELF scores were measured and correlated with the IgG4-RD Responder Index, serum IgG4, circulating plasmablasts and imaging studies. Through immunohistochemical stains for CD3, CD20, IgG4 and α-smooth muscle actin, we assessed the extent of the lymphoplasmacytic infiltration and the degree of fibroblast activation in one patient with tissue biopsies before and after rituximab. RESULTS: The ELF score was increased in patients with IgG4-RD compared with healthy controls (8.3±1.4 vs 6.2±0.9; p=0.002) and correlated with the number of organs involved (R(2)=0.41; p=0.04). Rituximab induced significant reductions in the ELF score, the number of circulating plasmablasts and the IgG4-RD Responder Index (p<0.05 for all three parameters). Rituximab reduced both the lymphoplasmacytic infiltrate and myofibroblast activation. IgG4-RD relapse coincided with recurrent increases in the ELF score, indicating reactivation of collagen deposition. CONCLUSIONS: The ELF score may be a clinically useful indicator of active fibrosis and the extent of disease in IgG4-RD. B-cell depletion has the potential to halt continued collagen deposition by attenuating the secretory phenotype of myofibroblasts in IgG4-RD lesions.

Plasmablasts as a biomarker for IgG4-related disease, independent of serum IgG4 concentrations.

OBJECTIVES: We examined the utility of circulating total and IgG4+ plasmablasts as biomarkers of diagnosis and disease activity in IgG4-related disease (IgG4-RD). MATERIALS METHODS: We evaluated patients with active, untreated, biopsy-proven IgG4-RD affecting various organs. Flow cytometry was used to measure total plasmablast and IgG4+ plasmablast counts by gating peripheral blood for CD19lowCD38+CD20-CD27+ cells and CD19lowCD38+CD20-CD27+IgG4+ cells. Serum IgG4 concentrations were measured by nephelometry. We compared 37 IgG4-RD patients to 35 controls, including healthy individuals (n=14) and patients with other inflammatory diseases before treatment (n=21). RESULTS: The IgG4-RD patients' mean age was 59, and 68% were male. Fourteen patients (38%) had three or more organs involved. The IgG4-RD patients had substantially elevated total plasmablast counts (median 4698/mL, range 610-79524/mL) compared to both untreated disease controls (median 592/mL, range 19-4294/mL; p < 0.001) and healthy controls (median 94/mL, range 1-653/mL; p < 0.001). Thirteen IgG4-RD patients (36%) had normal serum IgG4 concentrations (mean 60 mg/dL, range 5-123 mg/dL, normal <135 mg/dL). However, the median plasmablast count was not significantly lower in that subset with normal serum IgG4 concentrations (3784/mL) compared to those with elevated serum IgG4 (5155/mL) (p = 0.242). Among the 12 rituximab (RTX)-treated patients, the median plasmablast level during disease flare was 6356/mL (range 1123-41589/mL), declining to 1419/mL (range 386/mL-4150/mL) during remission (p < 0.01). CONCLUSIONS: Circulating plasmablasts are elevated in active IgG4-RD, even in patients with normal serum IgG4 concentrations. Plasmablast counts are a potentially useful biomarker for diagnosis, assessing response to treatment, and determining the appropriate time for re-treatment.

De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease.

BACKGROUND: IgG4-related disease (IgG4-RD) is a poorly understood, multiorgan, chronic inflammatory disease characterized by tumefactive lesions, storiform fibrosis, obliterative phlebitis, and accumulation of IgG4-expressing plasma cells at disease sites. OBJECTIVE: The role of B cells and IgG4 antibodies in IgG4-RD pathogenesis is not well defined. We evaluated patients with IgG4-RD for activated B cells in both disease lesions and peripheral blood and investigated their role in disease pathogenesis. METHODS: B-cell populations from the peripheral blood of 84 patients with active IgG4-RD were analyzed by using flow cytometry. The repertoire of B-cell populations was analyzed in a subset of patients by using next-generation sequencing. Fourteen of these patients were longitudinally followed for 9 to 15 months after rituximab therapy. RESULTS: Numbers of CD19(+)CD27(+)CD20(-)CD38(hi) plasmablasts, which are largely IgG4(+), are increased in patients with active IgG4-RD. These expanded plasmablasts are oligoclonal and exhibit extensive somatic hypermutation, and their numbers decrease after rituximab-mediated B-cell depletion therapy; this loss correlates with disease remission. A subset of patients relapse after rituximab therapy, and circulating plasmablasts that re-emerge in these subjects are clonally distinct and exhibit enhanced somatic hypermutation. Cloning and expression of immunoglobulin heavy and light chain genes from expanded plasmablasts at the peak of disease reveals that disease-associated IgG4 antibodies are self-reactive. CONCLUSIONS: Clonally expanded CD19(+)CD27(+)CD20(-)CD38(hi) plasmablasts are a hallmark of active IgG4-RD. Enhanced somatic mutation in activated B cells and plasmablasts and emergence of distinct plasmablast clones on relapse indicate that the disease pathogenesis is linked to de novo recruitment of naive B cells into T cell-dependent responses by CD4(+) T cells, likely driving a self-reactive disease process.

Prevalence of atopy, eosinophilia, and IgE elevation in IgG4-related disease.

IgG4-related disease (IgG4-RD) is a fibroinflammatory disorder that can affect virtually every organ system. T-helper type 2 responses have been presumed to be pathogenic in this disease, and a high proportion of patients with IgG4-RD are reported to have longstanding allergies, peripheral blood eosinophilia, and serum IgE elevation. It has therefore been proposed that allergic mechanisms drive IgG4-RD. However, no epidemiological assessment of atopy, peripheral blood eosinophilia, and serum IgE concentrations has ever been undertaken in patients with IgG4-RD. In this study, we evaluated these parameters in a large cohort of patients with IgG4-RD in whom a wide range of organs were affected by disease. Our results demonstrate that the majority of patients with IgG4-RD are nonatopic. Nevertheless, a subset of nonatopic subjects exhibit peripheral blood eosinophilia and elevated IgE, suggesting that processes inherent to IgG4-RD itself rather than atopy per se contribute to the eosinophilia and IgE elevation observed in the absence of atopy.

Antigen-bearing dendritic cells regulate the diverse pattern of memory CD8 T-cell development in different tissues.

Memory T cells of the effector type (T(EM)) account for the characteristic rapidity of memory T-cell responses, whereas memory T cells of the central type (T(CM)) account for long-lasting, vigorously proliferating memory T-cell responses. How antigen-stimulated (primed) T cells develop into different memory T-cell subsets with diverse tissue distributions is largely unknown. Here we show that after respiratory tract infection of mice with influenza virus, viral antigen associated with dendritic cells (DCs) was abundant in lung-draining lymph nodes (DLN) and the spleen for more than a week but was scant and transient in nondraining lymph nodes (NDLN). Correspondingly, activated CD8 T cells proliferated extensively in DLN and the spleen but minimally in NDLN. Strikingly, however, although most persisting CD8 T cells in DLN and spleen exhibited the T(EM) phenotype, those persisting in NDLN exhibited the T(CM) phenotype. Reducing antigen exposure by depleting DCs at the peak of primary T-cell responses enhanced the development of T(CM), whereas subjecting primed CD8 T cells from NDLN to additional antigen stimulation inhibited T(CM) development. These findings demonstrate that differences in persistence of antigen-bearing DCs in various tissues regulate the tissue-specific pattern of memory CD8 T-cell development. The findings have significant implications for design of vaccines and immunization strategies.

Extrafollicular IgD-CD27-CXCR5-CD11c- DN3 B cells infiltrate inflamed tissues in autoimmune fibrosis and in severe COVID-19.

Although therapeutic B cell depletion dramatically resolves inflammation in many diseases in which antibodies appear not to play a central role, distinct extrafollicular pathogenic B cell subsets that accumulate in disease lesions have hitherto not been identified. The circulating immunoglobulin D (IgD)-CD27-CXCR5-CD11c+ DN2 B cell subset has been previously studied in some autoimmune diseases. A distinct IgD-CD27-CXCR5-CD11c- DN3 B cell subset accumulates in the blood both in IgG4-related disease, an autoimmune disease in which inflammation and fibrosis can be reversed by B cell depletion, and in severe COVID-19. These DN3 B cells prominently accumulate in the end organs of IgG4-related disease and in lung lesions in COVID-19, and double-negative B cells prominently cluster with CD4+ T cells in these lesions. Extrafollicular DN3 B cells may participate in tissue inflammation and fibrosis in autoimmune fibrotic diseases, as well as in COVID-19.

Alternative Methods to Detect Severe Acute Respiratory Syndrome Coronavirus 2 Antibodies.

The COVID-19 pandemic has resulted in the development, validation, and rapid adoption of multiple novel diagnostic approaches. Hundreds of SARS-CoV-2 serologic assays have been developed and deployed to contain the spread of the virus, and to supply timely and important health information. Most of these serologic assays were based on a conventional enzyme-linked immunosorbent assay or the lateral flow assay format. The immunoassays that were developed were based on alternative technologies and are highlighted in this article with a brief discussion of the assay principle and the pros and cons for each assay. Measurement of neutralizing antibodies is also discussed.

Permanent, Antimicrobial Coating to Rapidly Kill and Prevent Transmission of Bacteria, Fungi, Influenza, and SARS-CoV-2.

Microbial adhesion and contamination on shared surfaces can lead to life-threatening infections with serious impacts on public health, economy, and clinical practices. The traditional use of chemical disinfectants for sanitization of surfaces, however, comes with its share of health risks, such as hazardous effects on the eyes, skin, and respiratory tract, carcinogenicity, as well as environmental toxicity. To address this, we have developed a nonleaching quaternary small molecule (QSM)-based sprayable coating which can be fabricated on a wide range of surfaces such as nylon, polyethylene, surgical mask, paper, acrylate, and rubber in a one-step, photocuring technique. This contact-active coating killed pathogenic bacteria and fungi including drug-resistant strains of Staphylococcus aureus and Candida albicans within 15-30 min of contact. QSM coatings withstood multiple washes, highlighting their durability. Interestingly, the coated surfaces exhibited rapid killing of pathogens, leading to the prevention of their transmission upon contact. The coating showed membrane disruption of bacterial cells in fluorescence and electron microscopic investigations. Along with bacteria and fungi, QSM-coated surfaces also showed the complete killing of high loads of influenza (H1N1) and SARS-CoV-2 viruses within 30 min of exposure. To our knowledge, this is the first report of a coating for multipurpose materials applied in high-touch public places, hospital equipment, and clinical consumables, rapidly killing drug-resistant bacteria, fungi, influenza virus, and SARS-CoV-2.