Phylogeny, Structure, Functions, and Role of AIRE in the Formation of T-Cell Subsets

It is well known that the most important feature of adaptive immunity is the specificity that provides highly precise recognition of the self, altered-self, and non-self. Due to the high specificity of antigen recognition, the adaptive immune system participates in the maintenance of genetic homeostasis, supports multicellularity, and protects an organism from different pathogens at a qualitatively different level than innate immunity. This seemingly simple property is based on millions of years of evolution that led to the formation of diversification mechanisms of antigen-recognizing receptors and later to the emergence of a system of presentation of the self and non-self antigens. The latter could have a crucial significance because the presentation of nearly complete diversity of auto-antigens in the thymus allows for the “calibration” of the forming repertoires of T-cells for the recognition of self, altered-self, and non-self antigens that are presented on the periphery. The central role in this process belongs to promiscuous gene expression by the thymic epithelial cells that express nearly the whole spectrum of proteins encoded in the genome, meanwhile maintaining their cellular identity. This complex mechanism requires strict control that is executed by several transcription factors. One of the most important of them is AIRE. This noncanonical transcription factor not only regulates the processes of differentiation and expression of peripheral tissue-specific antigens in the thymic medullar epithelial cells but also controls intercellular interactions in the thymus. Besides, it participates in an increase in the diversity and transfer of presented antigens and thus influences the formation of repertoires of maturing thymocytes. Due to these complex effects, AIRE is also called a transcriptional regulator. In this review, we briefly described the history of AIRE discovery, its structure, functions, and role in the formation of antigen-recognizing receptor repertoires, along with other transcription factors. We focused on the phylogenetic prerequisites for the development of modern adaptive immunity and emphasized the importance of the antigen presentation system.

CD138 Expression Promotes Accumulation and Activation of T Cells in Autoimmune MRL/lpr Mice

CD138+ T cells that accumulated in Fas-deficiency lupus mice, had been identified as autoreactive T cells in SLE which significantly promoted autoantibody secretion. In present study, we found CD138 expression in T cells played a key role in the progression of SLE in MRL/lpr mice. Our results indicated CD138+ T cells apoptosis was in Fas dependent way. However, CD138 expression of T cells in MRL/lpr mice could significantly prevent T cells apoptosis, contribute to accumulation of T cells and DN T cells and simultaneously promote T cells activation. Importantly, CD138 expression in DN T cells significantly increased FasL expression of DN T cells enhancing the cytotoxity of DN T cells. Phorbol 12-myristate 13-acetate and Ionomycin (PI) stimulation could significantly prevent CD138+ T cells accumulation by strikingly inducing their specific apoptosis. Moreover, PI stimulation significantly activated CD138+ T cells with increased CD69 expression in them. Importantly, our results showed CD69 expression in CD138+ T cells could significantly increase the apoptosis level of them. That indicated PI stimulation could induce specific apoptosis of CD138+ T cells via increasing CD69 expression in CD138+ T cells. In addition, our results showed CD138- T cells in MRL/lpr mice had significant defects in activation. However, to activate T cells could significantly prevent CD138 expression in CD3+ T cells of MRL/lpr mice. Our results suggested CD138 expression in CD3+ T cells of MRL/lpr mice was probably caused by the failure of activation in autoreactive T cells before self-antigens exposure to immune system.

Recent Advances in Unveiling the Role of Beta-Herpesviruses in Autoimmune Diseases

A dysregulated immune response can lead to recognition of self-antigens as non-self-antigens, leading to failure of the immune tolerance toward normal cells and tissues, and the consequent development of a variety of autoimmune diseases [...]

P03.07 Analysis of scRNAseq from the human thymus nominates genes potentially missing from central tolerance of cytotoxic T cells

BackgroundDuring thymic development, cytotoxic T cells that can bind to and attack self antigens undergo negative selection thus preventing damage to the self tissues. The sparse medullar thymic epithelial cells (mTECs) present in the thymus are responsible for presenting self antigens to T cells so that they can trigger apoptosis or differentiation into non-cytotoxic lineages if they bind too strongly.Materials and MethodsUnderstanding gene expression in mTECs is essential for understanding the shape of the human T cell receptor repertoire, which is key for current and emerging cancer immunotherapies. Recent availability of human thymus single cell RNAseq (scRNAseq) data provides an extremely high-resolution view into the pattern of expression within this critical cell type. To determine which epitopes have had to opportunity to be presented during T cell negative selection, we analyzed the human thymus scRNAseq dataset to establish which genes are expressed in mTECs and therefore subject to central tolerance.ResultsThe coverage of the whole transcriptome of a particular cell is generally sparse. It is therefore difficult to understand basic features of individual cells or cell types such as how many genes are expressed. We used cell- and read-level subsampling to estimate whether a sufficient number of cells and reads had been captured to support categorizing a gene as non-expressed in mTECs. We also examined the expression of the genes not expressed in mTECs in other healthy tissues, and found their expression was almost exclusively restricted to the testis (an immune-privileged site) and the liver (a site of peripheral tolerance)ConclusionsAltogether, these analyses establish a strategy for determining if a data set has sufficient depth to estimate the total number of genes expressed and secondly define a key list of genes that are not expressed during central tolerization of T cells, which represent a compelling list of possible cancer immunotherapy targets.Disclosure InformationL. Blumenberg: A. Employment (full or part-time); Significant; Regeneron Pharmaceuticals. G. Atwal: A. Employment (full or part-time); Significant; Regeneron Pharmaceuticals. A. Dhanik: A. Employment (full or part-time); Significant; Regeneron Pharmaceuticals.

A model of preferential pairing between epithelial and dendritic cells in thymic antigen transfer

Medullary thymic epithelial cells (mTECs) which produce and present self-antigens are essential for the establishment of central tolerance. Since mTEC numbers are limited, their function is complemented by thymic dendritic cells (DCs), which transfer mTEC-produced self-antigens via cooperative antigen transfer (CAT). While CAT is required for effective T cell selection, many aspects remain enigmatic. Given the recently described heterogeneity of mTECs and DCs, it is unclear whether the antigen acquisition from a particular TEC subset is mediated by preferential pairing with specific subset of DCs. Using several relevant Cre-based mouse models controlling the expression of fluorescent proteins, we found that in regards to CAT, each subset of thymic DCs preferentially targets distinct mTEC subset(s) and importantly, XCR1+ activated DCs represented the most potent subset in CAT. Interestingly, one thymic DC can acquire antigen repetitively and of these, monocyte-derived DCs (moDC) were determined to be the most efficient in repetitive CAT. moDCs also represented the most potent DC subset in the acquisition of antigen from other DCs. These findings suggest a preferential pairing model for the distribution of mTEC-derived antigens among distinct populations of thymic DCs.

801 EXOSOMES CONTAINING LUNG SELF-ANTIGENS COLLAGEN-V AND Kα1-TUBULIN ARE PREVALENT IN PATIENTS WITH SYMPTOMATIC GASTROESOPHAGEAL REFLUX: RESULTS FROM A PILOT STUDY

Gastroesophageal reflux disease (GERD) has been associated with aspiration-induced pulmonary injury; however, good clinical or laboratory markers are not available. Increased serum levels of exosomes containing normally sequestered primary lung self-antigens (collagen-V, Kα1-tubulin) have been associated with lung injury in the lung transplant population. The aim of this pilot study was to assess the prevalence of exosomes containing collagen-V and/or Kα1-tubulin in patients with severe GERD. Methods After IRB approval, the institutional biobank database was queried to identify non-lung transplant patients who underwent primary anti-reflux surgery (ARS) from 2019 to 2020. Serum samples were retrieved from the repository. Exosome pellets were isolated using the Invitrogen® kit using the manufacturer’s protocol. The size of exosomes in the pellet was confirmed using NanoSight. Western blot of the exosomes was used to isolate and quantify collagen-V and Kα1-tubulin, using CD-9 as the standard. A ratio > 1 was considered abnormal. Results Ten patients (6 females) with a median (IQR) age of 53 (42, 63) years were included in this study. All patients had symptomatic GERD as an indication for ARS. Five patients (50%) had exosomes containing abnormal levels of collagen-V and/or Kα1-tubulin (Figure 1). There was a mean 2.9- and 8.2-fold increase in collagen-V and Kα1-tubulin, respectively. Conclusion Humoral factors associated with lung injury are highly prevalent in patients undergoing elective ARS for GERD. This suggests that detection of exosomes containing lung self-antigens collagen-V and Kα1-tubulin could be useful as a biomarker of GERD-induced lung injury.

Adaptive Immunity and the Risk of Autoreactivity in COVID-19

While first and foremost considered a respiratory infection, COVID-19 can result in complications affecting multiple organs. Immune responses in COVID-19 can both protect against the disease as well as drive it. Insights into these responses, and specifically the targets being recognised by the immune system, are of vital importance in understanding the side effects of COVID-19 and associated pathologies. The body’s adaptive immunity recognises and responds against specific targets (antigens) expressed by foreign pathogens, but not usually to target self-antigens. However, if the immune system becomes dysfunctional, adaptive immune cells can react to self-antigens, which can result in autoimmune disease. Viral infections are well reported to be associated with, or exacerbate, autoimmune diseases such as multiple sclerosis (MS) and systemic lupus erythematosus (SLE). In COVID-19 patients, both new onset MS and SLE, as well as the occurrence of other autoimmune-like pathologies, have been reported. Additionally, the presence of autoantibodies, both with and without known associations to autoimmune diseases, have been found. Herein we describe the mechanisms of virally induced autoimmunity and summarise some of the emerging reports on the autoimmune-like diseases and autoreactivity that is reported to be associated with SARS-CoV-2 infection.

Myocarditis with COVID-19 mRNA Vaccines

Myocarditis has been recognized as a rare complication of coronavirus 2019 (COVID-19) mRNA vaccinations, especially in young adult and adolescent males. According to the U.S. Centers for Disease Control (CDC), myocarditis/pericarditis rates are approximately 12.6 cases per million doses of second dose mRNA vaccine among 12-39-year-olds. In reported cases, patients with myocarditis invariably presented with chest pain, usually 2-3 days after a second dose of mRNA vaccination and had elevated cardiac troponin levels. ECG was abnormal with ST elevations in most, and cardiac MRI was suggestive of myocarditis in all tested patients. There was no evidence of acute COVID-19 or other viral infections. In one case, a cardiomyopathy gene panel was negative, but autoantibody levels against certain self-antigens and frequency of natural killer cells were increased. Although the mechanisms for development of myocarditis are not clear, molecular mimicry between the spike protein of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and self-antigens, trigger of preexisting dysregulated immune pathways in certain individuals, immune response to mRNA and activation of immunological pathways, and dysregulated cytokine expression have been proposed. The reasons for male predominance in myocarditis cases are unknown, but possible explanations relate to sex hormone differences in immune response and myocarditis, and also under-diagnosis of cardiac disease in women. Almost all patients had resolution of symptoms and signs, and improvement in diagnostic markers and imaging with or without treatment. Despite rare cases of myocarditis, the benefit-risk assessment for COVID-19 vaccination shows a favorable balance for all age and sex groups; therefore COVID-19 vaccination is recommended for everyone 12 years of age and older.

Evaluation of antibodies directed against two GPCRs, anti-AT1R and anti-ETAR, on kidney transplant outcome: Own experience and review of the topic

Background: The role of an alloimmune response against non-self-antigens is established in organ transplantation. The main actors of this recognition are the HLA incompatibilities between donor and recipient, but may also involve reactivity against other alloantigens expressed on the allograft and result from an autoimmune response developed against self-antigens. Objective: Our study aimed to determine the presence of non-anti-HLA antibodies (anti-AT1R and anti-ETAR) in sera from patients with end-stage renal disease who underwent kidney transplantation in pre-and post-transplantation samples and study their influence on the development and evolution of acute humoral rejections and DSAs. Method: In this sense, antibodies (Abs) against two G protein-coupled receptors (GPCRs), angiotensin II type 1 receptor (AT1R) and endothelin-1 type A receptor (ETAR), have been detected in the sera of transplant recipients who experience allograft dysfunction, patients with coronary heart disease, marginal hypertension and refractory, vascular lesions, myocardial hypertrophy and chronic inflammatory diseases such as atherosclerosis or sclerosis. Results: In our own experience, kidney graft recipients were monitored for anti-ETAR, -AT1R, and -HLA Abs in pre-and post-transplant evolution, and anti-AT1R and/or -ETAR Abs were detected in 24% of recipients (22.4% with anti-AT1R Abs and 9.8% with anti-ETAR Abs). Due to acute humoral rejection, Graft loss was detected in 6.4% of patients with anti-GPCRs non-HLA Abs, and 3.2% had DSA anti-HLA Abs. In this research and review paper, we bring together our own experience, also how to function the anti-GPCRs autoAbs and how these Abs that activate GPCRs could influence graft outcome. Conclusion. Therefore, in conclusion, there is a high association of non-HLA anti-GPCRs Abs levels with reduced kidney function after transplantation, especially in the presence of DSA anti-HLA Abs. Although more studies are needed, anti-AT1R and anti-ETAR antibodies may be helpful biomarkers that allow the risk of graft loss to be assessed.