Incomplete thymic involution in systemic sclerosis and rheumatoid arthritis

Activation of gp130 signaling in T cells drives TH17-mediated multi-organ autoimmunity

The IL-6-gp130-STAT3 signaling axis is a major regulator of inflammation. Activating mutations in the gene encoding gp130 and germline gain-of-function mutations in STAT3 (STAT3GOF) are associated with multi-organ autoimmunity, severe morbidity, and adverse prognosis. To dissect crucial cellular subsets and disease biology involved in activated gp130 signaling, the gp130-JAK-STAT3 axis was constitutively activated using a transgene, L-gp130, specifically targeted to T cells. Activating gp130 signaling in T cells in vivo resulted in fatal, early onset, multi-organ autoimmunity in mice that resembled human STAT3GOF disease. Female mice had more rapid disease progression than male mice. On a cellular level, gp130 signaling induced the activation and effector cell differentiation of T cells, promoted the expansion of T helper type 17 (TH17) cells, and impaired the activity of regulatory T cells. Transcriptomic profiling of CD4+ and CD8+ T cells from these mice revealed commonly dysregulated genes and a gene signature that, when applied to human transcriptomic data, improved the segregation of patients with transcriptionally diverse STAT3GOF mutations from healthy controls. The findings demonstrate that increased gp130-STAT3 signaling leads to TH17-driven autoimmunity that phenotypically resembles human STAT3GOF disease.

Thymus variants on imaging of patients with primary Sjögren's syndrome and polymyositis/dermatomyositis: clinical and immunological significance

We investigated the presence of radiographic thymus variants using a scoring system and examined their association with clinical and immunological features in primary Sjögren's syndrome (pSS) and polymyositis/dermatomyositis (PM/DM) patients. Cases of 72 patients with pSS and 47 with PM/DM were randomly selected from all visitors to our department who received chest CT scanning, excluding those with thymoma or thymic cyst, or age <30 years. We quantitatively interpreted and assessed thymus size and attenuation score in axial CT images. Thymic enlargement was identified in 16 (22.2%) pSS and 14 (29.8%) PM/DM patients. A thymus attenuation score ≥ 2 was seen in 11 (15.3%) pSS and 9 (19.1%) PM/DM patients. Thymic enlargement showed a significant association with the titre of rheumatoid factor in PM/DM patients. Thymic enlargement and score showed a significant association with body weight in pSS patients. Radiographic thymus variants are often observed in pSS and PM/DM patients, particularly in cases of PM/DM, and may suggest the role of an abnormal immune response in their pathogenesis.

Thymus variants on imaging in patients with rheumatoid arthritis-Clinical and immunological significance

OBJECTIVES

We sought to clarify the presence of radiographic thymus variants using a scoring system, and their association with clinical and immunological features in RA patients.

METHODS

387 RA patients randomly selected from all patients visiting our department who underwent chest CT scanning, with exclusion of patients with thymoma or thymic cyst, or age < 30 y. Thymus size and attenuation score in axial CT images were quantitatively interpreted and assessed. Associations between immunophenotype data and clinical and serological features were analysed in a subset of patients.

RESULTS

Thymic enlargement was found in 76 (19.6%) patients, and a thymus attenuation score ≥ 2 was found in 50 (12.9%) patients. The score was significantly associated with antibodies to citrullinated peptide antigens (ACPA) positivity. Thymic enlargement was significantly associated with the proportions of CD4+ effector memory T cells.

CONCLUSION

Radiographic thymus variants were frequently observed in RA patients, and may reflect an abnormal immune response involved in the pathogenesis of RA.

Imiquimod-induced dermatitis impairs thymic tolerance of autoreactive CD4+ T cells to desmoglein 3

BACKGROUND

The thymus plays an essential role in removing autoreactive T cells. Autoantigen-expressing thymic epithelial cells (TECs) contribute to the tolerogenic process. The thymus transiently shrinks as an acute thymic involution (ATI) under various inflammatory conditions. However, whether ATI occurs during local skin inflammation remains unclear, as does its influence on thymic immune tolerance.

OBJECTIVE

We investigated whether imiquimod-induced dermatitis causes ATI and impairs thymic immune tolerance against desmoglein 3 (Dsg3), an epidermal autoantigen of pemphigus vulgaris.

METHODS

5% imiquimod cream was applied daily, at 62.5 mg/day (high dose group) or 31.25 mg/day (low dose group), for 1 week on the back of wild-type mice, and to wild-type mice that had undergone bone-marrow transplantation from Dsg3-specific T-cell receptor (TCR) transgenic-Rag2^-/- mice. Next, thymocytes, TECs and other immune cells were analyzed by flow cytometry. TEC-associated Dsg3 expression was also analyzed by immunofluorescence staining.

RESULTS

Thymus weight and thymocyte number in all developmental stages decreased in a dose-dependent manner under imiquimod-induced dermatitis. The number of total TECs, specifically medullary, but not cortical, TECs, decreased in high and low dose groups. Accordingly, the number of Dsg3-experssing UEA-1⁺keratin 5⁺mTEC decreased in the thymus during imiquimod-induced dermatitis. Although Dsg3-sepcific transgenic thymocytes was usually deleted in the thymus under physiological condition by central tolerance, Dsg3-sepcific transgenic CD4⁺CD8^- thymocytes significantly increased in number under imiquimod-induced dermatitis.

CONCLUSION

These findings indicate a crosstalk between skin and thymus in adult mice and suggest that skin inflammation may impair thymic tolerance to autoantigens, such as Dsg3.

[Morphology of the thymus and the specific features of its cellular composition in experimental acute and chronic ulcerative colitis]

OBJECTIVE

To investigate morphological changes in the thymus, the subpopulation composition of lymphocytes and its non-lymphoid cells in dextran-induced experimental acute ulcerative colitis and in different periods of chronic ulcerative colitis.

MATERIAL AND METHODS

Acute and chronic ulcerative colitis was simulated in C57BL/6 mice, by replacing drinking water with a 1% aqueous dextran sulfate sodium solution. Thymic changes were morphometrically assessed; the number and absolute area of thymic corpuscles and epithelial cells were calculated; and the subpopulation composition of lymphocytes and thymic stromal cells was determined using flow cytofluorimetry; the Kruskal-Wallis test and the Mann-Whitney test were used to compare the groups.

RESULTS

In acute catarrhal and ulcerative colitis, there was acute accidental thymic involution with devastation of the cortical substance and with a decline in its volume fraction, with an increase in the levels of cells dying through the mechanism of apoptosis, and with a decrease in the absolute number of lymphocytes, T-helper cells, cytotoxic T-cells, regulatory T-lymphocytes, B-lymphocytes, and dendritic cells, with a rise in the index of the area of thymic corpuscles and in the content of late-phase corpuscles among them, and with the appearance of thymic corpuscles as cyst-like cavities. In chronic ulcerative colitis, the cortex was expanded and the area of thymic corpuscles and the count of medullary epithelial cells increased. The cyst-like thymic corpuscles formed clusters, the count of dendritic cells increased in early-stage chronic ulcerative colitis, but the levels of macrophages decreased in both periods of its development.

CONCLUSION

There is acute accidental involution and thymic hyperplasia with an increase in medullary epithelial cells and thymic corpuscles consisting of cytokeratin 19⁺ in the epithelial cells in experimental acute and chronic ulcerative colitis, respectively. The more pronounced epithelial cell response found in end-stage experimental chronic ulcerative colitis reflects the enhanced differentiation of regulatory T-lymphocytes and the larger number of which is observed in peripheral blood and in the focus of inflammation in patients with ulcerative colitis, according to the literature.

Th1 Biased Progressive Autoimmunity in Aged Aire-Deficient Mice Accelerated Thymic Epithelial Cell Senescence

Although autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus, are frequently associated with premature aging of the thymus, a direct link is missing between autoimmunity and thymic atrophy. Here we monitored the progression of thymic involution in Aire-deficient mice, in which defective negative selection causes spontaneous and progressive development of autoimmunity. In young and middle-aged mice, Aire deficiency appeared to be protective as supported by the reduced β-gal⁺ epithelial cells and the enhanced thymic output. However, once the autoimmune phenotype was fully developed in aged Aire-deficient mice, their thymuses underwent accelerated involution. In comparison to the age-matched wildtype littermates, old Aire-deficient mice showed lower numbers of total thymocytes and recent thymic emigrants but more β-gal⁺ thymic epithelial cells. This phenomenon may partly be attributable to the increased number of activated Th1 cells homing to the thymus. This speculation was further supported by the enhanced thymic aging following repeated challenges with complete Freund’s adjuvant immunization. Taken together, the present study highlights a unique mechanism by which autoimmunity facilitates the senescence of thymic epithelial cells through returning Th1 cells.

Reduced T-Cell Thymic Export Reflected by sj-TREC in Patients with Coronary Artery Disease

AIM

Immunologic dysfunction was recently found to be one of the most important mechanisms underlying the initiation and development of atherosclerosis. Thymus involution can contribute to immune disturbance and disequilibrium of T-cell subsets. This study aimed to explore whether recent thymic emigration (RTE) is impaired in patients with coronary artery disease (CAD).

METHODS

Content of signal-joint T cell receptor excision circles (sj-TREC) in T lymphocytes, a molecular marker of RTE, was assessed among CAD patients and age-matched controls. Monochrome multiplex quantitative PCR method was used to assess the samples' telomere length in order to exclude the potential influence of T cell proliferation on the dilution of sj-TREC. Patients were grouped according to Gensini score (GS) (low, GS ＜18; intermediate, GS 18-41; high, GS ＞41). Ordinary logistic regression models were used to determine potential risk factors for CAD and GS tertiles.

RESULTS

Average copy numbers of sj-TREC per 10(6) T lymphocytes among patients with unstable angina, stable angina, and controls were 726±429, 1213±465, and 1795±838, respectively (P＜0.001). However, there was no significant difference in telomere length among groups. Moreover, the content of sj-TREC in the high GS group was most significantly reduced than the low GS group (P＜0.001). Multivariate logistic regression analysis revealed that lower sj-TREC was independently associated with the progression of CAD (OR=0.44, P＜0.001) and higher GS (OR=0.4, P＜0.001).

CONCLUSION

Impaired RTE could be partly responsible for CAD development. Mechanisms may be involved in the disturbance of T lymphocyte compartment and interruption of maintained immune tolerance resulting from thymus involution.

Fetal programming and systemic sclerosis

OBJECTIVE

This study investigated whether birthweight is linked to an increased risk of the development of systemic sclerosis.

STUDY DESIGN

This was a multicenter case-control study with perinatal data that were obtained from 332 cases with systemic sclerosis and 243 control subjects. Birthweight was treated as a dichotomous variable (<2500 g vs ≥2500 g); low birthweight was defined as a weight <2500 g; small for gestational age was defined as birthweight <10th percentile for gestational age adjusted for sex. The relationship between systemic sclerosis and both low birthweight and small for gestational age was expressed with the crude (univariate analysis) and adjusted (multivariate analysis) odds ratio (OR).

RESULTS

Significantly increased ORs were observed in the univariate analysis for low birthweight (OR, 2.59; 95% confidence interval [CI], 1.39-5.05) and small for gestational age (OR, 2.60; 95% CI, 1.34-5.32) subjects. Similarly increased risks were confirmed for both conditions in the multivariate analysis (OR, 3.93; 95% CI, 1.92-8.07; and OR, 2.58; 95% CI, 1.28-5.19), respectively.

CONCLUSION

Low birthweight and small for gestational age at birth are risk factors for the adult onset of systemic sclerosis.

Systemic sclerosis: Recent insights

Systemic sclerosis is an orphan connective tissue disease characterized by alterations of the microvasculature, disturbances of the immune system and massive deposition of collagen and other matrix substances in the skin and internal organs. A major achievement of the recent years has been the validation of new classification criteria, allowing earlier diagnosis and earlier treatment of systemic sclerosis, before irreversible fibrosis and organ damage appeared ("window of opportunity"). Raynaud's phenomenon is usually the first sign of the disease and is considered as the main sentinel sign for the identification of very early systemic sclerosis. Systemic sclerosis is clinically heterogeneous and disease course remains unpredictable. Its prognosis depends on cardiopulmonary involvement and recent studies aim to identify serum or genetic biomarkers predictive of severe organ involvement. Moreover, the prospective follow-up of large cohorts has provided and will offer critical material to identify strong prognostic factors. Whereas the outcomes of vascular manifestations of the disease has been recently improved due to targeted therapy, recent data have highlighted that mortality has not changed over the past 40 years. This reflects the absence of efficacy of current available drugs to counteract the fibrotic process. Nevertheless, several targeted immunity therapies, commonly with proven efficacy in other immune diseases, are about to be investigated in systemic sclerosis. Indeed, promising results in small and open studies have been reported. This article deals with recent insights into classification criteria, pathogenesis, organ involvements, outcome and current and possible future therapeutic options in systemic sclerosis.

Radiological thymus alterations in systemic sclerosis: our experience and a review of the literature

OBJECTIVE

Thymus alterations have been related to several autoimmune disorders. In particular, previous studies identified a significant frequency of gland abnormalities by chest high-resolution CT (HRCT) in SSc patients. In this study we aimed to investigate the prevalence of radiological thymic alterations and their correlation with clinical and serological features in a large SSc series.

METHODS

We retrospectively evaluated thymic shape on CT scans of 200 consecutive, unselected SSc patients aged over 30 years The presence of radiological abnormalities, i.e. enlarged gland >13 mm or nodular lesions >7 mm, was correlated with SSc clinico-serological features. Moreover, the patients were also classified using a second thickness cut-off of 7 mm in order to identify incomplete thymic involution.

RESULTS

Twenty-four of 200 (12%) SSc patients presented an abnormal thymus at HRCT, including hyperplasic (19/24) and nodular (5/24) glands. Otherwise, using the cut-off of 7 mm for gland thickness and excluding subjects with nodular thymus, 50/195 (25.6%) patients presented an incomplete thymic involution. Thymic radiological alterations are significantly correlated with younger age and diffuse cutaneous SSc. Moreover, an abnormally enlarged thymus tended to be more common in patients with shorter disease duration.

CONCLUSION

The present report on a large series of SSc patients further reinforces previous data present in the literature that includes other cohort studies and a number of anecdotal observations. Even though the actual role of thymus radiological abnormalities remains unclear, possible involvement of the gland in the early phase of immune-mediated SSc pathogenesis might be supposed.