Dysregulated naive B cells and de novo autoreactivity in severe COVID-19.

Severe SARS-CoV-2 infection1 has been associated with highly inflammatory immune activation since the earliest days of the COVID-19 pandemic2-5. More recently, these responses have been associated with the emergence of self-reactive antibodies with pathologic potential6-10, although their origins and resolution have remained unclear11. Previously, we and others have identified extrafollicular B cell activation, a pathway associated with the formation of new autoreactive antibodies in chronic autoimmunity12,13, as a dominant feature of severe and critical COVID-19 (refs. 14-18). Here, using single-cell B cell repertoire analysis of patients with mild and severe disease, we identify the expansion of a naive-derived, low-mutation IgG1 population of antibody-secreting cells (ASCs) reflecting features of low selective pressure. These features correlate with progressive, broad, clinically relevant autoreactivity, particularly directed against nuclear antigens and carbamylated proteins, emerging 10-15 days after the onset of symptoms. Detailed analysis of the low-selection compartment shows a high frequency of clonotypes specific for both SARS-CoV-2 and autoantigens, including pathogenic autoantibodies against the glomerular basement membrane. We further identify the contraction of this pathway on recovery, re-establishment of tolerance standards and concomitant loss of acute-derived ASCs irrespective of antigen specificity. However, serological autoreactivity persists in a subset of patients with postacute sequelae, raising important questions as to the contribution of emerging autoreactivity to continuing symptomology on recovery. In summary, this study demonstrates the origins, breadth and resolution of autoreactivity in severe COVID-19, with implications for early intervention and the treatment of patients with post-COVID sequelae.

Anti-glomerular Basement Membrane Disease: What Have We Learned?

Since the first clinicopathologic description by Ernest Goodpasture of a patient whom he considered to have died of influenza in 1919, substantial progress has been made in our knowledge of anti-glomerular basement membrane disease. This has led to a significant decrease in the morbidity and mortality associated with this disease. In this paper, we aim to review the literature that has enhanced our understanding of classic anti-glomerular basement membrane disease and its clinic-pathologic variants in the key areas of immunopathogenesis and histopathology. We also summarize varied clinical presentations and therapeutic strategies.

Could basement membrane alterations, resembling micro-wounds at the dermo-epidermal junction in psoriatic non-lesional skin, make the skin susceptible to lesion formation?

Current data suggest that tissue microenvironment control immune functions. Therefore, understanding the tissue environment in which immune activation occurs will enhance our capability to interfere with abnormal immune pathology. Here, we argue that studying the constitutively abnormal functions of clinically uninvolved psoriatic skin in patients with plaque type psoriasis is very important to better understand psoriasis pathobiology, because non-lesional skin provides the tissue environment in which the psoriatic lesion develops. A key question in psoriasis is what initiates the abnormal, uncontrolled immune activation in the first place and the answer may lie in the skin. In light of this concept, we summarize abnormalities at the dermal-epidermal junction region which shows a special "non-healing-like" micro-wound phenotype in the psoriatic non-lesional skin that may act as a crucial susceptibility factor in the development of the disease.

The impact of COVID-19 in the management of AL amyloidosis and Immunoglobulin Deposition Disease: A single-center experience.

INTRODUCTION: Patients with AL amyloidosis and immunoglobulin deposition diseases (IDD) are vulnerable during the COVID-19 pandemic due to the immune compromise from the plasma cell disorder and therapy-related immune defects. We describe a local experience in providing care for patients with AL amyloidosis and IDD. METHOD: Patient treatment and disease status since the beginning of the pandemic on March 11, 2020, as declared by WHO, were collected and analyzed. RESULTS: Ninety-six patients with AL amyloidosis and IDD were included. Four patients with IDD and 22 patients with systemic AL amyloidosis were receiving treatment during the pandemic. Since the pandemic, patients' treatments were discontinued if they achieved VGPR or better postinduction. Seven patients discontinued all treatment after achieving VGPR, and others required treatment modifications. 28 patients have been tested for COVID-19, and all tests have been negative. Three patients died since the pandemic, two from organ complications of systemic AL amyloidosis and one from an unrelated cause. CONCLUSION: The management of AL amyloidosis and IDD must be individualized on the clinical characteristics, centers' access to care under the pandemic restrictions, and the epidemiological aspects of the outbreak.

Is primary membranous nephropathy a complement mediated disease?

Membranous nephropathy (MN) is an immune complex mediated disease. Although limited to the kidney, in up to 20% of patients MN is associated with other autoimmune, infectious or malignant diseases. The initial pathogenetic event in what is still considered "primary" MN is the binding of circulating autoantibodies to proteins (autoantigens) expressed in glomerular podocytes. This antibody binding leads to the formation of immune complexes in the glomerular basement membrane. There is clinical and experimental evidence that these immune deposits lead to the activation of the complement system. Experimental studies in the MN model of Heymann's nephritis show that the terminal membrane attack complex (MAC) of the complement system induces a disturbance of the glomerular filtration barrier and leads to proteinuria, the clinical hallmark of MN. After the discovery of the phospholipase A2 receptor 1 and thrombospondin type 1 domain containing protein 7A as endogenous antigens, it is assumed that IgG4 antibodies directed against these proteins induce MN in over 85% of patients with primary MN. As a result, the role of complement in the pathogenesis of MN needs to be defined in light of these developments. In this review we describe the current knowledge on the function of the complement system in primary MN and discuss the open questions, which have to be solved for a better understanding of the potential role of complement in the pathophysiology of primary MN.

Diagnosis of autoimmune subepidermal bullous diseases with mucous membrane involvement based on laser-scanning confocal microscopy.

BACKGROUND: Mucosal involvement in autoimmune subepidermal blistering disorders (ASBD) may represent the only or predominant localization. Circulating autoantibodies are detected in 50% cases. OBJECTIVE: The aim of this study was to evaluate the usefulness of fluorescence overlay antigen mapping by laser-scanning confocal microscopy (FOAM-LSCM) to identify ASBD with mucosal involvement in oral mucosa specimens. MATERIALS & METHODS: Thirty-two ASBD patients, diagnosed based on direct immunofluorescence between 2006 and 2016, were enrolled. Localization of IgG deposits bound at the basement membrane zone, relative to laminin-332 and collagen IV localization, was assessed in vivo. RESULTS: FOAM-LSCM disclosed four different immunofluorescence patterns. IgG deposits were located above laminin-332, as in bullous pemphigoid (BP-type), in 19% cases and co-localized with laminin-332 (anti-laminin-332-type) in 6% cases. IgG deposits were found below laminin-332 and above collagen IV (mucous membrane pemphigoid-type) in 59% cases, and below collagen IV (epidermolysis bullosa acquisita-type) in 16%. Circulating antibodies were found in 56% cases. CONCLUSION: The FOAM-LSCM method should be used in order to obtain a definitive diagnosis of ASBD with mucosal involvement, particularly in the presence of negative circulating antibodies.

A viral infection explanation for Kawasaki disease in general and for COVID-19 virus-related Kawasaki disease symptoms.

SARS-CoV-2, a new virus that appeared in Wuhan, China, in 2019 has approximately an 80% genomic match to the Severe Acute Respiratory Symptom (SARS) virus, which is known to come from a bat virus. Symptoms of Kawasaki disease in general and incomplete Kawasaki disease have been seen in a subset of pediatric patients having a current or previous infection of SARS-CoV-2. A viral infection, such as a SARS-CoV-2 virus infection, could result in extensive antigen-antibody immune complexes that cannot be quickly cleared in a subset of patients and thus create a type III hypersensitivity immune reaction and cause Kawasaki disease or Kawasaki disease symptoms (also known as multisystem inflammatory syndrome) in a subset of patients. Extensive binding of antibodies to viral antigens can create antigen-antibody immune complexes, which, if not eliminated in certain individuals having dysfunctional complement systems, can start inflammatory type III hypersensitivity symptoms, including protease releases that can disrupt epithelium, mesothelium, and endothelium basement membranes, and induce pervasive inflammation throughout the body. This could continue after SARS-CoV-2 infections end if the first wave of protease attacks on basement membranes created new secondary autoantibodies and new uncleared antigen-antibody immune complexes.

Polyclonal immunoglobulin G deposition on the tubular basement membrane in a diabetic nephropathy: A case report.

A 70-year-old Japanese man with diabetes mellitus was referred to our hospital for treatment of renal dysfunction. Renal biopsy revealed that the tubular basement membrane (TBM) showed extreme thickening histologically, and selective polyclonal immunoglobulin G deposition on the thickened TBM, whereas no immunoglobulin deposition was found in the glomeruli in an immunofluorescence study. In electron microscopy, a powdery type of electron dense material, which was similar to that seen in Randall-type monoclonal immunoglobulin deposition disease (MIDD), was observed on the tubular epithelial side of the TBM. However, the present case was differentiated from MIDD, because polyclonal deposition with both kappa and lambda deposition on the TBM was observed. Moreover, there was no noticeable glomerular deposition, which is usually found in cases of MIDD. Anti-TBM disease was also considered as a differential diagnosis, in which polyclonal immunoglobulin deposits selectively on the TBM. However, in the present case, prominent interstitial nephritis was not observed. A similar case with a history of diabetes mellitus has been reported, which was diagnosed as Polyclonal Immunoglobulin G Deposition Disease. No further reports of this case have emerged thereafter; we present this case as the second report supporting this article.

Culture on a native bone marrow-derived extracellular matrix restores the pancreatic islet basement membrane, preserves islet function, and attenuates islet immunogenicity.

Islet transplantation in man is limited by multiple factors including islet availability, islet cell damage caused by collagenase during isolation, maintenance of islet function between isolation and transplantation, and allograft rejection. In this study, we describe a new approach for preparing islets that enhances islet function in vitro and reduces immunogenicity. The approach involves culture on native decellularized 3D bone marrow-derived extracellular matrix (3D-ECM), which contains many of the matrix components present in pancreas, prior to islet transplantation. Compared to islets cultured on tissue culture plastic (TCP), islets cultured on 3D-ECM exhibited greater attachment, higher survival rate, increased insulin content, and enhanced glucose-stimulated insulin secretion. In addition, culture of islets on 3D-ECM promoted recovery of vascular endothelial cells within the islets and restored basement membrane-related proteins (eg, fibronectin and collagen type VI). More interestingly, culture on 3D-ECM also selectively decontaminated islets of "passenger" cells (co-isolated with the islets) and restored basement membrane-associated type VI collagen, which were associated with an attenuation in islet immunogenicity. These results demonstrate that this novel approach has promise for overcoming two major issues in human islet transplantation: (a) poor yield of islets from donated pancreas tissue and (b) the need for life-long immunosuppression.

Conjunctival Biopsy Site in Mucous Membrane Pemphigoid.

PURPOSE: To investigate if there is an association between the location of the conjunctival biopsy site (lesional, perilesional, or nonaffected) and the result of the direct immunofluorescence (DIF) test in patients with suspected mucous membrane pemphigoid (MMP) involving the ocular surface. DESIGN: Retrospective case series. METHODS: Records of patients with clinically suspected ocular MMP were reviewed to determine the location of the conjunctival biopsy. Conjunctival biopsy locations were defined as "lesional," "perilesional," and "nonaffected" conjunctiva. The DIF was considered positive when there was deposition of at least 1 of either IgM, IgG, IgA, or C3 at the basement membrane of the specimen; nondiagnostic when only fibrinogen was found at the same location; and negative when none of these features were present. RESULTS: The records of 41 patients were analyzed. Of these, 32 were eligible to be included in the study. Biopsies were lesional in 22% of cases (7/32), perilesional in 22% (7/32), and from nonaffected conjunctiva in 56% (18/32). DIF results were positive in 14% of lesional biopsies, in 86% of perilesional biopsies, and in 17% of those from nonaffected conjunctiva (P = .003). Perilesional biopsies gave higher positive DIF than lesional biopsies (P = .029). CONCLUSIONS: Perilesional conjunctival biopsies are associated with an increase in positive DIF results. These results support the need to sample perilesional conjunctival tissue in patients with suspected MMP.

Ectodermal Dysplasia: Association with Anti-Basement Membrane Autoantibodies.

Ectodermal dysplasia (ED) is a group of several genetic conditions with absence or dysgenesis of at least two ectodermal derivatives: teeth, skin and its appendages including hair, nails, eccrine and sebaceous glands. The most important clinical findings in patients with ED are hypodontia, hypotrichosis, and hypohidrosis, which can lead to episodes of hyperthermia. Few reports have focused on the progressive keratopathy in ED. Cicatrizing conjunctivitis associated with anti-basement membrane autoantibodies has been described. We report a series of three ectodermal dysplasia patients with an ocular phenotype typically seen in ocular mucous membrane pemphigoid; conjunctival immunohistopathology revealed anti-basement membrane autoantibodies in all of them, and systemic immunosuppression proved to be effective in improving symptoms and helping to stabilize ocular surface disease.

Complement Activation in Autoimmune Bullous Dermatoses: A Comprehensive Review.

Autoimmune bullous dermatoses (AIBD) are characterized by circulating autoantibodies that are either directed against epidermal antigens or deposited as immune complexes in the basement membrane zone (BMZ). The complement system (CS) can be activated by autoantibodies, thereby triggering activation of specific complement pathways. Local complement activation induces a pathogenic inflammatory response that eventually results in the formation of a sub- or intraepidermal blister. Deposition of complement components is routinely used as a diagnostic marker for AIBD. Knowledge from different animal models mimicking AIBD and deposition of complement components in human skin biopsies provides more insight into the role of complement in the pathogenesis of the different AIBD. This review outlines the role of the CS in several AIBD including bullous pemphigoid, epidermolysis bullosa acquisita, mucous membrane pemphigoid (MMP), pemphigus, linear IgA-disease, and dermatitis herpetiformis. We also discuss potential therapeutic approaches targeting key complement components, pathways and pathogenic complement-mediated events.

Role and Molecular Mechanisms of Pericytes in Regulation of Leukocyte Diapedesis in Inflamed Tissues.

Leukocyte recruitment is a hallmark of the inflammatory response. Migrating leukocytes breach the endothelium along with the vascular basement membrane and associated pericytes. While much is known about leukocyte-endothelial cell interactions, the mechanisms and role of pericytes in extravasation are poorly understood and the classical paradigm of leukocyte recruitment in the microvasculature seldom adequately discusses the involvement of pericytes. Emerging evidence shows that pericytes are essential players in the regulation of leukocyte extravasation in addition to their functions in blood vessel formation and blood-brain barrier maintenance. Junctions between venular endothelial cells are closely aligned with extracellular matrix protein low expression regions (LERs) in the basement membrane, which in turn are aligned with gaps between pericytes. This forms preferential paths for leukocyte extravasation. Breaching of the layer formed by pericytes and the basement membrane entails remodelling of LERs, leukocyte-pericyte adhesion, crawling of leukocytes on pericyte processes, and enlargement of gaps between pericytes to form channels for migrating leukocytes. Furthermore, inflamed arteriolar and capillary pericytes induce chemotactic migration of leukocytes that exit postcapillary venules, and through direct pericyte-leukocyte contact, they induce efficient interstitial migration to enhance the immunosurveillance capacity of leukocytes. Given their role as regulators of leukocyte extravasation, proper pericyte function is imperative in inflammatory disease contexts such as diabetic retinopathy and sepsis. This review summarizes research on the molecular mechanisms by which pericytes mediate leukocyte diapedesis in inflamed tissues.

Monoclonal immunoglobulin G deposits on tubular basement membrane in renal allograft: is this significant for chronic allograft injury?

BACKGROUND: Tubular basement membrane immune deposits (TBMID) has rarely been observed in renal allografts. It is usually found in BK virus nephropathy and immune complex glomerulonephritis; however, its significance is not well understood. We conducted a retrospective clinicopathological study on monoclonal immunoglobulin G (IgG) TBMID. METHODS: We studied 7177 renal allograft biopsy specimens obtained from Tokyo Women's Medical University from 2007 to 2015 and performed light microscopic, electron microscopic and immunofluorescence studies. RESULTS: Tubular basement membrane (TBM) deposits of IgG were found in 73 biopsies from 61 patients and the IgG subclass was obtained in 31 biopsies. There were no cases of monoclonal IgA or IgM TBMID. In total, 13 biopsies from 10 patients showed monoclonal IgG TBMID. Of these, seven showed monoclonal IgG1κ TBMID and one each showed monoclonal IgG2κ, IgG2λ and IgG3κ TBMID. Conversely, eight patients showed polyclonal IgG TBMID. In electron microscopy, large granular electron-dense deposits (EDDs) in the TBM were detected in all patients with monoclonal IgG1κ TBMID. EDDs were absent in TBM in patients with monoclonal IgG2κ, IgG2λ or IgG3κ TBMID. Progression of interstitial fibrosis and tubular atrophy (IFTA) was significantly higher in patients with monoclonal IgG1κ TBMID than in those with polyclonal IgG TBMID (P < 0.05). There were no significant differences in the other clinical parameters between monoclonal IgG1κ and polyclonal IgG TBMID. CONCLUSIONS: This is the first study of patients with monoclonal IgG TBMID in renal allografts. We found that monoclonal IgG1κ TBMID was associated with EDD formation in TBM and IFTA progression.

Standardized classification and reporting of glomerulonephritis.

A kidney biopsy is done to determine the etiology of the glomerulonephritis (GN) and the severity of the lesion, to identify whether other lesions, related to or not related to the GN, are present on the kidney biopsy and finally to ascertain the extent of chronicity of the GN. The etiology of GN is based on the classification of GN into five groups: immune complex-mediated GN, antineutrophil cytoplasmic antibody (ANCA)-associated GN, anti-glomerular basement membrane (GBM) GN, monoclonal immunoglobulin-mediated GN and C3 glomerulopathy. Immune complex GN includes multiple specific diseases such as lupus nephritis, IgA nephropathy, infection-related GN and fibrillary GN. ANCA GN, anti-GBM GN and C3 glomerulopathy are specific diseases in themselves, while monoclonal Ig GN includes proliferative GN with monoclonal Ig deposits and monoclonal Ig deposition disease. Thus identification of the class of GN and within it the specific disease determines the etiology of GN. Ancillary studies may be required to confirm the etiology of GN. The severity of the GN is revealed by the pattern of injury, such as crescentic, necrotizing, diffuse proliferative, exudative, membranoproliferative, mesangial proliferative or a sclerosing GN. Secondary diagnosis either related or unrelated to the GN, such as diabetic glomerulosclerosis, acute tubular necrosis or thrombotic microangiopathy, may also be present. The secondary diagnosis may sometimes be the reason for the kidney biopsy. The chronicity of GN is determined by evaluating the extent of glomerulosclerosis, tubular atrophy and interstitial fibrosis and vascular sclerosis present on the biopsy. This review summarizes the approach to standardizing a kidney biopsy report that includes these components in a logical and sequential manner.

High Expression of Collagen XVII Compensates for its Depletion Induced by Pemphigoid IgG in the Oral Mucosa.

The basement membrane zone consists of multiple components, including collagen XVII (COL17), which is the target of bullous pemphigoid. To our knowledge, no research has addressed the differences in basement membrane zone components between the skin and oral mucosa; therefore, we investigated the basement membrane zone proteins, with a focus on COL17. The mRNA and protein expression levels of COL17 were significantly higher in oral keratinocytes than in skin keratinocytes. Hemidesmosomal COL17 expression was markedly higher in oral keratinocytes than in skin keratinocytes, and its level was associated with adhesion strength. Oral keratinocytes adhered to the extracellular matrix more tightly than did skin keratinocytes in vitro. Based on these results, we attempt to explain the clinical diversity of bullous pemphigoid. COL17 depletion was more prominent in skin keratinocytes than in oral keratinocytes after treatment with COL17-NC16A mAbs, which have in vivo pathogenicity. COL17 C-terminus mAbs, which are not pathogenic, facilitated COL17 depletion in combination treatment with COL17-NC16A mAbs in both types of keratinocytes. In summary, the greater amount of COL17 in oral keratinocytes than in skin keratinocytes is associated with the higher strength of oral keratinocyte hemidesmosomal adhesion at the basement membrane zone. Our results may explain why bullous pemphigoid blistering tends to be more prevalent in the skin than in the oral mucosa.