Immunoregulatory defects of V alpha 24V+ beta 11+ NKT cells in development of Wegener's granulomatosis and relapsing polychondritis

Autoimmunity and Autoinflammation: Relapsing Polychondritis and VEXAS Syndrome Challenge

Relapsing polychondritis is a chronic autoimmune inflammatory condition characterized by recurrent episodes of inflammation at the level of cartilaginous structures and tissues rich in proteoglycans. The pathogenesis of the disease is complex and still incompletely elucidated. The data support the important role of a particular genetic predisposition, with HLA-DR4 being considered an allele that confers a major risk of disease occurrence. Environmental factors, mechanical, chemical or infectious, act as triggers in the development of clinical manifestations, causing the degradation of proteins and the release of cryptic cartilage antigens. Both humoral and cellular immunity play essential roles in the occurrence and perpetuation of autoimmunity and inflammation. Autoantibodies anti-type II, IX and XI collagens, anti-matrilin-1 and anti-COMPs (cartilage oligomeric matrix proteins) have been highlighted in increased titers, being correlated with disease activity and considered prognostic factors. Innate immunity cells, neutrophils, monocytes, macrophages, natural killer lymphocytes and eosinophils have been found in the perichondrium and cartilage, together with activated antigen-presenting cells, C3 deposits and immunoglobulins. Also, T cells play a decisive role in the pathogenesis of the disease, with relapsing polychondritis being considered a TH1-mediated condition. Thus, increased secretions of interferon γ, interleukin (IL)-12 and IL-2 have been highlighted. The "inflammatory storm" formed by a complex network of pro-inflammatory cytokines and chemokines actively modulates the recruitment and infiltration of various cells, with cartilage being a source of antigens. Along with RP, VEXAS syndrome, another systemic autoimmune disease with genetic determinism, has an etiopathogenesis that is still incompletely known, and it involves the activation of the innate immune system through different pathways and the appearance of the cytokine storm. The clinical manifestations of VEXAS syndrome include an inflammatory phenotype often similar to that of RP, which raises diagnostic problems. The management of RP and VEXAS syndrome includes common immunosuppressive therapies whose main goal is to control systemic inflammatory manifestations. The objective of this paper is to detail the main etiopathogenetic mechanisms of a rare disease, summarizing the latest data and presenting the distinct features of these mechanisms.

Development and validation of diagnostic and activity-assessing models for relapsing polychondritis based on laboratory parameters

Background

Relapsing polychondritis (RP) as a rare autoimmune disease is characterized by recurrent inflammation of the organs containing cartilage. Currently, no biomarkers have been integrated into clinical practice. This study aimed to construct and evaluate models based on laboratory parameters to aid in RP diagnosis, assess activity assessment, and explore associations with the pathological process.

Methods

RP patients and healthy controls (HCs) were recruited at the Peking Union Medical College Hospital from July 2017 to July 2023. Clinical data including Relapsing Polychondritis Disease Activity Index (RPDAI) score and laboratory tests were collected. Differences in laboratory data between RP patients and HCs and active and inactive patients were analyzed.

Results

The discovery cohort (cohort 1) consisted of 78 RP patients and 94 HCs. A model based on monocyte counts and neutrophil to lymphocyte ratio (NLR) could effectively distinguish RP patients from HCs with an AUC of 0.845. Active RP patients exhibited increased erythrocyte sedimentation rate, complement 3, platelet to lymphocyte ratio (PLR), NLR, and C-reactive protein to albumin ratio (CAR) compared with stable patients, which were also positively correlated with RPDAI. Notably, CAR emerged as an independent risk factor of disease activity (OR = 4.422) and could identify active patients with an AUC of 0.758. To confirm the reliability and stability of the aforementioned models, a replication cohort (cohort 2) was enrolled, including 79 RP patients and 94 HCs. The monocyte-combined NLR and CAR showed a sensitivity of 0.886 and 0.577 and a specificity of 0.830 and 0.833 in RP diagnosis and activity prediction, respectively. Furthermore, lower natural killer cell levels in RP patients and higher B-cell levels in active patients may contribute to elucidating the pathological mechanisms of disease occurrence and exacerbation.

Conclusions

The utilization of laboratory parameters provides cost-effective and valuable markers that can assist in RP diagnosis, identify disease activity, and elucidate pathogenic mechanisms.

Progress and challenges in the use of blood biomarkers in relapsing polychondritis

Relapsing polychondritis (RP) is a rare inflammatory disease with significant individual heterogeneity that involves systemic organs. The diagnosis of RP mainly depends on the clinical manifestations; currently, there are no molecular biomarkers routinely evaluated in clinical practice. Biomarkers have diagnostic or monitoring values and can predict response to treatment or the disease course. Over the years, many biomarkers have been proposed to facilitate diagnosis and prognosis. Unfortunately, ideal biomarkers to diagnose RP have not yet been discovered. Most of the molecular biomarkers in RP are immunological biomarkers, with autoantibodies and proteins related to cartilage damage in the blood being the most common. Alterations in some genes (HLA typing and UBA1 somatic mutation) were detected in patients with RP, which could serve as a potential biomarker for the diagnosis of RP. Moreover, proinflammatory cytokines and lymphocyte levels, and certain laboratory tests, have certain values of RP diagnosis and disease activity assessment but lack specificity and sensitivity. This review describes the different types of biomarkers and their clinical correlation with respect to the diagnosis of RP and disease activity. Research on biomarkers and disease pathology is ongoing to identify the ideal biomarkers that are sensitive and specific for RP.

Longitudinal monitoring of circulating immune cell phenotypes in anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is a necrotizing multiorgan autoimmune disease that affects small- to medium-sized blood vessels. Despite the improvements in treatments, half of the patients with AAV still experience disease relapses. In this review, we focus on peripheral leukocyte properties and phenotypes in patients with AAV. In particular, we explore longitudinal changes in circulating immune cell phenotypes during the active phase of the disease and treatment. The numbers and phenotypes of leukocytes in peripheral blood were differs between AAV and healthy controls, AAV in active versus inactive phase, AAV in treatment responders versus non-responders, and AAV with and without severe infection. Therefore, biomarkers detected in peripheral blood immune cells may be useful for longitudinal monitoring of disease activity in AAV.

Respiratory subtype of relapsing polychondritis frequently presents as difficult asthma: a descriptive study of respiratory involvement in relapsing polychondritis with 13 patients from a single UK centre

Introduction

Relapsing polychondritis is a rare multisystem vasculitis characterised by recurrent cartilage inflammation. Respiratory involvement, of which tracheobronchomalacia (TBM) is the commonest form, is difficult to treat and is linked to increased mortality. We describe 13 patients with respiratory involvement.

Methods

This is a retrospective study of all the patients with relapsing polychondritis at University Hospitals Coventry and Warwickshire NHS Trust (UHCW), a secondary care provider for ∼500 000. Only patients with respiratory involvement were included in this study.

Results

We identified 13 patients who fulfilled the inclusion criteria. Most patients were identified from the “difficult asthma” clinic. TBM was seen in 11 patients, whilst two patients had pleural effusions which resolved with immunosuppression and one patient had small airways disease. Computed tomography scans (inspiratory and expiratory) and bronchoscopy findings were useful in diagnosing TBM. Pulmonary function testing revealed significant expiratory flow abnormalities. All patients were treated with corticosteroids/disease-modifying anti-rheumatic drugs (DMARDs) and some were given cyclophosphamide or biological agents, although the response to cyclophosphamide (1 out of 4) or biologicals (2 out of 4) was modest in this cohort. Ambulatory continuous positive airway pressure ventilation was successful in four patients.

Conclusions

Relapsing polychondritis may be overlooked in “difficult asthma” clinics with patients having TBM (not asthma) and other features of relapsing polychondritis. Awareness of this condition is crucial to enable early diagnosis and interventions to reduce the risk of life-threatening airway collapse. A number of patients respond well to DMARDs and are able to minimise corticosteroid use.

Tracheobronchomalacia can present as “difficult asthma” and can be associated with relapsing polychondritis. Optimal management of relapsing polychondritis is through medical treatments and support for the damaged airway through positive airway pressure.https://bit.ly/2JGoq23

Propionate-producing bacteria in the intestine may associate with skewed responses of IL10-producing regulatory T cells in patients with relapsing polychondritis

Relapsing polychondritis (RP) is an inflammatory disease of unknown causes, characterized by recurrent inflammation in cartilaginous tissues of the whole body. Recently, researchers have reported that, in mouse experiments, altered gut microbe-dependent T cell differentiation occurred in gut associated lymphoid tissues. Here, we investigated whether gut microbe alteration existed, and if so, the alteration affected peripheral T cell differentiation in patients with RP. In an analysis of gut microbiota, we found increased annotated species numbers in RP patients compared with normal individuals. In the RP gut microbiota, we observed several predominant species, namely Veillonella parvula, Bacteroides eggerthii, Bacteroides fragilis, Ruminococcus bromii, and Eubacterium dolichum, all species of which were reported to associate with propionate production in human intestine. Propionate is a short-chain fatty acid and is suggested to associate with interleukin (IL)10-producing regulatory T (Treg) cell differentiation in gut associated lymphoid tissues. IL10 gene expressions were moderately higher in freshly isolated peripheral blood mononuclear cells (PBMC) of RP patients than those of normal individuals. Six hours after the initiation of the cell culture, regardless of the presence and absence of mitogen stimulation, IL10 gene expressions were significantly lower in RP patients than those in normal individuals. It is well known that PBMC of patients with autoimmune and inflammatory diseases show hyporesponsiveness to mitogen stimulation. We suggest that, in RP patients, continuous stimulation of intestinal T cells by excessive propionate leads to the spontaneous IL10 production and a subsequent refractory period of T cells in patients with RP. The hyporesponsiveness of Treg cells upon activation may associate with inflammatory cytokine production of PBMC and subsequently relate to chondritis in RP patients.

Corticosteroid Therapy for a Patient with Relapsing Polychondritis Complicated by IgG4-Related Disease

Relapsing polychondritis (RP) is a rare systemic disorder characterized by recurrent, widespread chondritis of the auricular, nasal, and tracheal cartilages. IgG4-related disease (IgG4-RD) is a systemic immune-mediated disease characterized by the infiltration of IgG4-bearing plasma cells into systemic organs. Although 25% to 35% of patients with RP have a concurrent autoimmune disease, coexistence of RP and IgG4-RD is rare. We herein report a case of RP complicated by IgG4-RD. A 63-year-old man developed recurrent bilateral ear pain and swelling, recurrent blurred and decreased vision, and migratory multiple joint pain, sequentially within one year. Fourteen months after the first symptom, he experienced dry cough and dyspnea with exertion. A computed tomography (CT) scan detected interstitial pneumonia, swelling of bilateral submandibular glands, bilateral hilar and mediastinal lymphadenopathy, and several nodules in bilateral kidneys. His serum levels of IgG and IgG4 were elevated. The biopsy specimen of auricular cartilage showed infiltrations of inflammatory cells and fibrosis consistent with RP. The IgG4-positive cells were not observed in auricular cartilage. The patient met the diagnostic criteria of RP, including bilateral auricular chondritis, conjunctivitis, iritis and polyarthritis. The biopsy specimens of lung and kidney revealed the significant infiltrations of IgG4-positive plasma cells and fibrosis. We also diagnosed him as having IgG4-RD, affecting bilateral submandibular glands, hilar and mediastinal lymph nodes, lungs, and kidneys. Thus, RP preceded the onset of IgG4-RD. Corticosteroid therapy improved the symptoms and CT scan findings. In conclusion, RP and IgG4-RD do coexist; however, the pathogenesis of their coexistence is unknown.

A nationwide study of the epidemiology of relapsing polychondritis

OBJECTIVE

Relapsing polychondritis (RP) is a rare autoimmune inflammatory disease that attacks mainly cartilaginous structures or causes serious damage in proteoglycan-rich structures (the eyes, heart, blood vessels, inner ear). This study shows results regarding the epidemiology, progression, and associations of this highly variable disease by collecting all cases from a 124-million-person-year Central European nationwide cohort.

METHODS

We used the Hungarian Health Care Database to identify all persons with possible RP infection. We followed patients who had International Classification of Diseases 10th edition code M94.1 at least once in their inpatient or outpatient records between January 1, 2002 and December 31, 2013 in Hungary. We classified these patients into disease severity groups by their drug consumption patterns between January 1, 2010 and December 31, 2013. We analyzed the regional distribution of RP incidences as well. Overall maps of comorbidity are presented with network layouts.

RESULTS

We identified 256 patients with RP among cumulatively 11.5 million registered inhabitants. We classified these patients into four severity classes as "extremely mild" (n=144), "mild" (n=22), "moderate" (n=41), and "severe" (n=4). Two additional groups were defined for patients without available drug data as "suspected only" (n=23) and "confirmed but unknown treatment" (n=22). The age and sex distributions of patients were similar to worldwide statistics. Indeed, the overall survival was good (95% confidence interval for 5 years was 83.6%-92.9% and for 10 years was 75.0%-88.3% which corresponds to the overall survival of the general population in Hungary), and the associations with other autoimmune disorders were high (56%) in Hungary. Almost any disease can occur with RP; however, the symptoms of chromosomal abnormalities are only incidental. Spondylosis can be a sign of the activation of RP, while Sjögren syndrome is the most frequent autoimmune association. Regional distribution of incidences suggests arsenic drinking water and sunlight exposure as possible triggering factors.

CONCLUSION

The good survival rate of RP in Hungary is probably associated with the early diagnosis of the disease.

Relapsing polychondritis: clinical presentations, disease activity and outcomes

Background

Relapsing polychondritis is a rare disease characterised by inflammation of cartilaginous and proteoglycan rich structures. As there are only a few published single centre case series from all across the world, we describe our experience with 26 patients at a tertiary centre in north India.

Methods

A retrospective study with all patients meeting Damiani and Levine’s modification of McAdam’s diagnostic criteria. Clinical details, investigations, disease activity assessment [(Relapsing Polychondritis Disease Activity Index (RPDAI)], treatment and outcomes were recorded.

Results

Ten men and sixteen women (median age 45 years) met the diagnostic criteria. Auricular chondritis (96%), arthritis (54%), hearing impairment (42%), ocular (42%), dermal (26%), cardiovascular (11%) and laryngotracheal involvement (11%) characterized the clinical presentations. The median RPDAI was 31 (range 9-66). Two patients died during observation. Overall survival was 92.3% (median survival 13.5 years).

Conclusions

Apart from reduced laryngotracheal involvement, RP in India was clinically similar to recorded patterns elsewhere.

Pathogenesis of relapsing polychondritis: a 2013 update

Relapsing polychondritis (RP) is a systemic inflammatory disease primarily affecting not only the cartilaginous structures of the ears, nose and tracheobronchial tree but also the joints, the inner ear, the eyes, and the cardiovascular system. RP is an immune-mediated disease during which target antigens are still unknown, but data from human studies and murine models strongly support a role of both Collagen Type II (CII) and matrilin-1 as potential candidates. RP is likely a Th1-mediated disease as serum levels of interferon (IFN)-γ, interleukin [IL]-12, and IL-2 parallel changes in disease activity, while the levels of Th2 cytokines do not. Serum levels of sTREM-1, interferon-γ, CCL4, vascular endothelial growth factor, and matrix metalloproteinases-3 are significantly higher in RP patients than in healthy donors, with sTREM-1 correlating with disease activity. Patients with active RP also have significantly higher levels of MCP-1, MIP-1β, MIF, and IL-8 than controls. These pro-inflammatory chemokines are involved in the modulation and recruitment of monocytes and neutrophils. Altogether, these data suggest that a complex cytokine network orchestrates the recruitment of infiltrating cells in RP lesions. Cytokine modulation using TNFα blockers, rituximab, anakinra, tocilizumab, and abatacept has recently been shown effective in some RP cases but further data are needed. Better understanding of the repertoire of infiltrating cells may provide interesting clues to further define the putative RP auto-antigens. Study of circulating mononuclear cells during RP flares may also provide crucial information about the ongoing cellular trafficking and recruitment processes involved in this rare disease.

Expansions of CD4+CD28– and CD8+CD28– T cells in Granulomatosis with Polyangiitis and Microscopic Polyangiitis Are Associated with Cytomegalovirus Infection But Not with Disease Activity

Objective.

T helper cells lacking CD28 (CD4+CD28–) have been implicated in the pathogenesis of granulomatosis with polyangiitis (Wegener; GPA) and microscopic polyangiitis (MPA). Expansions of CD4+CD28– and CD8+CD28– T cells have also been associated with latent cytomegalovirus (CMV) infection. We assessed these T cells with and without coexpression of CD56 and CD57 in relation to vasculitis as well as CMV status.

Methods.

Blood from 16 patients in remission (12 GPA, 4 MPA), 18 patients with active vasculitis (12 GPA, 6 MPA), and 20 healthy controls was examined by flow cytometry for expression of CD4, CD8, CD56, CD57, and CD28 on T cells. The influence of age, CMV status, presence of disease, and disease activity on T cell subpopulations was tested with multiple regression analyses.

Results.

In active vasculitis, the total numbers and proportion of lymphocytes were decreased. Total numbers of CD4+, CD8+, CD4+CD28–, CD8+CD28–, CD4+CD57+, and CD8+CD57+ T subpopulations were decreased to the same extent, implying unchanged proportions. Multivariate analyses showed no associations between vasculitis and CD28– or CD57+ T subpopulations, whereas immunoglobulin G antibodies to CMV were associated with expanded proportions of CD28– and CD57+ T cells, in both the CD4+ and the CD8+ compartments.

Conclusion.

CD28– and CD57+ T cells were associated with latent CMV infection and not with a diagnosis of GPA or MPA. Vasculitis assessment should include CMV status.

Patients with Wegener's granulomatosis demonstrate a relative deficiency and functional impairment of T-regulatory cells

An increased proportion of CD4(+) CD25(+) T cells has been reported in Wegener's granulomatosis (WG) and may represent an accumulation of regulatory T cells (Treg). CD25 is also expressed on recently activated effector T cells. We have determined the relative proportion of these subsets in a large patient cohort. The fraction of Treg in peripheral blood mononuclear cells from patients and healthy controls was determined by assessment of Foxp3 expression on CD4(+) CD25(+) T cells. The functional activity of Treg was determined by their ability to suppress proliferation and cytokine production in response to proteinase-3. Although WG patients demonstrated an increased fraction of CD4(+) CD25(+) T cells, the percentage of Foxp3-positive cells was decreased. In addition, the percentage of Treg was inversely related to the rate of disease relapse. CD4(+) CD25(hi) T cells were able to suppress T-cell proliferation to proteinase-3 in healthy controls and anti-neutrophil cytoplasm antibody (ANCA)- negative patients (at time of sampling) but not in ANCA-positive patients. In patients with active disease, an increased proportion of CD4(+) Foxp3(+) cells was associated with a more rapid disease remission. Patients with WG demonstrate abnormalities in the number and function of Treg and this is most pronounced in those with most active disease. This information is of value in understanding the pathogenesis and potential treatment of this disease.

Expansion of CD4+CD28- T cells producing high levels of interferon-{gamma} in peripheral blood of patients with multiple sclerosis

CD4(+) T cells that lack surface expression of the CD28 co-stimulatory molecule (CD4(+)CD28(-) T cells) were expanded in peripheral blood of patients with multiple sclerosis (MS) [5.20 +/- 1.67% vs 13.00 +/- 2.68% (healthy controls (HC) versus patients with MS)]. Both the CD4(+)CD28(+) and CD4(+)CD28(-) T-cell populations of patients with MS produced higher levels of interferon (IFN)-gamma compared with those in HC. In particular, the proportion of IFN-gamma(+) cells among CD4(+)CD28(-) T cells from patients with MS was considerably high. However, expression of co-stimulatory molecules including inducible costimulator (ICOS), activating natural killer receptors, or members of tumor necrosis factor receptor family that replace CD28 in CD4(+)CD28(-) T cells of patients with MS could not be identified. A unique subpopulation bearing the CD45RA(high)CCR7(-) phenotype was identified among the CD4(+)CD28(-) T cells of some patients with MS. Because only MS samples contained this CD45RA(high)CCR7(-) population attributed to terminally differentiated effector memory cells and lacked naive CD45RA(high)CCR7(+) cells, we suggest that CD4(+)CD28(-) T cells of patients with MS represent a cell population which is in more differentiated state than healthy subjects. In patients treated with IFN-beta-1b, IFN-gamma production from CD4(+)CD28(+) T cells was suppressed compared with that in untreated patients. On the contrary, in the CD4(+)CD28(-) population, production of IFN-gamma in IFN-beta-1b-treated patients was not significantly suppressed compared with that in untreated patients with MS. Thus, an additional treatment strategy that specifically targets this cell population may enhance the beneficial effect of IFN-beta on MS.

Effect of high fat diet on NKT cell function and NKT cell-mediated regulation of Th1 responses

Diet is one of the important factors that modulate immune responses. In the present study, we have examined the capacity of dietary lipids to modify immune responses in mice and we have investigated the contribution of glycolipid-reactive natural killer T (NKT) cells in this process. Mice fed, high fat diet (HFD; 21.2% fat, 0.20% cholesterol) for 3 weeks, as compared with mice fed standard fat diet (SFD; 4.3% fat, 0.03% cholesterol), showed significantly reduced interferon-gamma production in sera at 6 or 12 h after intraperitoneal injection of an NKT cell ligand, alpha-galactosylceramide. In contrast, production of interleukin-13 was significantly higher at 2 and 6 h in HFD fed mice compared with mice on SFD. No difference was detected in the serum interleukin-4 levels between these two groups of animals. The proportion of NKT cells in spleen and liver was reduced in mice fed HFD compared with those on SFD. In addition, activation of NKT cells assessed by up-regulation of CD69 was suppressed specifically in liver from mice fed HFD. Recall responses of conventional T cells and delayed-type hypersensitivity (Th1 type) against ovalbumin were significantly suppressed in mice fed HFD in comparison with those fed SFD. This suppression was not observed in CD1d-/- mice, suggesting that NKT cells in mice fed HFD played a role in suppressing Th1 responses. Taken together, our findings suggest a critical link between NKT cells, dietary lipid and adaptive immune responses.

Th1 or Th2 balance regulated by interaction between dendritic cells and NKT cells

If Th1 or Th2 polarization could be artificially manipulated, effective immune responses would be generated depending on nature of the targets. In this study we attempted to regulate CD40 expressions on dendritic cells (DCs) in order to modify the T cell response. It was found that reducing agents selectively inhibited surface expression of CD40 on DCs. This finding may provide a new strategy of DC-mediated modulation of the Th1/Th2 balance. It was also shown that NKT-produced Th1/Th2 cytokine balance was under control of negative feedback loop through DCs. Th1 cytokine-pretreated DCs mainly induced Th2 cytokine production, whereas Th2 cytokine-pretreated DCs induced Th1 cytokine production by alpha-galactosylceramide-stimulated NKT cells. The negative feedback regulation system could be applicable to therapeutics of various diseases based on immunological disorders.

Lower prevalence of circulating natural killer T cells in patients with angina: a potential novel marker for coronary artery disease

OBJECTIVE

Atherosclerosis is an inflammatory disease. Natural killer T cells are a unique lymphocyte subset that can recognize lipid antigens presented by CD1d and secrete copious amounts of pro-atherogenic cytokines such as interferon-gamma. We have previously shown that natural killer T cells accelerate atherosclerosis in mice and macrophages incubated with oxidized low-density lipoproteins induce natural killer T cells to produce interferon-gamma. Thus, whether the prevalence of natural killer T cells in peripheral blood is altered in patients with angina pectoris and its correlation with coronary risk factors was determined.

METHOD

Cell profiling was performed using flow cytometry in patients with stable angina, unstable angina (Braunwald IIIB), and healthy controls. Natural killer T cells in peripheral blood were identified by the expression of natural killer T specific invariant T cell receptor alpha-chain (Valpha24) and T cell receptor beta-chain (Vbeta11).

RESULTS

Prevalence of natural killer T (Valpha24-Vbeta11 double positive) cells was significantly decreased in patients with unstable angina and stable angina compared with that in controls. No significant differences were observed in the prevalence between unstable and stable angina. Reduction of natural killer T cells was independently associated with the presence of angina.

CONCLUSIONS

Lower prevalence of circulating natural killer T cells is related to the presence of coronary artery disease. As T cell receptor down-regulation or apoptosis after natural killer T cell activation and subsequent interferon-gamma release may contribute to atherogenesis, natural killer T cells can become a novel therapeutic target for the prevention and treatment of atherosclerotic vascular diseases.

Is PR3-ANCA formation initiated in Wegener's granulomatosis lesions? Granulomas as potential lymphoid tissue maintaining autoantibody production

In Wegener's granulomatosis (WG), antiproteinase 3 (PR3) autoantibodies (PR3-ANCA) are crucial in the development of generalized vasculitis. Wegener's pathognomonic lesion, a granulomatous inflammation of the upper and lower respiratory tract, contains abundant lymphocytes and macrophages. Lymphocyte clusters in germinal center-like formation within the granulomatous lesion are frequently observed, which suggests antigen-driven B cell maturation. Wegener's autoantigen PR3, the target for autoreactive B and T cells, is expressed in granulomatous lesions. Disease progression in WG is accompanied by a profound generalized alteration of T cell differentiation with an increase of effector memory T cells (CD4(+)CD28(-)). The cytokine profile suggests an aberrant Th1-type response either to an environmental trigger and/or the autoantigen PR3 itself. Staphylococcus aureus, a risk factor for disease exacerbation, is widely present in the upper airways in WG. The Ig gene repertoire from WG lesions indicates a predominance of VH3+ B cells with affinity to PR3 as well as to the S. aureus B cell superantigen SPA. Hence, within the WG lesion, S. aureus might support the maturation of PR3-affinity B cells that enter a germinal center reaction in contact with PR3 and T cells and expand, leading to PR3-ANCA production. Thus, granulomatous lesions could represent a potential lymphoid tissue-maintaining autoantibody production rather than a simple, random leukocyte accumulation in WG.

Immunoregulation of Autoimmunity by Natural Killer T Cells

Natural killer T (NKT) cells are a conserved subpopulation of lymphocytes that recognize glycolipid antigens in a CD1d context. Upon activation through their semi-invariant T cell receptor, these cells rapidly release large amounts of immunomodulating Th1 and Th2 cytokines. NKT cells have therefore been implicated in immune responses controlling various diseases, including infection, cancer, transplantation, and autoimmunity. Stimulation of the immunoregulatory capacity of NKT cells by the prototypical antigen alpha-galactosylceramide results in amelioration of disease in several animal models. This review will focus on the current knowledge of human NKT cells and their role in autoimmune diseases. The features of these cells and their importance in regulation of autoimmunity suggest that NKT cell-based therapies might be an interesting approach for the treatment of autoimmune diseases.

Off balance: T-cells in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides

There is substantial evidence that T-cells are off balance in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides. Genetic risk factors may influence shaping of the TCR repertoire and regulatory control of T-cells in predisposed individuals. T-cells are found in inflammatory lesions. Vigorous Th1-type responses are seen in Wegener's granulomatosis and microscopic angiitis, whereas a Th2-type response predominates in Churg-Strauss syndrome. Oligoclonality and shortened telomers indicate antigen-driven clonal expansion and replicative senescence of T-cells in ANCA-associated vasculitides. Potent CD28(-) Th1-type cells displaying an effector-memory/late differentiated, senescent phenotype are expanded in peripheral blood and are found in granulomatous lesions in Wegener's granulomatosis. Differences in proliferative peripheral blood T-cell responses to the autoantigens proteinase 3 (PR3)- and myeloperoxidase (MPO) have not consistently been detected between patients with ANCA-associated vasculitides and healthy controls in vitro. To recognize an autoantigen, break tolerance, and maintain autoimmune disease T- and B-cells require particular triggers and lymphoid structures. There is preliminary evidence of lymphoid-like structures and possible maturation of autoreactive PR3-ANCA-specific B-cells in granulomatous lesions in Wegener's granulomatosis. Alteration of the T-cell response and anomalous autoantigen-presentation in lymphoid-structures could facilitate development of autoimmune disease in ANCA-associated vasculitides.