An engineered human cardiac tissue model reveals contributions of systemic lupus erythematosus autoantibodies to myocardial injury

Systemic lupus erythematosus (SLE) is a highly heterogenous autoimmune disease that affects multiple organs, including the heart. The mechanisms by which myocardial injury develops in SLE, however, remain poorly understood. Here we engineered human cardiac tissues and cultured them with IgG fractions containing autoantibodies from SLE patients with and without myocardial involvement. We observed unique binding patterns of IgG from two patient subgroups: (i) patients with severe myocardial inflammation exhibited enhanced binding to apoptotic cells within cardiac tissues subjected to stress, and (ii) patients with systolic dysfunction exhibited enhanced binding to the surfaces of viable cardiomyocytes. Functional assays and RNA sequencing (RNA-seq) revealed that IgGs from patients with systolic dysfunction exerted direct effects on engineered tissues in the absence of immune cells, altering tissue cellular composition, respiration and calcium handling. Autoantibody target characterization by phage immunoprecipitation sequencing (PhIP-seq) confirmed distinctive IgG profiles between patient subgroups. By coupling IgG profiling with cell surface protein analyses, we identified four pathogenic autoantibody candidates that may directly alter the function of cells within the myocardium. Taken together, these observations provide insights into the cellular processes of myocardial injury in SLE that have the potential to improve patient risk stratification and inform the development of novel therapeutic strategies.

PD-1 signaling uncovers a pathogenic subset of T cells in inflammatory arthritis

Background

PD-1 is an immune checkpoint on T cells and interventions to block this receptor result in T cell activation and enhanced immune response to tumors. Paired to that, and despite a decade of research, approaches to treat autoimmunity with PD-1 agonists still need to be more successful. To resolve this, new methods must be developed to augment PD-1 function beyond engaging the receptor.

Methods

We conducted a flow cytometry analysis of T cells isolated from the peripheral blood and synovial fluid of patients with rheumatoid arthritis. In addition, we performed a genome-wide CRISPR/Cas9 screen to identify genes associated with PD-1 signaling. We further analyzed genes involved in PD-1 signaling using publicly available bulk and single-cell RNA sequencing datasets.

Results

Our screen confirmed known regulators in proximal PD-1 signaling and, importantly, found an additional 1,112 unique genes related to PD-1 ability to inhibit T cell functions. These genes were strongly associated with the response of cancer patients to PD-1 blockades and with high tumor immune dysfunction and exclusion scores, confirming their role downstream of PD-1. Functional annotation revealed that more significant genes uncovered were those associated with known immune regulation processes. Remarkably, these genes were considerably downregulated in T cells isolated from patients with inflammatory arthritis, supporting their overall inhibitory functions. A study of rheumatoid arthritis single-cell RNA sequencing data demonstrated that five genes, KLRG1, CRTAM, SLAMF7, PTPN2, and KLRD1, were downregulated in activated and effector T cells isolated from synovial fluids. Back-gating these genes to canonical cytotoxic T cell signatures revealed PD-1 + HLA-DR HIGH KLRG LOW T cells as a novel inflammatory subset of T cells.

Conclusion

We concluded that PD-1 + HLA-DR HIGH KLRG LOW T cells are a potential target for future PD-1 agonists to treat inflammatory diseases. Our study uncovers new genes associated with PD-1 downstream functions and, therefore, provides a comprehensive resource for additional studies that are much needed to characterize the role of PD-1 in the synovial subset of T cells.

Baseline peripheral T-cell composition in relation to radiographic phenotypes of immune-related pneumonitis

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Background: Pneumonitis is one of the most morbid complications from immune checkpoint inhibitor (ICI) treatment, but pathogenic mechanisms are unclear and no biomarkers permit pre-treatment risk assessment. We sought to characterize peripheral T cell subsets of pneumonitis patients on the single cell level. Methods: Blood was collected before and during ICI treatment in 24 patients. Cells were processed for single cell RNA sequencing (scRNAseq) employing CITEseq methodology using multiplexed cell surface markers labelled with a cocktail of oligonucleotide-tagged Total-Seq anti-human antibodies against CD4, CD8, CD45RA and CD27 followed by Chromium 10X sequencing. Principal Component Analysis was performed with iCellR, K-nearest-neighbor-based Network graph drawing Layout, and PhenoGraph clustering to assign cell types. CT scans were performed per standard of care and were reviewed by an experienced thoracic radiologist. Results: Seven of 24 patients developed pneumonitis; 9 did not experience an immune-related adverse event, and the remainder experienced arthritis (4), thyroiditis (3), or neurotoxicity (1). Pneumonitis patients had expanded proportions of TH2 TCF7+ T cells at baseline as compared to the other patients. Radiographically, two patients’ pneumonitis manifested as Chronic Hypersensitivity Pneumonitis (CHP), and four had Organized Pneumonia (OP). At baseline, CHP patients had significantly lower levels of CD8+ TCM cells (CXCR3+), double-positive T cells, gamma-delta T cells, and higher levels of naïve-like CD4+ TN TCF7+LEF1+ and CD4+ TH1/2 CXCR3+GATA3+ cells compared to OP. Gene expression levels also distinguished between these radiographic phenotypes. Conclusions: The peripheral T cell composition of patients who developed pneumonitis was distinct from those who did not in our cohort and unique by radiographic manifestation, suggesting potential pathogenic mechanisms and a prelude to circulating predictive markers of ICI toxicity.

Upregulation of type 1 conventional dendritic cells implicates antigen cross-presentation in multisystem inflammatory syndrome

Background

Multisystem inflammatory syndrome in children (MIS-C) is an acute, febrile, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-associated syndrome, often with cardiohemodynamic dysfunction. Insight into mechanism of disease is still incomplete.

Objective

Our objective was to analyze immunologic features of MIS-C patients compared to febrile controls (FC).

Methods

MIS-C patients were defined by narrow criteria, including having evidence of cardiohemodynamic involvement and no macrophage activation syndrome. Samples were collected from 8 completely treatment-naive patients with MIS-C (SARS-CoV-2 serology positive), 3 patients with unclassified MIS-C–like disease (serology negative), 14 FC, and 5 MIS-C recovery (RCV). Three healthy controls (HCs) were used for comparisons of normal range. Using spectral flow cytometry, we assessed 36 parameters in antigen-presenting cells (APCs) and 29 in T cells. We used biaxial analysis and uniform manifold approximation and projection (UMAP).

Results

Significant elevations in cytokines including CXCL9, M-CSF, and IL-27 were found in MIS-C compared to FC. Classic monocytes and type 2 dendritic cells (DCs) were downregulated (decreased CD86, HLA-DR) versus HCs; however, type 1 DCs (CD11c⁺CD141⁺CLEC9A⁺) were highly activated in MIS-C patients versus FC, expressing higher levels of CD86, CD275, and atypical conventional DC markers such as CD64, CD115, and CX3CR1. CD169 and CD38 were upregulated in multiple monocyte subtypes. CD56^dim/CD57⁻/KLRG^hi/CD161⁺/CD38⁻ natural killer (NK) cells were a unique subset in MIS-C versus FC without macrophage activation syndrome.

Conclusion

Orchestrated by complex cytokine signaling, type 1 DC activation and NK dysregulation are key features in the pathophysiology of MIS-C. NK cell findings may suggest a relationship with macrophage activation syndrome, while type 1 DC upregulation implies a role for antigen cross-presentation.

Role of the thymus in spontaneous development of a multi-organ autoimmune disease in human immune system mice

We evaluated the role of the thymus in development of multi-organ autoimmunity in human immune system (HIS) mice. T cells were essential for disease development and the same T cell clones with varying phenotypes infiltrated multiple tissues. De novo-generated hematopoietic stem cell (HSC)-derived T cells were the major disease drivers, though thymocytes pre-existing in grafted human thymi contributed if not first depleted. HIS mice with a native mouse thymus developed disease earlier than thymectomized mice with a thymocyte-depleted human thymus graft. Defective structure in the native mouse thymus was associated with impaired negative selection of thymocytes expressing a transgenic TCR recognizing a self-antigen. Disease developed without direct recognition of antigens on recipient mouse MHC. While human thymus grafts had normal structure and negative selection, failure to tolerize human T cells recognizing mouse antigens presented on HLA molecules may explain eventual disease development. These new insights have implications for human autoimmunity and suggest methods of avoiding autoimmunity in next-generation HIS mice.

The many faces of psoriatic arthritis: their genetic determinism

In this review, we propose a model of PsA as a complex genetically determined autoimmune-mediated disease having a heterogeneous variety of subphenotypes, with each subphenotype under the control of a different susceptibility-associated HLA allele. Since the specific HLA molecules encoded by each susceptibility allele dominantly select a T cell repertoire with the property of recognizing different peptides, we hypothesize each subphenotype reflects a distinct adaptive autoimmune response directed to different target molecules that is mediated by T cells within each selected repertoire. The interaction among the patients’ susceptibility alleles in the selection of their T cell repertoires determines a spectrum of overall clinical disease severity, varying from mild to severe. We further speculate that these different immune responses may result in activation of different immune effector pathways, which might therefore respond differently to various specific biologic agents.

Endomyocardial biopsies in the diagnosis of myocardial involvement in systemic lupus erythematosus

BACKGROUND

Endomyocardial biopsy (EMB) is considered the gold standard for diagnosing myocardial involvement in most inflammatory conditions, including systemic lupus erythematosus (SLE). However, EMBs are rarely performed, and most of the myocardial histopathology reports in SLE consist of postmortem data. We therefore sought to describe the histopathologic findings of contemporary EMBs in SLE performed in clinical practice.

METHODS

A retrospective review of histopathology reports from SLE patients who underwent EMB from 1994 to 2017 was performed. A total of 41 SLE patients had cardiac pathology reports. Of these, 11 histopathology reports were EMBs, and the remaining were valvular specimens.

RESULTS

A total of 11 SLE EMBs were reviewed. It was found that 45% of the patients had hypertension, 27% had coronary artery disease, 9% had hyperlipidemia, and 36% had end-stage renal disease. None had diabetes or smoked. The mean left ventricular ejection fraction was 37%. On histopathology, 10 had mild interstitial fibrosis, 9 had myocyte hypertrophy, 3 had organized blood clots, and 3 had a mild infiltration of lymphocytes and macrophages without clear evidence of myocarditis. None had vasculitis, endocarditis, ischemia, amyloid deposition, or lamellar or curvilinear inclusions.

CONCLUSION

EMBs are rarely performed in SLE. In this case series, nonspecific interstitial fibrosis and myocyte hypertrophy were the most common findings, suggesting EMBs have limited value in the diagnosis of cardiac involvement in SLE and rather rule out competing conditions. These data support the need for diagnostic methods with high sensitivity and specificity for SLE heart disease.

A simple guide to the interpretation of the significance of the association of a disease with a particular HLA allele

This review is a simple guide to the deeper meaning of the association of a disease with a particular HLA allele. We will first review some principles of the function of the adaptive immune system, and some basic notions of autoimmune disease. In this, we will focus on the tripartite unity of the Human Leukocyte Antigen (HLA)-molecule, the peptide, and the T cell receptor that recognizes the complex of peptide and HLA molecule, placing emphasis on the function of the T cell receptor. We will also touch on the evolutionary forces shaping our adaptive immune system. Then we will apply this background to some current HLA data concerning the heterogeneity of psoriatic arthritis and the extent to which it is relayed to psoriasis, to illustrate how these principles are used to advance our understanding of the disease.

Crossreactive public TCR sequences undergo positive selection in the human thymic repertoire

We investigated human T-cell repertoire formation using high throughput TCRβ CDR3 sequencing in immunodeficient mice receiving human hematopoietic stem cells (HSCs) and human thymus grafts. Replicate humanized mice generated diverse and highly divergent repertoires. Repertoire narrowing and increased CDR3β sharing was observed during thymocyte selection. While hydrophobicity analysis implicated self-peptides in positive selection of the overall repertoire, positive selection favored shorter shared sequences that had reduced hydrophobicity at positions 6 and 7 of CDR3βs, suggesting weaker interactions with self-peptides than unshared sequences, possibly allowing escape from negative selection. Sharing was similar between autologous and allogeneic thymi and occurred between different cell subsets. Shared sequences were enriched for allo-crossreactive CDR3βs and for Type 1 diabetes-associated autoreactive CDR3βs. Single-cell TCR-sequencing showed increased sharing of CDR3αs compared to CDR3βs between mice. Our data collectively implicate preferential positive selection for shared human CDR3βs that are highly cross-reactive. While previous studies suggested a role for recombination bias in producing "public" sequences in mice, our study is the first to demonstrate a role for thymic selection. Our results implicate positive selection for promiscuous TCRβ sequences that likely evade negative selection, due to their low affinity for self-ligands, in the abundance of "public" human TCRβ sequences.

Quantifying size and diversity of the human T cell alloresponse

Alloreactive T lymphocytes are the primary mediators of immune responses in transplantation, both in the graft-versus-host and host-versus-graft directions. While essentially all clones comprising the human T cell repertoire have been selected on self-peptide presented by self-human leukocyte antigens (self-HLAs), much remains to be understood about the nature of clones capable of responding to allo-HLA molecules. Quantitative tools to study these cells are critical to understand fundamental features of this important response; however, the large size and diversity of the alloreactive T cell repertoire in humans presents a great technical challenge. We have developed a high-throughput T cell receptor (TCR) sequencing approach to characterize the human alloresponse. We present a statistical method to model T cell clonal frequency distribution and quantify repertoire diversity. Using these approaches, we measured the diversity and frequency of distinct alloreactive CD4+ and CD8+ T cell populations in HLA-mismatched responder-stimulator pairs. Our findings indicate that the alloimmune repertoire is highly specific for a given pair of individuals, that most alloreactive clones circulate at low frequencies, and that a high proportion of TCRs is likely able to recognize alloantigens.

Hypercholesterolemia induces T cell expansion in humanized immune mice

Emerging data suggest that hypercholesterolemia has stimulatory effects on adaptive immunity and that these effects can promote atherosclerosis and perhaps other inflammatory diseases. However, research in this area has relied primarily on inbred strains of mice whose adaptive immune system can differ substantially from that of humans. Moreover, the genetically induced hypercholesterolemia in these models typically results in plasma cholesterol levels that are much higher than those in most humans. To overcome these obstacles, we studied human immune system-reconstituted mice (hu-mice) rendered hypercholesterolemic by treatment with adeno-associated virus 8-proprotein convertase subtilisin/kexin type 9 (AAV8-PCSK9) and a high-fat/high-cholesterol Western-type diet (WD). These mice had a high percentage of human T cells and moderate hypercholesterolemia. Compared with hu-mice that had lower plasma cholesterol, the PCSK9-WD mice developed a T cell-mediated inflammatory response in the lung and liver. Human CD4+ and CD8+ T cells bearing an effector memory phenotype were significantly elevated in the blood, spleen, and lungs of PCSK9-WD hu-mice, whereas splenic and circulating regulatory T cells were reduced. These data show that moderately high plasma cholesterol can disrupt human T cell homeostasis in vivo. This process may not only exacerbate atherosclerosis, but also contribute to T cell-mediated inflammatory diseases in the hypercholesterolemia setting.

Dual IFN-γ/hypoxia priming enhances immunosuppression of mesenchymal stromal cells through regulatory proteins and metabolic mechanisms

The immunosuppressive capacity of human mesenchymal stromal cells (MSCs) renders them promising candidates for treating diverse immune disorders. However, after hundreds of clinical trials, there are still no MSC therapies approved in the United States. MSCs require specific cues to adopt their immunosuppressive phenotype, and yet most clinical trials use cells expanded in basic culture medium and growth conditions. We propose that priming MSCs prior to administration will improve their therapeutic efficacy. Interferon-gamma (IFN-γ) priming are cues common to situations of immune escape that have individually shown promise as MSC priming cues but have not been systematically compared. Using mixed lymphocyte reactions, we show that priming MSCs with either cue alone improves T-cell inhibition. However, combining the two cues results in additive effects and markedly enhances the immunosuppressive phenotype of MSCs. We demonstrate that IFN-γ induces expression of numerous immunosuppressive proteins (IDO, PD-L1, HLA-E, HLA-G), whereas hypoxia switches MSCs to glycolysis, causing rapid glucose consumption and production of T-cell inhibitory lactate levels. Dual IFN-γ/hypoxia primed MSCs display both attributes and have even higher induction of immunosuppressive proteins over IFN-γ priming alone (IDO and HLA-G), which may reflect another benefit of metabolic reconfiguration.

Origin of Enriched Regulatory T Cells in Patients Receiving Combined Kidney-Bone Marrow Transplantation to Induce Transplantation Tolerance

We examined tolerance mechanisms in patients receiving HLA-mismatched combined kidney-bone marrow transplantation (CKBMT) that led to transient chimerism under a previously published nonmyeloablative conditioning regimen (Immune Tolerance Network study 036). Polychromatic flow cytometry and high-throughput sequencing of T cell receptor-β hypervariable regions of DNA from peripheral blood regulatory T cells (Tregs) and CD4 non-Tregs revealed marked early enrichment of Tregs (CD3⁺ CD4⁺ CD25^high CD127^low Foxp3⁺ ) in blood that resulted from peripheral proliferation (Ki67⁺ ), possibly new thymic emigration (CD31⁺ ), and, in one tolerant subject, conversion from non-Tregs. Among recovering conventional T cells, central memory CD4⁺ and CD8⁺ cells predominated. A large proportion of the T cell clones detected in posttransplantation biopsy specimens by T cell receptor sequencing were detected in the peripheral blood and were not donor-reactive. Our results suggest that enrichment of Tregs by new thymic emigration and lymphopenia-driven peripheral proliferation in the early posttransplantation period may contribute to tolerance after CKBMT. Further, most conventional T cell clones detected in immunologically quiescent posttransplantation biopsy specimens appear to be circulating cells in the microvasculature rather than infiltrating T cells.

Coronary Artery Calcification and Rheumatoid Arthritis: Lack of Relationship to Risk Alleles for Coronary Artery Disease in the General Population

OBJECTIVE

Coronary artery disease (CAD) in the general population is characterized by an increased frequency of particular susceptibility single-nucleotide polymorphisms (SNPs). Because the frequency of CAD is increased among patients with rheumatoid arthritis (RA), we sought to determine whether the frequency of these SNPs is increased in RA patients with CAD, hypothesizing that RA could enhance CAD risk by acting through established genetic pathways predisposing to CAD.

METHODS

Coronary artery calcification (CAC) as detected by computed tomography was used as a measure of CAD in 561 patients with RA. One hundred SNPs associated with CAD in the general population were genotyped or imputed, and their relationship to CAC was established through multiple regression analysis for individual SNPs and a genetic risk score representing their cumulative effect.

RESULTS

Ninety-one CAD-related SNPs were genotyped successfully; of these, 81 exhibited no association with CAC (Agatston units) or different CAC categorizations, either individually or collectively, in the genetic risk score. Only rs579459 (ABO) and rs17676451 (HAL) had a consistent positive association between genotype and CAC, with a significant increase in the frequency of the effect allele in both homozygous and heterozygous genotype distributions. Five were variably negatively associated. Furthermore, a positive association between the Disease Activity Score in 28 joints and CAC was observed, and after adjustment for traditional cardiovascular risk factors, it was not modified by correcting for the CAD-related SNP genetic risk score.

CONCLUSION

The increased risk of CAC in patients with RA does not appear to operate primarily through established genetically regulated atherogenic mechanisms that are preponderant in the general population.

Clinical and genetic associations of radiographic sacroiliitis and its different patterns in psoriatic arthritis

OBJECTIVES

We aimed to 1) identify clinical and genetic associations of sacroiliitis (SI) in patients with psoriatic arthritis (PsA), and 2) describe the different radiographic patterns of SI in PsA and their clinical and genetic associations.

METHODS

283 PsA patients, fulfilling CASPAR criteria, underwent detailed skin and rheumatologic assessments. In addition, HLA-B*27 and B*080101 status was recorded, which have been shown as the key genetic markers of radiographic SI in PsA. Grade 2 Unilateral or bilateral radiographic changes of SI were required for inclusion and involvement was further defined as asymmetrical or symmetrical.

RESULTS

70 patients (25%) had radiographic SI; all either with a present or past history of backache. Regression analysis demonstrated a significant association of SI with peripheral joint erosions (p=0.043), PASI maximum (p=0.041), younger age of PsA onset (p=<0.001), presence of HLA-B*0801 (p=0.002) and only marginal significance with HLA-B*2705 (p=0.059). Asymmetrical SI was noted in 51 patients (73%). In striking contrast to those patients with symmetrical SI, patients with asymmetrical SI were more likely to be female (p=0.04), have a trend towards more severe nail disease (p=0.08) and peripheral joint erosions (p=0.08), more osteolysis (p=0.01), more HLA-B*0801 positivity (p=0.001) and much less HLA-B*270502 positivity (p=<0.001).

CONCLUSIONS

PsA developing at a younger age, severe skin disease, peripheral joint erosions, and HLA-B*0801 are significantly associated with SI, and there was only a marginal trend towards significance for HLA-B*2705. HLA-B*27 positive Axial-PsA patients resemble AS, while HLA-B*0801 positive Axial-PsA patients have asymmetrical and/or unilateral SI, which are typical of PsA.

Axial Disease in Psoriatic Arthritis study: defining the clinical and radiographic phenotype of psoriatic spondyloarthritis

Objectives

To compare the prevalence, clinical and radiographic characteristics of psoriatic spondyloarthritis (PsSpA) in psoriatic arthritis (PsA), with ankylosing spondylitis (AS).

Methods

A prospective single-centre cross-sectional observational study recruited consecutive PsA and AS cases. Participants completed outcome measures, and underwent clinical examination, axial radiographic scoring and HLA-sequencing. Multivariable analyses are presented.

Results

The 402 enrolled cases (201 PsA, 201 AS; fulfilling classification criteria for respective conditions) were reclassified based upon radiographic axial disease and psoriasis, as: 118 PsSpA, 127 peripheral-only PsA (pPsA), and 157 AS without psoriasis (AS) cases. A significant proportion of patients with radiographic axial disease had PsSpA (118/275; 42.91%), and often had symptomatically silent axial disease (30/118; 25.42%). Modified New York criteria for AS were fulfilled by 48/201 (23.88%) PsA cases, and Classification of Psoriatic Arthritis criteria by 49/201 (24.38%) AS cases. pPsA compared with PsSpA cases had a lower frequency of HLA-B*27 (OR 0.12; 95% CI 0.05 to 0.25). Disease activity, metrology and disability were comparable in PsSpA and AS. A significant proportion of PsSpA cases had spondylitis without sacroiliitis (39/118; 33.05%); they less frequently carried HLA-B*27 (OR 0.11; 95% CI 0.04 to 0.33). Sacroiliac joint complete ankylosis (adjusted OR, OR_adj 2.96; 95% CI 1.42 to 6.15) and bridging syndesmophytes (OR_adj 2.78; 95% CI 1.49 to 5.18) were more likely in AS than PsSpA. Radiographic axial disease was more severe in AS than PsSpA (Psoriatic Arthritis Spondylitis Radiology Index Score: adjusted incidence risk ratio 1.13; 95% CI 1.09 to 1.19).

Conclusions

In a combined cohort of patients with either PsA or AS from a single centre, 24% fulfilled classification criteria for both conditions. The pattern of axial disease was influenced significantly by the presence of skin psoriasis and HLA-B*27.

Association of Elevations of Specific T Cell and Monocyte Subpopulations in Rheumatoid Arthritis With Subclinical Coronary Artery Atherosclerosis

OBJECTIVE

Coronary artery disease (CAD) is the leading cause of excess deaths in rheumatoid arthritis (RA). However, identification of features denoting patients with a risk of developing CAD is lacking. The composition of circulating peripheral blood mononuclear cell (PBMC) subsets in RA patients differs markedly from that in healthy controls with regard to the extent of T cell activation, with clonal expansion and differentiation to effector memory status, and presence of inflammatory monocytes. In this study, we sought to evaluate whether elevations in these PBMC subpopulations in RA patients could denote those with an increased risk of subclinical CAD, as determined by the presence of coronary artery calcification (CAC).

METHODS

The study cohort comprised 72 patients with RA who underwent cardiac computed tomography to assess CAC. PBMC subsets were determined by multiparameter flow cytometry. Multivariable logistic regression was used to determine the associations between PBMC subpopulations and the presence of CAC.

RESULTS

Among the 72 patients with RA, 33% had CAC and exhibited significant increases in the levels of circulating CD4 T cell subsets denoting activation and differentiation to the effector memory phenotypes. Analogous increases in the levels of CD8 T cell subsets, as well as in the CD14(high)CD16+ intermediate monocyte subset, were also present in these patients, as compared to those without CAC. The increases in the CD4 and CD8 T cell subsets were highly intercorrelated, whereas the increases in CD14(high)CD16+ monocytes were independent of elevations in the CD4 T cell subsets. After adjustments for relevant confounders, the levels of CD4+CD56+CD57+ T cells and CD14(high)CD16+ monocytes remained associated with the presence of CAC.

CONCLUSION

These findings indicate that PBMC subsets are markers for the presence of CAC and suggest that mechanisms of atherogenesis in RA may operate in part through the elevations in these subsets, raising further questions about the mechanisms underlying the presence of such alterations in cell composition in patients with RA and the potential for shared etiologic pathways between RA and cardiovascular disease.

Certain class I HLA alleles and haplotypes implicated in susceptibility play a role in determining specific features of the psoriatic arthritis phenotype

OBJECTIVES

Psoriatic arthritis (PsA) susceptibility is associated with several different class I alleles, suggesting separate patterns of MHC effect. This exploratory study was based on the hypothesis that heterogeneity of the clinical phenotype of PsA might be explained by differing associations of clinical features with these susceptibility genes.

METHODS

The clinical phenotype of 282 PsA patients in a cohort previously studied for associations with human leukocyte antigen (HLA)-B and HLA-C genotypes was first preliminarily assessed by univariate associations of susceptibility genes with specific clinical characteristics. To explore the potential genotypic effects of pairwise combinations of different HLA-B and C alleles/haplotypes, we created a series of allele/haplotype risk scores combining single alleles/haplotypes separately associated with being in the highest PsA severity propensity tertile based on the features studied by univariate analysis.

RESULTS

In exploratory univariate analyses, B*27:05:02 was positively associated with enthesitis, dactylitis and symmetric sacroiliitis, whereas B*08:01:01-C*07:01:01and its component alleles were positively associated with joint fusion and deformities, asymmetrical sacroiliitis, and dactylitis. HLA-C*06:02:01 was negatively associated with asymmetrical sacroiliitis. The highest propensity score for severe PsA was with B*27:05:02-C*02:02:02, B*08:01:01-C*07:01:01 and B*37:01:01-C*06:02:01, but not the B*27:05:02-C*01:01:01 or B*57:01:01-C*06:02:01 haplotypes. In contrast, B*44 haplotypes were associated with presence of milder disease, and in univariate analysis with a decreased frequency of enthesitis, joint fusion, deformities and dactylitis.

CONCLUSIONS

Different HLA susceptibility genes were associated with particular features that defined the PsA phenotype of a given patient. Additive interactions between different susceptibility HLA alleles defined the propensity for a more severe or milder musculoskeletal phenotype.

Association of fine specificity and repertoire expansion of anticitrullinated peptide antibodies with rheumatoid arthritis associated interstitial lung disease

BACKGROUND

Interstitial lung disease (ILD) is associated with high morbidity and mortality in rheumatoid arthritis (RA). Citrullinated proteins are observed in RA lung tissues; however, the association of specific anticitrullinated peptide antibodies (ACPA) with ILD in RA is unknown.

METHODS

RA patients underwent multidetector CT (MDCT) of the chest, from which ILD features and a semiquantitative ILD Score (ILDS; range 0-32) were assessed. Anti-CCP (CCP2) and levels of a panel of antibodies against 17 citrullinated and four non-citrullinated peptides were assessed from concurrent serum samples using a custom Bio-Plex bead array. High level ACPA was defined as ≥the group 75th percentile.

RESULTS

Among the 177 RA patients studied, median levels of CCP2 and all specific ACPAs were 46-273% higher among RA patients with versus those without ILD (all p values <0.05), and higher levels correlated with higher ILDS. In contrast, levels of non-citrullinated protein antibodies were not higher in those with ILD. RA patients had a median of 2 high level ACPA reactivities (range 0-16), with each high level ACPA associated, on average, with a 0.10 unit higher ILDS (p=0.001). This association remained significant after adjusting for characteristics associated with ILD (age, gender, current and former smoking, Disease Activity Score for 28 joints, current prednisone and leflunomide use). More high level ACPA were observed in those with versus without pulmonary function restriction or impaired diffusion.

CONCLUSIONS

Our findings of a broader ACPA repertoire in RA ILD suggest a possible role for ACPA in the pathogenesis of ILD.

Immunologic characteristics of intrarenal T cells: trafficking of expanded CD8+ T cell β-chain clonotypes in progressive lupus nephritis

OBJECTIVE

To better define the immunologic character of the T cell infiltrate in lupus nephritis.

METHODS

We performed double immunohistochemical staining and clonotypic T cell receptor (TCR) β-chain sequencing in multiple anatomic regions isolated by laser-capture microdissection from renal biopsy samples.

RESULTS

Systemic lupus erythematosus (SLE) kidneys have a variably patterned and often extensive infiltrate of predominantly clonally expanded T cells of CD4 and CD8 lineages. CD4+ T cells were prominent in nearly two-thirds of SLE biopsy samples and were distributed as broad periglomerular aggregates or intermixed with CD8+ T cells forming periglomerular caps. Sequencing of the TCR from periglomerular regions showed a predominance of clonally expanded T cells. The CD8+ T cells, which were present in all biopsy samples, often adhered to Bowman's capsule and infiltrated the tubular epithelium. They exhibited features that suggest participation in an adaptive immune response: differentiation into CD28(null) memory-effector phenotype, trafficking of the same expanded clonotype to different regions of the kidney and to the peripheral blood, and clonal persistence for years in repeat biopsy samples. CD8+ T cell tubulitis was especially associated with progressive changes.

CONCLUSION

The immunologic characteristics of the infiltrating CD4+ and CD8+ T cells in the lupus kidney indicate that they have the potential to mediate injury, which may be relevant to development of progressive renal failure. Whereas the oligoclonality of the CD4+ T cell infiltrate is consistent with the paradigm of SLE as a class II major histocompatibility complex-associated autoimmune disease, the finding of CD8+ T cell clonality and trafficking implies participation in a distinct systemic adaptive immune response.

A model for personalized in vivo analysis of human immune responsiveness

Studies of human immune diseases are generally limited to the analysis of peripheral blood lymphocytes of heterogeneous patient populations. Improved models are needed to allow analysis of fundamental immunologic abnormalities predisposing to disease and in which to assess immunotherapies. Immunodeficient mice receiving human fetal thymus grafts and fetal CD34(+) cells intravenously produce robust human immune systems, allowing analysis of human T cell development and function. However, to use humanized mice to study human immune-mediated disorders, immune systems must be generated from adult hematopoietic cells. Here, we demonstrated robust immune reconstitution in mice with hematopoietic stem cells (HSCs) aspirated from bone marrow of adults with type 1 diabetes (T1D) and healthy control volunteers. In these humanized mice, cryopreservation of human leukocyte antigen allele-matched fetal thymic tissue prevented allogeneic adult HSC rejection. Newly generated T cells, which included regulatory T cells (T(regs)), were functional and self-tolerant and had a diverse repertoire. The immune recognition of these mice mimicked that of the adult CD34(+) cell donor, but the T cell phenotypes were more predominantly "naïve" than those of the adult donors. HSCs from T1D and control donors generated similar numbers of natural T(regs) intrathymically; however, peripheral T cells from T1D subjects showed increased proportions of activated or memory cells compared to controls, suggesting possible HSC-intrinsic differences in T cell homeostasis that might underlie immune pathology in T1D. This "personalized immune" mouse provides a new model for individualized analysis of human immune responses that may provide new insights into not only T1D but also other forms of immune function and dysfunction as well.

HLA associations reveal genetic heterogeneity in psoriatic arthritis and in the psoriasis phenotype

OBJECTIVE

Rigorously ascertained cases of psoriatic arthritis in subjects presenting to a rheumatology unit were compared with cases of psoriasis in subjects presenting to a dermatology unit, where subjects with musculoskeletal features were excluded, to address 1) the extent to which the contribution of the major histocompatibility complex (MHC) to psoriatic arthritis susceptibility resembles that in psoriasis, and 2) whether MHC genes determine quantitative traits within the psoriatic arthritis phenotype.

METHODS

Separate discovery and validation subcohorts of patients recruited from a relatively homogeneous population were studied by sequence-based HLA typing, in which frequencies of the HLA-B and HLA-C alleles and haplotypes were compared.

RESULTS

In patients with psoriatic arthritis, the frequency of C*06:02 was lower than that in patients with psoriasis (28.7% versus 57.5%; P = 9.9 × 10(-12) ). Three haplotypes containing B*27:05 or B*39:01 were significantly increased in frequency in patients with psoriatic arthritis, but not in those with psoriasis. The structurally related B*39:06 allele was not increased in frequency. B*27 was associated with an interval of 0.98 years between skin and musculoskeletal disease (P = 2.05 × 10(-6) ), compared with an interval of 10.14 years for C*06. Preliminary evidence suggested that B*38:01 and B*08 may be associated with psoriatic arthritis susceptibility, and that allotypes encoding P2 pockets that bind side chains opposite in charge from those encoded by the B*27 and B*39 molecules may exert a protective role.

CONCLUSION

These findings suggest that the psoriasis phenotype results from two patterns of MHC effect. The first involves the classic psoriasis susceptibility gene C*06, which confers more penetrant skin disease with less prevalent and more time-dependent musculoskeletal phenotype development. The second pattern appears to be mediated by HLA-B alleles, notably B*27, and includes temporally more coincident musculoskeletal involvement that is nearly equivalent in penetrance to that of the skin disease.

Circulating activated and effector memory T cells are associated with calcification and clonal expansions in bicuspid and tricuspid valves of calcific aortic stenosis

We sought to delineate further the immunological significance of T lymphocytes infiltrating the valve leaflets in calcific aortic stenosis (CAS) and determine whether there were associated alterations in circulating T cells. Using clonotypic TCR β-chain length and sequence analysis we confirmed that the repertoire of tricuspid CAS valves contains numerous expanded T cell clones with varying degrees of additional polyclonality, which was greatest in cases with severe calcification. We now report a similar proportion of clonal expansions in the much younger bicuspid valve CAS cases. Peripheral blood flow cytometry revealed elevations in HLA-DR(+) activated CD8 cells and in the CD8(+)CD28(null)CD57(+) memory-effector subset that were significantly greater in both bicuspid and tricuspid CAS cases with more severe valve calcification. Lesser increases of CD4(+)CD28(null) T cells were identified, principally in cases with concurrent atherosclerotic disease. Upon immunostaining the CD8 T cells in all valves were mainly CD28(null), and CD8 T cell percentages were greatest in valves with oligoclonal repertoires. T cell clones identified by their clonotypic sequence as expanded in the valve were also found expanded in the circulating blood CD28(null)CD8(+) T cells and to a lesser degree in the CD8(+)CD28(+) subset, directly supporting the relationship between immunologic events in the blood and the valve. The results suggest that an ongoing systemic adaptive immune response is occurring in cases with bicuspid and tricuspid CAS, involving circulating CD8 T cell activation, clonal expansion, and differentiation to a memory-effector phenotype, with trafficking of T cells in expanded clones between blood and the valve.

KIR-HLA and maternal-infant HIV-1 transmission in sub-Saharan Africa

Numerous studies have suggested a role for natural killer (NK) cells in attenuation of HIV-1 disease progression via recognition by killer-cell immunoglobulin-like receptors (KIRs) of specific HLA class I molecules. The role of KIR and HLA class I has not been addressed in the context of maternal-infant HIV-1 transmission. KIR and HLA class I B and C genes from 224 HIV-1-infected mothers and 222 infants (72 infected and 150 uninfected) from South Africa were characterized. Although a number of significant associations were determined in both the total group and in the nevirapine (NVP) exposed group, the most significant findings involved KIR2DL2 and KIR2DL3 and HLA-C. KIR2DL2/KIR2DL3 was underrepresented in intrapartum (IP)-transmitting mothers compared to non-transmitting (NT) mothers (P = 0.008) and remained significant (P = 0.036) after correction for maternal viral load (MVL). Homozygosity for KIR2DL3 alone and in combination with HLA-C allotype heterozygosity (C1C2) was elevated in IP-transmitting mothers compared to NT mothers (P = 0.034 and P = 0.01 respectively), and after MVL correction (P = 0.033 and P = 0.027, respectively). In infants, KIR2DL3 in combination with its HLA-C1 ligand (C1) as well as homozygosity for KIR2DL3 with C1C2, were both found to be underrepresented in infected infants compared to exposed uninfected infants in the total group (P = 0.06 and P = 0.038, respectively) and in the sub-group of infants whose mothers received NVP (P = 0.007 and P = 0.03, respectively). These associations were stronger post MVL adjustment (total group: P = 0.02 and P = 0.009, respectively; NVP group: P = 0.004 and P = 0.02, respectively). Upon stratification according to low and high MVL, all significant associations fell within the low MVL group, suggesting that with low viral load, the effects of genotype can be more easily detected. In conclusion this study has identified a number of significant associations that suggest an important role for NK cells in maternal-to-infant HIV-1 transmission.

Psoriatic arthritis: from pathogenesis to therapy

Psoriatic arthritis is a multigenic autoimmune disease that involves synovial tissue, entheseal sites and skin, and that may result in significant joint damage. Although there are no diagnostic tests for psoriatic arthritis, research has identified consistent features that help to distinguish the condition from other common rheumatic diseases. Comparison of HLA-B and HLA-C regions in psoriatic arthritis with those in psoriasis without joint involvement demonstrates significant differences, such that psoriatic arthritis cannot be viewed simply as a subset of genetically homogeneous psoriasis. T-cell receptor phenotypic studies have failed to identify antigen-driven clones, and an alternative hypothesis for CD8 stimulation involving innate immune signals is proposed. Finally, imaging studies have highlighted entheseal involvement in psoriatic arthritis, and it is possible that entheseal-derived antigens may trigger an immune response that is critically involved in disease pathogenesis.

Description of two new HLA-C alleles in a black South African population

Two new HLA-C alleles, Cw*0333 and Cw*0217, were identified in a Black South African population. HLA-Cw*0333 differs from Cw*030201 by an A-->G substitution at nucleotide 323, yielding an unusual missense substitution of Cys for the conserved Tyr-84 at the antigen cleft terminus. Molecular modeling suggests that this alters the predicted interactions of this critical residue with the opposite alpha(2)-helix, the peptide COOH terminus and possibly KIR2DL2. The second allele, Cw*0217, differs from Cw*0205 by an A-->T substitution at nucleotide 368, resulting in a Tyr-->Phe substitution at residue 99 of the HLA-C beta-pleated sheet that likely influences peptide side-chain binding. Both Cw*0333 and Cw*0217 appear to have arisen by missense mutations, respectively, from the HLA-B*5801-Cw*0302 and B*080101-Cw*0205 haplotypes.

The lymphocytic infiltration in calcific aortic stenosis predominantly consists of clonally expanded T cells

Valve lesions in degenerative calcific aortic stenosis (CAS), a disorder affecting 3% of those older than 75 years, are infiltrated by T lymphocytes. We sought to determine whether the alphabeta TCR repertoire of these valve-infiltrating lymphocytes exhibited features either of a polyclonal nonselective response to inflammation or contained expanded clones suggesting a more specific immune process. TCR beta-chain CDR3-length distribution analysis using PCR primers specific for 23 Vbeta families performed in eight individuals with CAS affecting tri- or bileaflet aortic valves revealed considerable oligoclonal T cell expansion. In five cases, beta-chain nucleotide sequencing in five selected Vbeta families showed that an average of 92% of the valve-infiltrating T cell repertoire consisted of expanded T cell clones, differing markedly in composition from the relatively more polyclonal peripheral CD8 or CD4 T cell subsets found even in this elderly population. Twenty-four of the valve-infiltrating T cell clones also had the same clone identified in blood, some of which were highly expanded. Interestingly, 22 of these 24 shared clones were CD8 in lineage (p = 1.5 x 10(-12)), suggesting a possible relationship to the expanded CD8(+)CD28(-) T cell clones frequently present in the elderly. Additionally, the sequences of several TCR beta-chain CDR3 regions were homologous to TCR beta-chains identified previously in allograft arteriosclerosis. We infer that these findings are inconsistent with a nonselective secondary response of T cells to inflammation and instead suggest that clonally expanded alphabeta T cells are implicated in mediating a component of the valvular injury responsible for CAS.

Reshaping Cinderella's slipper: the shared epitope hypothesis

This issue of Arthritis Research and Therapy contains a succinct and elegant paper by Michou and colleagues that advances our understanding of the genetic basis of rheumatoid arthritis (RA) by reclassifying the contribution of RA susceptibility alleles according to their structure. This line of research is potentially important in our conceptualization of the mechanism of disease in RA, in predicting disease course and severity, and as a model for further studies on this topic. The author's approach to reassessing the molecular structure of the shared epitope redirects attention to using the binding properties of the major histocompatibility complex molecules associated with susceptibility to search for the peptides driving the autoimmune process underlying rheumatoid arthritis.

An affinity/avidity model of peripheral T cell regulation

We show in these studies that Qa-1-dependent CD8+ T cells are involved in the establishment and maintenance of peripheral self tolerance as well as facilitating affinity maturation of CD4+ T cells responding to foreign antigen. We provide experimental evidence that the strategy used by the Qa-1-dependent CD8+ T cells to accomplish both these tasks in vivo is to selectively downregulate T cell clones that respond to both self and foreign antigens with intermediate, not high or low, affinity/avidity. Thus, the immune system evolved to regulate peripheral immunity using a unified mechanism that efficiently and effectively permits the system to safeguard peripheral self tolerance yet promote the capacity to deal with foreign invaders.

The molecular pathophysiology of subacromial bursitis in rotator cuff disease

Little information exists on the molecular and biochemical pathophysiology of subacromial bursitis and rotator cuff disease. We investigated the pattern of expression of cytokines (interleukin [IL]-1beta, IL-1, IL-6, tumor necrosis factor [TNF] alpha, small inducible cytokines), metalloproteases, and cyclooxygenases in the subacromial bursa in patients with rotator cuff disease. Subacromial bursa specimens were prepared for molecular and biochemical analysis in patients undergoing shoulder surgery following an institutional review board-approved protocol. Specimens were analyzed for the presence of cytokines, metalloproteases, and cyclooxygenases by use of microarray for gene expression and immunohistocytochemistry. Microarray analysis for gene expression and immunohistochemistry demonstrated that the expression of several cytokine genes (TNF, IL-1alpha, IL-1beta, and IL-6) was increased in patients with subacromial bursitis compared with control specimens. Furthermore, the expression of metalloproteases (MMP-1 and MMP-9) and cyclooxygenases (COX-1 and COX-2) in the bursitis group was found to be increased as compared with controls. Although further investigation is required, these studies suggest that inflammation of the subacromial bursa does occur in patients with rotator cuff disease. These findings support the role of anti-inflammatory agents in the treatment of subacromial impingement and emphasize the importance of subacromial bursectomy to reduce inflammation in rotator cuff disease.

Relationship of HLA-DQ8 and severity of celiac disease: comparison of New York and Parisian cohorts

BACKGROUND & AIMS

Celiac disease is a polygenic disorder associated with HLA-DQ2 or HLA-DQ8, which are present in greater than 90% of patients. The disease is considered milder in the United States compared with Europe. We assessed whether differences in the frequency of HLA type may account for differences in severity of the disease by using cohorts of patients from New York and Paris.

METHODS

HLA-DQ typing was performed on patients with celiac disease in New York and Paris. Clinical and pathologic data were compared between the New York and Parisian cohorts and also correlated with the different HLA types (HLA-DQ2, HLA-DQ2/-DQ8, HLA-DQ8).

RESULTS

Among these patients, the disease was milder in the New York cohort compared with the Parisian cohort. There were fewer patients with a classical presentation (45% and 89%, respectively; P < 0.001) and less severe pathology (total villous atrophy, 64% and 89%, respectively; P < 0.05), and less marked intraepithelial lymphocytosis (intraepithelial leukocytes [IELs]/100 enterocytes, 48.1 and 82.5, respectively; P < 0.0001). HLA-DQ2 homozygotes were less prevalent in the New York cohort compared with the Parisian cohort (59% and 79%, respectively; P = 0.08). HLA-DQ8 alleles were more prevalent in the New York cohort compared with the Parisian cohort (41% and 21%, respectively; P = 0.026). There was, however, no difference in the clinical or pathologic parameters of severity when we compared the groups based on HLA type.

CONCLUSIONS

HLA-DQ8 alleles were increased in the New York cohort of patients with celiac disease; however, this did not account for less severe manifestations of the disease.

Mother-to-Child Transmission of HIV-1: Strong Association With Certain Maternal HLA-B Alleles Independent of Viral Load Implicates Innate Immune Mechanisms

The transmission of HIV-1 from mother to child during pregnancy is unlike other types of HIV-1 transmission because the child shares major histocompatibility complex (MHC) genes with the mother during a time while the mother is induced to tolerate the paternally derived fetal MHC molecules, in part through natural killer (NK) recognition of MHC polymorphisms. The relevance of these immune mechanisms to HIV-1 transmission was assessed by determining the HLA-B alleles of mother and infant. Almost half (48%) of mothers who transmitted with low viral loads had HLA-B*1302, B*3501, B*3503, B*4402, or B*5001 alleles, compared with 8% of nontransmitting mothers (P=0.001). Conversely, 25% of mothers who did not transmit despite high viral loads had B*4901 and B*5301, vs. 5% of transmitting mothers (P=0.003), a pattern of allelic involvement distinct from that influencing HIV-1 infection outcome. The infant's HLA-B alleles did not appear associated with transmission risk. The HLA-B*4901 and B*5301 alleles that were protective in the mother both differed respectively from the otherwise identical susceptibility alleles, B*5001 and B*3501, by 5 amino acids encoding the ligand for the KIR3DL1 NK receptor. These results suggest that the probable molecular basis of the observed association involves definition of the maternal NK recognition repertoire by engagement of NK receptors with polymorphic ligands encoded by maternal HLA-B alleles, and that the placenta is the likely site of the effect that appears to protect against transmission of maternal HIV-1 through interrelating adaptive and innate immune recognition.