CD28 negative T cells are enriched in granulomatous lesions of the respiratory tract in Wegener's granulomatosis

Aging in Granulomatosis with Polyangiitis and Microscopic Polyangiitis: From Pathophysiology to Clinical Management

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) predominantly affect individuals aged 55-75 years, with granulomatosis with polyangiitis (GPA) being diagnosed most often between 55 and 65 years and microscopic polyangiitis (MPA) between 65 and 75 years. Owing to the general increase in life expectancy, the average age at diagnosis increases, encompassing also those over 75 years old. Unfortunately, the exclusion of these older patients from many clinical trials has limited our understanding of the progression of these diseases in older subjects. The role of immunosenescence and aging in AAV pathogenesis and progression is underexplored, despite potential implications in the understanding of the disease, and potentially for disease management. Although AAV manifestations are largely consistent across age groups, certain features, such as renal involvement and the association with interstitial lung disease, may be more prevalent in older patients. Frailty must be a key consideration in therapeutic decision-making, especially when balancing the efficacy of immunosuppressants with potential side effects. Recent evidence supports the use of rituximab in addition to low-dose glucocorticoids for remission induction in life- or organ-threatening AAV, including in older populations. Furthermore, preliminary evidence supports that avacopan might be as efficient as glucocorticoids in these patients. The immunosuppressive treatment of AAV reduces the immune response to environmental pathogens, with rituximab worsening age-related hypogammaglobulinemia. Thus, prophylactic measures, including vaccination and Pneumocystis pneumonia prevention, as well as strategies to mitigate glucocorticoid side effects, should be implemented in AAV management.

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.

[Pathogenesis of ANCA-associated vasculitides in 2021: An update]

Anticytoplasmic neutrophil antibodies (ANCA)-associated vasculitis (AAV) are rare systemic immune-mediated diseases characterized by small vessel necrotizing vasculitis and/or respiratory tract inflammation. Over the last 2 decades, anti-MPO vasculitis mouse model has enlightened the role of ANCA, neutrophils, complement activation, T helper cells (Th1, Th17) and microbial agents. In humans, CD4T cells have been extensively studied, while the dramatic efficacy of rituximab demonstrated the key role of B cells. Many areas of uncertainty remain, such as the driving force of GPA extra-vascular granulomatous inflammation and the relapse risk of anti-PR3 AAV pathogenesis. Animal models eventually led to identify complement activation as a promising therapeutic target. New investigation tools, which permit in depth immune profiling of human blood and tissues, may open a new era for the studying of AAV pathogenesis.

Immune Cells Profiling in ANCA-Associated Vasculitis Patients-Relation to Disease Activity

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are a group of necrotizing multiorgan autoimmune vasculitides that predominantly affect small blood vessels and are associated with the presence of ANCAs. The aim was to assess regulatory and effector cell populations accompanied by the suPAR biomarker level and link the so-defined immune state to the AAV disease activity. The research involved a multicomponent description of an immune state encompassing a range of B and T cell subsets such as transitional/regulatory B cells (CD19+CD24++CD38++), naïve B cells (CD19+CD24INTCD38INT), Th17 cells, T regulatory cells (CD4+CD25+FoxP3+) and cytotoxic CD4+CD28- cells by flow cytometry. The suPAR plasma level was measured by ELISA. The results indicate that AAV is associated with an increased suPAR plasma level and immune fingerprint characterized by an expansion of Th17 cells and T cells lacking the costimulatory molecule CD28, accompanied by a decrease of regulatory populations (Tregs and transitional B cells) and NK cells. Decreased numbers of regulatory T cells and transitional B cells were shown to be linked to activation of the AAV disease while the increased suPAR plasma level-to AAV-related deterioration of kidney function. The observed immune fingerprint might be a reflection of peripheral tolerance failure responsible for development and progression of ANCA-associated vasculitides.

Granulomatous Inflammation in ANCA-Associated Vasculitis

ANCA-associated vasculitis (AAV) comprises granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). While systemic vasculitis is a hallmark of all AAV, GPA is characterized by extravascular granulomatous inflammation, preferentially affecting the respiratory tract. The mechanisms underlying the emergence of neutrophilic microabscesses; the appearance of multinucleated giant cells; and subsequent granuloma formation, finally leading to scarred or destroyed tissue in GPA, are still incompletely understood. This review summarizes findings describing the presence and function of molecules and cells contributing to granulomatous inflammation in the respiratory tract and to renal inflammation observed in GPA. In addition, factors affecting or promoting the development of granulomatous inflammation such as microbial infections, the nasal microbiome, and the release of damage-associated molecular patterns (DAMP) are discussed. Further, on the basis of numerous results, we argue that, in situ, various ways of exposure linked with a high number of infiltrating proteinase 3 (PR3)- and myeloperoxidase (MPO)-expressing leukocytes lower the threshold for the presentation of an altered PR3 and possibly also of MPO, provoking the local development of ANCA autoimmune responses, aided by the formation of ectopic lymphoid structures. Although extravascular granulomatous inflammation is unique to GPA, similar molecular and cellular patterns can be found in both the respiratory tract and kidney tissue of GPA and MPA patients; for example, the antimicrobial peptide LL37, CD163⁺ macrophages, or regulatory T cells. Therefore, we postulate that granulomatous inflammation in GPA or PR3-AAV is intertwined with autoimmune and destructive mechanisms also seen at other sites.

CD8+ T Cells in GCA and GPA: Bystanders or Active Contributors?

Vasculitis refers to inflammation of blood vessels and can cause a variety of serious complications depending on which vessels are affected. Two different forms of vasculitis are Giant Cell Arteritis (GCA) and Granulomatosis with Polyangiitis (GPA). GCA is the most common form of vasculitis in adults affecting the large arteries and can lead to visual impairment and development of aneurysms. GPA affects small- and medium-sized blood vessels predominantly in the lungs and kidneys resulting in organ failure. Both diseases can potentially be fatal. Although the pathogenesis of GCA and GPA are incompletely understood, a prominent role for CD4+ T cells has been implicated in both diseases. More recently, the role of CD8+ T cells has gained renewed interest. CD8+ T cells are important players in the adaptive immune response against intracellular microorganisms. After a general introduction on the different forms of vasculitis and their association with infections and CD8+ T cells, we review the current knowledge on CD8+ T-cell involvement in the immunopathogenesis of GCA and GPA focusing on phenotypic and functional features of circulating and lesional CD8+ T cells. Furthermore, we discuss to which extent aging is associated with CD8+ T-cell phenotype and function in GCA and GPA.

Urinary and serum soluble CD25 complements urinary soluble CD163 to detect active renal anti-neutrophil cytoplasmic autoantibody-associated vasculitis: a cohort study

Background

Early detection of renal involvement in anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is of major clinical importance to allow prompt initiation of treatment and limit renal damage. Urinary soluble cluster of differentiation 163 (usCD163) has recently been identified as a potential biomarker for active renal vasculitis. However, a significant number of patients with active renal vasculitis test negative using usCD163. We therefore studied whether soluble CD25 (sCD25), a T cell activation marker, could improve the detection of renal flares in AAV.

Methods

sCD25 and sCD163 levels in serum and urine were measured by enzyme-linked immunosorbent assay in 72 patients with active renal AAV, 20 with active extrarenal disease, 62 patients in remission and 18 healthy controls. Urinary and blood CD4+ T and CD4+ T effector memory (TEM) cell counts were measured in 22 patients with active renal vasculitis. Receiver operating characteristics (ROC) curves were generated and recursive partitioning was used to calculate whether usCD25 and serum soluble CD25 (ssCD25) add utility to usCD163.

Results

usCD25, ssCD25 and usCD163 levels were significantly higher during active renal disease and significantly decreased after induction of remission. A combination of usCD25, usCD163 and ssCD25 outperformed all individual markers (sensitivity 84.7%, specificity 95.1%). Patients positive for sCD25 but negative for usCD163 (n = 10) had significantly higher C-reactive protein levels and significantly lower serum creatinine and proteinuria levels compared with the usCD163-positive patients. usCD25 correlated positively with urinary CD4+ T and CD4+ TEM cell numbers, whereas ssCD25 correlated negatively with circulating CD4+ T and CD4+ TEM cells.

Conclusion

Measurement of usCD25 and ssCD25 complements usCD163 in the detection of active renal vasculitis.

Unraveling the identity of FoxP3+ regulatory T cells in Granulomatosis with Polyangiitis patients

Human CD4+FoxP3+T-cells are heterogeneous in function and include not only suppressive cells (Tregs), but also effector cells that transiently express FoxP3 upon activation. Previous studies in Granulomatosis with Polyangiitis (GPA-)patients have demonstrated an increase in FoxP3+T-cells with impaired suppressive capacity and an increase in Th17 cells. We hypothesized that the increase in FoxP3+T-cells results from an increase in non-suppressive effector-like cells. The frequency of circulating CD4+FoxP3+T-cell subsets were determined by flow cytometry in 46 GPA-patients in remission and 22 matched healthy controls (HCs). Expression levels of FoxP3 and CD45RO were used to distinguish between CD45RO- FoxP3low resting Tregs (rTreg), CD45RO+FoxP3high activated Tregs (aTreg) and CD45RO+FoxP3low proinflammatory non-suppressive T-cells (nonTreg). Intracellular expression of IFNγ, IL-17, and IL-21 was compared within these subsets. We found a significant increase in the frequency of nonTreg cells in GPA-patients as compared with HCs. Importantly, within the nonTreg subset, antineutrophil cytoplasmic autoantibody (ANCA-)positive patients demonstrated a significantly higher percentage of IL-17+ and IL-21+ cells when compared with ANCA-negative patients and HCs. Moreover, expanded nonTregs from ANCA-positive patients induced excessive proliferation of responder cells in vitro and exhibited higher IL-21 production. Production of IL-17 and IL-21 in non-suppressive FoxP3+T-cells may point toward a pathogenic role in ANCA formation.

Th17 cells in renal inflammation and autoimmunity

Th17 cells are a distinct lineage of T-cells. These T-cells express IL-17A and the lineage-defining transcription factor RORγt. Th17 cells have a pivotal, physiological role in host defense against pathogens. These pro-inflammatory T-cells are also key players in autoimmunity and a pathogenic role has been demonstrated in several diseases such as rheumatoid arthritis or psoriasis. Recently, there is evidence that Th17 cells may drive renal inflammation and renal autoimmunity in anti-neutrophil-cytoplasmic-antibody-(ANCA)-vasculitis and systemic lupus erythematosus. The aim of this review is to discuss the possible involvement of Th17 cells in renal autoimmunity and its value for future therapeutic approaches.

The NKG2D/NKG2DL Axis in the Crosstalk Between Lymphoid and Myeloid Cells in Health and Disease

Natural killer group 2, member D (NKG2D) receptor is a type II transmembrane protein expressed by both innate and adaptive immune cells, including natural killer (NK) cells, CD8+ T cells, invariant NKT cells, γδ T cells, and some CD4+ T cells under certain pathological conditions. NKG2D is an activating NK receptor that induces cytotoxicity and production of cytokines by effector cells and supports their proliferation and survival upon engagement with its ligands. In both innate and T cell populations, NKG2D can costimulate responses induced by other receptors, such as TCR in T cells or NKp46 in NK cells. NKG2D ligands (NKG2DLs) are remarkably diverse. Initially, NKG2DL expression was typically attributed to stressed, infected, or transformed cells, thus signaling “dysregulated-self.” However, many reports indicated their expression under homeostatic conditions, usually in the context of cell activation and/or proliferation. Myeloid cells, including macrophages and dendritic cells (DCs), are among the first cells sensing and responding to pathogens and tissue damage. By secreting a plethora of soluble mediators, by presenting antigens to T cells and by expressing costimulatory molecules, myeloid cells play vital roles in inducing and supporting responses of other immune cells in lymphoid organs and tissues. When activated, both macrophages and DCs upregulate NKG2DLs, thereby enabling them with additional mechanisms for regulating lymphocyte responses. In this review, we will focus on the expression of NKG2D by innate and adaptive lymphocytes, the regulation of NKG2DL expression on myeloid cells, and the contribution of the NKG2D/NKG2DL axis to the crosstalk of myeloid cells with NKG2D-expressing lymphocytes. In addition, we will highlight pathophysiological conditions associated with NKG2D/NKG2DL dysregulation and discuss the putative involvement of the NKG2D/NKG2DL axis in the lymphocyte/myeloid cell crosstalk in these diseases.

Pathogenetic and Clinical Aspects of Anti-Neutrophil Cytoplasmic Autoantibody-Associated Vasculitides

Anti-neutrophil cytoplasmic autoantibodies (ANCA) targeting proteinase 3 (PR3) and myeloperoxidase expressed by innate immune cells (neutrophils and monocytes) are salient diagnostic and pathogenic features of small vessel vasculitis, comprising granulomatosis with polyangiitis (GPA), microscopic polyangiitis, and eosinophilic GPA. Genetic studies suggest that ANCA-associated vasculitides (AAV) constitute separate diseases, which share common immunological and pathological features, but are otherwise heterogeneous. The successful therapeutic use of anti-CD20 antibodies emphasizes the prominent role of ANCA and possibly other autoantibodies in the pathogenesis of AAV. However, to elucidate causal effects in AAV, a better understanding of the complex interplay leading to the emergence of B lymphocytes that produce pathogenic ANCA remains a challenge. Different scenarios seem possible; e.g., the break of tolerance induced by a shift from non-pathogenic toward pathogenic autoantigen epitopes in inflamed tissue. This review gives a brief overview on current knowledge about genetic and epigenetic factors, barrier dysfunction and chronic non-resolving inflammation, necro-inflammatory auto-amplification of cellular death and inflammation, altered autoantigen presentation, alternative complement pathway activation, alterations within peripheral and inflamed tissue-residing T- and B-cell populations, ectopic lymphoid tissue neoformation, the characterization of PR3-specific T-cells, properties of ANCA, links between autoimmune disease and infection-triggered pathology, and animal models in AAV.

T-cell immunology in sarcoidosis: Disruption of a delicate balance between helper and regulatory T-cells

PURPOSE OF REVIEW

Although the aetiology of sarcoidosis is not yet completely understood, immunological changes within the T-cell compartment are characteristic for an exaggerated antigen-driven immune response. In this review, we describe the most recent findings on T-cell subset responses and regulation in sarcoidosis. We discuss how future immunological research can advance the field to unravel pathobiological mechanisms of this intriguingly complex disease.

RECENT FINDINGS

Research into the field of T-cell plasticity has recently challenged the long-held T helper type 1 (Th1) paradigm in sarcoidosis and striking parallels with autoimmune disorders and common variable immunodeficiency were recognized. For instance, it was demonstrated that Th17.1-cells rather than Th1-cells are responsible for the exaggerated IFN-γ production in pulmonary sarcoidosis. Furthermore, impaired regulatory T-cell function and alterations within the expression of co-inhibitory receptors that control T-cell responses, such as PD-1, CTLA-4 and BTNL2, raise new questions regarding T-cell regulation in pulmonary sarcoidosis.

SUMMARY

It becomes increasingly clear that Th17(.1)-cells and regulatory T-cells are key players in sarcoidosis T-cell immunology. New findings on plasticity and co-inhibitory receptor expression by these subsets help build a more comprehensive model for T-cell regulation in sarcoidosis and will finally shed light on the potential of new treatment modalities.

The story of CD4+ CD28- T cells revisited: solved or still ongoing?

CD4⁺CD28⁻ T cells are a unique type of proinflammatory T cells characterised by blockade of costimulatory CD28 receptor expression at the transcriptional level, which is still reversible by IL-12. In healthy individuals older than 65 years, these cells may accumulate to up to 50% of total CD4⁺ T lymphocytes as in many immune-mediated diseases, immunodeficiency, and specific infectious diseases. Here we focus on CD4⁺CD28⁻ T cells in chronic immune-mediated diseases, summarizing various phenotypic and functional characteristics, which vary depending on the underlying disease, disease activity, and concurrent treatment. CD4⁺CD28⁻ T cells present as effector/memory cells with increased replicative history and oligoclonality but reduced apoptosis. As an alternative costimulatory signal instead of CD28, not only natural killer cell receptors and Toll-like receptors, but also CD47, CTLA-4, OX40, and 4-1BB have to be considered. The proinflammatory and cytotoxic capacities of these cells indicate an involvement in progression and maintenance of chronic immune-mediated disease. So far it has been shown that treatment with TNF-α blockers, abatacept, statins, and polyclonal antilymphocyte globulins (ATG) mediates reduction of the CD4⁺CD28⁻ T cell level. The clinical relevance of targeting CD4⁺CD28⁻ T cells as a therapeutic option has not been examined so far.

β2-Microglobulin deficiency causes a complex immunodeficiency of the innate and adaptive immune system

BACKGROUND

Most patients with MHC class I (MHC-I) deficiency carry genetic defects in transporter associated with antigen processing 1 (TAP1) or TAP2. The clinical presentation can vary, and about half of the patients have severe skin disease. Previously, one report described β2-microglobulin (β2m) deficiency as another monogenetic cause of MHC-I deficiency, but no further immunologic evaluation was performed.

OBJECTIVE

We sought to describe the molecular and immunologic features of β2m deficiency in 2 Turkish siblings with new diagnoses.

METHODS

Based on clinical and serologic findings, the genetic defect was detected by means of candidate gene analysis. The immunologic characterization comprises flow cytometry, ELISA, functional assays, and immunohistochemistry.

RESULTS

Here we provide the first extensive clinical and immunologic description of β2m deficiency in 2 siblings. The sister had recurrent respiratory tract infections and severe skin disease, whereas the brother was fairly asymptomatic but had bronchiectasis. Not only polymorphic MHC-I but also the related CD1a, CD1b, CD1c, and neonatal Fc receptor molecules were absent from the surfaces of β2m-deficient cells. Absent neonatal Fc receptor surface expression led to low serum IgG and albumin levels in both siblings, whereas the heterozygous parents had normal results for all tested parameters except β2m mRNA (B2M) expression. Similar to TAP deficiency in the absence of a regular CD8 T-cell compartment, CD8(+) γδ T cells were strongly expanded. Natural killer cells were normal in number but not "licensed to kill."

CONCLUSION

The clinical presentation of patients with β2m deficiency resembles that of patients with other forms of MHC-I deficiency, but because of the missing stabilizing effect of β2m on other members of the MHC-I family, the immunologic defect is more extensive than in patients with TAP deficiency.

Increased frequency of circulating IL-21 producing Th-cells in patients with granulomatosis with polyangiitis (GPA)

INTRODUCTION

The present study aimed to explore a possible role for IL-21 producing Th-cells in the immunopathogenesis of granulomatosis with polyangiitis (GPA).

METHODS

Peripheral blood from 42 GPA patients in remission and 29 age-matched healthy controls (HCs) were stimulated in vitro, and the frequencies of IL-21 producing Th-cells were determined by flow cytometry. Since Th17-cells produce a low level of IL-21, IL-17 was also included in the analysis. Given that IL-21 is a hallmark cytokine for T follicular helper cells (T(FH)), we next evaluated the expression of their key transcription factor BCL-6 by RT-PCR and flow cytometry. To investigate the effect of IL-21 on autoantibody-production, PBMCs from GPA patients were stimulated in vitro with BAFF/IL-21 and total IgG and ANCA levels were measured in supernatants. In addition, the expression of IL-21-receptor on B-cells was analyzed.

RESULTS

Percentages of IL-21 producing Th-cells were significantly elevated in GPA-patients compared to HCs, and were restricted to ANCA-positive patients. The expression of BCL-6 was significantly higher in ANCA-positive GPA-patients, as compared with ANCA-negative patients and HCs. IL-21 enhanced the production of IgG and ANCA in vitro in stimulated PBMCs from GPA patients. No difference was found in the expression of the IL-21-receptor on B-cells between ANCA-negative patients, ANCA-positive patients, and HCs.

CONCLUSION

The increased frequency of circulating IL-21 producing Th-cells in ANCA-positive GPA patients and the stimulating capacity of IL-21 on ANCA-production suggest a role for these cells in the immunopathogenesis of GPA. Blockade of IL-21 could constitute a new therapeutic strategy for GPA.

T cells in vascular inflammatory diseases

Inflammation of the human vasculature is a manifestation of many different diseases ranging from systemic autoimmune diseases to chronic inflammatory diseases, in which multiple types of immune cells are involved. For both autoimmune diseases and chronic inflammatory diseases several observations support a key role for T lymphocytes in these disease pathologies, but the underlying mechanisms are poorly understood. Previous studies in several autoimmune diseases have demonstrated a significant role for a specific subset of CD4⁺ T cells termed effector memory T (T_EM) cells. This expanded population of T_EM cells may contribute to tissue injury and disease progression. These cells exert multiple pro-inflammatory functions through the release of effector cytokines. Many of these cytokines have been detected in the inflammatory lesions and participate in the vasculitic reaction, contributing to recruitment of macrophages, neutrophils, dendritic cells, natural killer cells, B cells, and T cells. In addition, functional impairment of regulatory T cells paralyzes anti-inflammatory effects in vasculitic disorders. Interestingly, activation of T_EM cells is uniquely dependent on the voltage-gated potassium Kv1.3 channel providing an anchor for specific drug targeting. In this review, we focus on the CD4⁺ T cells in the context of vascular inflammation and describe the evidence supporting the role of different T cell subsets in vascular inflammation. Selective targeting of pathogenic T_EM cells might enable a more tailored therapeutic approach that avoids unwanted adverse side effects of generalized immunosuppression by modulating the effector functions of T cell responses to inhibit the development of vascular inflammation.

Signal tranducers and activators of transcription: expression and function in anti-neutrophil cytoplasmic antibody-associated vasculitis

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is an autoimmune small vessel vasculitis. Despite the role of autoantibodies, T cells play an essential role in pathogenesis and are abnormal in AAV. Signal transducers and activators of transcription (STAT) affect immunoregulation and T-cell homeostasis. Therefore, the present study examined the ex vivo basal expression of the activated forms of STAT5 [phosphorylated (p)STAT5] and STAT3 (pSTAT3) in AAV and analyzed the function of two signaling pathways linked to these transcription factors. In total, 31 patients with AAV and 16 age-matched healthy controls (HCs) were enrolled. CD3+ T cells from peripheral blood were analyzed directly ex vivo by a fluorescence-activated cell sorter for basal expression of pSTAT5 and pSTAT3. Expression was also analyzed in T cells following short-term stimulation with interleukin (IL)-2 or -10. The basal expression of pSTAT5/3 in T cells was similar to AAV patients and HC. Following stimulation with IL-2 or -10, expression of pSTAT5/3 increased in AAV subjects compared with HC. Basal expression of pSTAT3 correlated with the relapse rate in AAV. In conclusion, STAT3 and STAT5 mediated signaling pathways were functionally intact in AAV patients and exhibited hyper-responsiveness to IL-2 and -10 stimuli. Thus, T-cell abnormalities in AAV are not promoted by an altered basal expression of pSTAT5/3 or dysfunction of the IL-2/-10 signaling pathways, in which STAT5/3 are essential.

Abnormal expression pattern of the IL-2 receptor β-chain on CD4+ T cells in ANCA-associated vasculitis

BACKGROUND/AIM

ANCA-associated vasculitis (AAV) is a small-vessel vasculitis of autoimmune origin. In addition to autoantibodies, T cells have a pivotal pathophysiological role in this disease. T-cell homeostasis and immune tolerance critically depend on IL-2 and its receptor expressed by T cells. In this study, we investigated the IL-2 receptor (IL-2r) expression on CD4(+) T cells in AAV.

METHODS

Thirty patients with AAV and 15 age-matched healthy controls (HC) were enrolled. T cells from peripheral blood were analysed by flow cytometry for expression of the IL-2r α - and β-chain.

RESULTS

The IL-2r α-chain was overexpressed in AAV as compared to HC (36 ± 16% versus 20 ± 9%, P < 0.005). The IL-2r-β-chain expression was significantly reduced on CD25(+) CD4(+) T-cells and CD4(+)CD25(+)FoxP3(pos) regulatory T-cells (Tregs; AAV versus HC: 48 ± 14% versus 62 ± 9%, P = 0.002 and 38 ± 18% versus 68 ± 5%, P = 0.002). Low β -chain expression in AAV was associated with relapsing disease and systemic vasculitis with renal involvement.

CONCLUSION

The IL-2r expression pattern is abnormal in AAV. To our knowledge, we are the first to show that the β -chain expression is drastically diminished on T cells in AAV and related to a less favorable disease course. Given the indispensable function of the β -chain in IL-2 signaling of T cells, diminished expression may contribute to disturbed immune homeostasis in AAV.

NKG2D stimulated T-cell autoreactivity in giant cell arteritis and polymyalgia rheumatica

OBJECTIVE

To investigate functional expression of NKG2D on CD4 and CD8 T-cells in patients with giant cell arteritis (GCA) and polymyalgia rheumatica (PMR).

METHODS

Peripheral blood was drawn from patients with GCA (n=16), PMR (n=78) and healthy controls (HC, n=64). Tissue samples were obtained from GCA patients and controls. Proliferation and cytokine production assays were performed using CFSE and intracellular IFN-γ or TNF-α staining, respectively, and flow cytometry analysis. Immunofluorescence and immunohistology were applied to analyse the presence of NKG2D-expressing T-cells and NKG2D-ligands in temporal arteries, respectively. mRNA levels of NKG2D-ligands were determined by RT-PCR.

RESULTS

In both GCA and PMR patients, NKG2D was preferentially expressed on senescent CD4CD28(-) and CD8CD28(-), as well as on CD8CD28 T-cells. Frequencies of senescent T-cells were increased in GCA and PMR patients compared to HC. In GCA tissue samples, infiltrating T-cells were predominately CD28(-). NKG2D expressing T-cells concentrated around the vasa vasorum of the adventitia. Antigenic stimulation induced rapid up-regulation of NKG2D on CD4CD28(-) and CD4CD28 T-cells, whereas TNF-α and interleukin-15 enhanced NKG2D expression on senescent CD4 and CD8 T-cells only. NKG2D cross-linkage augmented anti-CD3 triggered proliferation, IFN-γ and TNF-α production of CD8 T-cells. In CD4CD28(-) T-cells, NKG2D ligation resulted in increased IFN-γ production only. NKG2D ligands were expressed in temporal arteries from GCA patients, particularly in the adventitial and medial layers of affected vessels.

CONCLUSIONS

NKG2D is functionally expressed on CD4CD28(-) and CD8 T-cells in GCA and PMR. NKG2D-ligands are present in temporal arteries and may co-stimulate NKG2D expressing T-cells.

Th17 expansion in granulomatosis with polyangiitis (Wegener's): the role of disease activity, immune regulation and therapy

INTRODUCTION

In autoimmune diseases, IL-17 producing T-cells (Th17), a pro-inflammatory subset of T-cells, are pathophysiologically involved. There is little knowledge on the role of Th17 cells in granulomatosis with polyangiitis (GPA). In the present study, we investigated Th17 cells, Tregs and subsets of circulating Th17 cells in GPA and related results to disease activity.

METHODS

42 GPA patients in remission, 18 with active disease and 14 healthy controls (HC) were enrolled. Th17 cells, their subsets and regulatory T-cells were determined by intracellular fluorescence activated cell sorter (FACS). Data are given as mean percentage ±SD of total T-helper-cells.

RESULTS

Th17 cells are expanded in active and quiescent GPA as compared to HC (1.7±1.4% vs. 0.7 ±0.3%, P = 0.006 and 1.9 ±1.5% vs. 0.7 ±0.3%, P<0.0001). Th17 expansion is stable over time and does not decline when remission is achieved. However, a negative association of Th17 cells and steroid dosage is observed (r=-0.46, P = 0.002). The Th17 expansion was not balanced by Tregs as indicated by skewed Th17/Treg ratios in active and quiescent GPA. Th17 subsets co-producing IFNγ or IL-10 are significantly increased in GPA. GPA patients in remission not receiving maintenance therapy have significantly more IL-10/IL-17A double positive T-cells than HC (0.0501 ±0.031% vs. 0.0282 ±0.016%, P = 0.007).

CONCLUSIONS

We provide evidence for a persistent, unbalanced expansion of Th17 cells and Th17 subsets which seems to be independent of disease activity. Maintenance therapy reduces -but does not normalize- Th17 expansion.

Apoptotic effects of antilymphocyte globulins on human pro-inflammatory CD4+CD28- T-cells

Background

Pro-inflammatory, cytotoxic CD4⁺CD28⁻ T-cells with known defects in apoptosis have been investigated as markers of premature immuno-senescence in various immune-mediated diseases. In this study we evaluated the influence of polyclonal antilymphocyte globulins (ATG-Fresenius, ATG-F) on CD4⁺CD28⁻ T-cells in vivo and in vitro.

Principal Findings

Surface and intracellular three colour fluorescence activated cell sorting analyses of peripheral blood mononuclear cells from 16 consecutive transplant recipients and short-term cell lines were performed. In vivo, peripheral levels of CD3⁺CD4⁺CD28⁻ T-cells decreased from 3.7±7.1% before to 0±0% six hours after ATG-F application (P = 0.043) in 5 ATG-F treated but not in 11 control patients (2.9±2.9% vs. 3.9±3.0%). In vitro, ATG-F induced apoptosis even in CD4⁺CD28⁻ T-cells, which was 4.3-times higher than in CD4⁺CD28⁺ T-cells. ATG-F evoked apoptosis was partially reversed by the broad-spectrum caspase inhibitor benzyloxycarbonyl (Cbz)-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD-fmk) and prednisolon-21-hydrogensuccinate. ATG-F triggered CD25 expression and production of pro-inflammatory cytokines, and induced down-regulation of the type 1 chemokine receptors CXCR-3, CCR-5, CX3CR-1 and the central memory adhesion molecule CD62L predominately in CD4⁺CD28⁻ T-cells.

Conclusion

In summary, in vivo depletion of peripheral CD3⁺CD4⁺CD28⁻ T-cells by ATG-F in transplant recipients was paralleled in vitro by ATG-F induced apoptosis. CD25 expression and chemokine receptor down-regulation in CD4⁺CD28⁻ T-cells only partly explain the underlying mechanism.

The Molecular Biology and Treatment of Systemic Vasculitis in Children

Primary systemic vasculitides are rare in childhood but are associated with significant morbidity and mortality. The cause of the majority of vasculitides is unknown, although it is likely that a complex interaction between environmental factors, such as infections and inherited host responses, triggers the disease and determines the vasculitis phenotype. Several genetic polymorphisms in vasculitides have now been described, which may be relevant in terms of disease predisposition or development of disease complications. Treatment regimens continue to improve with the use of different immunosuppressive medications and newer therapeutic approaches such as biologic agents. This chapter reviews recent studies shedding light on the pathogenesis of vasculitis with emphasis on molecular biology where known, and summarizes current treatment strategies. We discuss new emerging challenges particularly with respect to the long-term cardiovascular morbidity for children with systemic vasculitis and emphasize the importance of future international multicenter collaborative studies to further increase and standardize the scientific base investigating and treating childhood vasculitis.

Excessive interleukin-15 transpresentation endows NKG2D+CD4+ T cells with innate-like capacity to lyse vascular endothelium in granulomatosis with polyangiitis (Wegener's)

OBJECTIVE

Granulomatosis with polyangiitis (Wegener's) (GPA) is a rare systemic vasculitis of unknown etiology. Contribution of T cell-mediated immunity is suggested by the presence of granulomatous inflammation and T cell infiltrates in different tissues. We undertook this study to determine whether CD4+ T cells aberrantly expressing the NKG2D activating receptor might participate in the pathophysiology of the disease.

METHODS

We performed a detailed phenotype and functional analysis of CD4+ T cells in a cohort of 90 GPA patients (37 with localized GPA and 53 with generalized GPA) in comparison with 39 age-matched controls.

RESULTS

We observed circulating innate-like CD4+ T cells expressing an assortment of activating natural killer (NK) cell receptors (NKG2D, 2B4, DNAX-associated molecule 1, and some killer cell Ig-like receptors) and their signaling partners. Expansions of NKG2D+CD4+ T cells greater than a critical threshold of 3% yielded 100% specificity for generalized vasculitis versus localized granulomatosis, suggesting their participation in endothelium damage. Excessive interleukin-15 (IL-15) transpresentation through increased expression of IL-15 receptor α (IL-15Rα), together with abnormal expression of major histocompatibility complex (MHC) class I chain-related A protein on monocyte/macrophages, induced abnormal expansion of NKG2D+CD4+ T cells. These cells were primed in vivo to exert direct, MHC-independent cytotoxicity toward microvascular endothelial cells expressing the cognate ligands of NK cell receptors.

CONCLUSION

Our results suggest that NK cell-like CD4+ T cells might be the driving force of the vasculitis in GPA, and point to IL-15 as an important mediator in the progression of GPA toward generalized vasculitis. IL-15/IL-15Rα antagonists may thus become novel therapeutic tools to decrease the pool of NK cell receptor-positive CD4+ T cells in selected GPA patients.

T-helper cells as new players in ANCA-associated vasculitides

In anti-neutrophil cytoplasmic autoantibody-associated vasculitides (AAV), several observations support a key role of T-helper cells (CD4(+) T cells) in disease pathophysiology. An expanded population of effector memory CD4(+) T cells in AAV patients may contribute to tissue injury and disease progression. In addition, functional impairment of regulatory T cells (T(Regs)) is reported in AAV patients. A fraction of T(Regs) have the capacity to differentiate into Th17 cells in the context of a proinflammatory environment. Therefore, nonfunctionality of T(Regs) described in AAV patients may be caused by their conversion into IL-17-producing cells that may contribute to granulomatous vasculitis. Further investigations directed at the plasticity of T(Regs) in AAV patients are warranted.

The CD4+CD28null and the regulatory CD4+CD25High T-cell phenotypes in patients with ulcerative colitis during active and quiescent disease, and following colectomy

The CD4+CD25High T-cell phenotype has an essential immunoregulatory role, while the CD4+CD28null T-cell reflects immune pathology. We investigated the profiles of the CD4+CD25High and the CD4+CD28null T-cell phenotypes in patients with ulcerative colitis (UC) during active and quiescent phases as well as following colectomy. Fifty-nine UC patients, 34 active (UCa) and 25 quiescent (UCq) together with 19 healthy controls (HC) were included. Ten of 34 UCa patients underwent colectomy due to unremitting UC (UCo). Immunohistochemical phenotypic of the peripheral blood lymphocytes bearing CD4, CD25 or CD28 was done for analyzes by a multiparameter fluorescence activated cell sorting technique. The expression of the CD4+CD25High phenotype was higher in UCq (P<0.01) or UCo (P<0.01) group vs UCa group. Further, the expression of the CD4+CD28null phenotype in UCa or UCo group was higher than in the HC group (P<0.05). However, the expression of the CD4+CD28null phenotype up to 12 months after colectomy was not significantly different from the levels in the same patients during acute phase. Our impression is that a high CD4+CD25High T-cell reflects alleviation of inflammation, while the expression of the CD4+CD28null T-cell phenotype is an etiologic feature in UC patients, and is maintained after removing the affected colon.

CD4+CD28- T cell expansion in granulomatosis with polyangiitis (Wegener's) is driven by latent cytomegalovirus infection and is associated with an increased risk of infection and mortality

OBJECTIVE

Expanded populations of CD4+CD28- T cells with a cytotoxic phenotype have been repeatedly reported in patients with granulomatosis with polyangiitis (Wegener's) (GPA). In healthy individuals expansion of this T cell population follows cytomegalovirus (CMV) infection. We undertook this study to investigate whether CMV infection may be responsible for driving the expansion of CD4+CD28- T cells in GPA patients and how this might relate to clinical features.

METHODS

Forty-eight GPA patients and 38 age-matched healthy donors were included in the study. CMV-specific IgG in serum was detected by enzyme-linked immunosorbent assay. Flow cytometric analysis was used to study T cell populations and phenotype. The presence of CMV in renal biopsy tissue from GPA patients was investigated by immunohistochemistry and polymerase chain reaction (PCR). Clinical information was obtained from patient records.

RESULTS

Populations of CD4+CD28- T cells were only expanded in CMV-seropositive GPA patients and controls. In CMV-seropositive GPA patients we observed negative correlations between the percentages of CD4+CD28- T cells and both the percentage of naive T cells and the glomerular filtration rate at presentation. There was a significant association between the percentage of CD4+CD28- T cells and risk of infection and mortality. CMV could not be detected in renal tissue by PCR or immunohistochemistry. CMV seropositivity itself was not a risk factor for infection in a cohort of 182 patients with antineutrophil cytoplasmic antibody-associated vasculitis who had been recruited into clinical trials performed by the European Vasculitis Study Group.

CONCLUSION

The expansion of CD4+CD28- T cells in GPA patients is associated with CMV infection and leads to a reduction in the number of naive T cells in peripheral blood. Patients with expanded CD4+CD28- T cells have significantly increased mortality and risk of infection.

CD4+CD28null cells are expanded and exhibit a cytolytic profile in end-stage renal disease patients on peritoneal dialysis

BACKGROUND

End-stage renal failure patients, including those on peritoneal dialysis (PD), exhibit several nontraditional cardiovascular (CV) risk factors. A role of CD4(+)CD28(null) T lymphocytes in the genesis of coronary artery disease (CAD) has been proposed. We investigated this cell population and examined its phenotype in a cohort of PD patients without CV disease.

METHODS

The frequency of the peripheral blood CD4(+)CD28(null) T-cell compartment and cytotoxic characteristic of these cells (as assessed by perforin and granzyme B expressions) were determined in 33 PD patients without CAD and 20 healthy subjects by two- and three-color flowcytometry. High-sensitivity C-reactive protein (hs-CRP) was determined by enzyme-linked immunosorbent assay. We investigated whether there was a correlation between these cells and traditional CV risk factors.

RESULTS

Compared to healthy controls, CD4(+)CD28(null) T cells were significantly expanded in PD patients (10.30 ± 2.03% versus 3.55 ± 0.67%, mean ± SE, P = 0.0007). Perforin and granzyme B expressions were restricted to CD4(+)CD28(null) T cells compared to CD4(+)CD28(+) T cells (<0.0001). A greater proportion of CD4(+)CD28(null) T cells in PD patients expressed these molecules (P = 0.007 and 0.04). hs-CRP level was increased in PD patients (P < 0.0001) but did not correlate with the CD4(+)CD28(null) T-cell frequency. Increasing age correlated with the CD4(+)CD28(null) cells.

CONCLUSIONS

PD patients exhibit a substantially increased number of circulating CD4(+)CD28(null) T cells that show a cytolytic profile before the onset of clinically significant CAD. Their significance as a nontraditional CV risk factor needs further studies.

Recent aspects of vasculitis and future direction

Vasculitis is pathologically identified as specific cellular inflammation, vessel destruction, and tissue necrosis. Current classifications of vasculitis such as the Chapel Hill Classification (CHCC) and American College of Rheumatology (ACR) guidelines are not sufficiently adequate for clinicians to diagnose vasculitis. The biomarkers that are currently in clinical use such as PR3-ANCA and MPO-ANCA, only help in diagnosing small vessel vasculitis and their sensitivity and specificity are not sufficient. However, recent developments related to the pathogenesis and etiopathogenesis of vasculitis have the potential to contribute to new and improved biomarkers. The determination of diverse roles of ANCA and synergistic effects of infection, genetic, environmental factors and drugs on pathogenesis is quite important. The demonstration of a new autoantibody directed to hLAMP-2 and the resemblance to some microbial structures, in addition to the determination of the possible roles of hepatitis B and C on vasculitis are important findings. These hints may lead to new biomarker developments, providing a better method to diagnose vasculitis. The evidence on T cell immunity as circulatory and lesional will likely contribute to the development of new drugs for vasculitis.

Uveitis in DiGeorge syndrome: a case of autoimmune ocular inflammation in a patient with deletion 22q11.2

PURPOSE

Del22q11.2, also known as DiGeorge syndrome, has a spectrum of ocular, facial and systemic features. Despite features of T cell dysfunction, infection and autoimmunity (including juvenile idiopathic arthritis), uveitis has not been described in patients with DiGeorge syndrome.

METHODS

We describe a case of a 25-year-old male with bilateral granulomatous panuveitis who after initial investigation and treatment for an infectious cause was determined to have autoimmune-related uveitis with evidence on clinical, laboratory and imaging assessments suggestive of ocular sarcoidosis.

RESULTS

The patient was found to have a normal T cell count and T cell proliferative response that was compared to a control patient, and phenotypes determined by flow cytometry were normal. However, the CD4/CD8 ratio in this patient was slightly lower than normal and the number of CD28 negative T cells, in both CD4 and CD8 populations, were significantly higher than a control.

CONCLUSIONS

The significance of these T cell abnormalities is unknown in the context of this patient's uveitis but is suggestive of a role in autoimmunity, which is a known phenomenon in del22q11.2 syndrome, although autoimmune-related uveitis is not a previously described feature.

T cells in ANCA-associated vasculitis: what can we learn from lesional versus circulating T cells?

Anti-neutrophil cytoplasmic antibody (ANCA) - associated vasculitis (AAV) is a life-threatening autoimmune disease characterized by an antibody-mediated glomerulonephritis and necrotizing vasculitis. Apart from antibodies, T cells are also involved in disease pathogenesis. This review stresses the hallmarks of T cell-mediated pathology in AAV and highlights the characteristics of lesional and circulating T cells in the immune response in AAV. Circulating effector T-cell populations are expanded and are in a persistent state of activation. Circulating regulatory T-cell subsets are less well characterized but seem to be impaired in function. Lesional effector T cells are present in granulomas, vasculitic lesions, and nephritis. Lesional T cells usually show pro-inflammatory properties and promote granuloma formation. Apart from T cells, dendritic cells are abundantly present at the sites of inflammation and locally orchestrate the immune response. Targeting the above-mentioned T cell-mediated disease mechanisms will potentially provide powerful therapeutic tools for AAV.

Association of Graves' disease and prevalence of circulating IFN-gamma-producing CD28(-) T cells

BACKGROUND

Peripheral blood CD4(+) and CD8(+) T-cell subsets lacking surface CD28 have been suggested to predispose patients to immune-mediated disorders.

MATERIALS AND METHODS

To determine the role of CD28(-) T-cell subset in Graves' disease (GD), we characterized peripheral blood CD4(+)CD28(-) and CD8(+)CD28(-) T cell from early onset GD patients.

RESULTS AND DISCUSSION

GD patients had significantly higher percentages of CD4(+)CD28(-) and CD8(+)CD28(-) T cells than did healthy donors. Both CD28(-) T cells expressed mostly CD45RO, suggesting that they are activated and/or are memory T cells. GD patient-derived CD4(+)CD28(-) and CD8(+)CD28(-) T cells produced more intracellular IFN-gamma than their counterparts from healthy donors. Furthermore, CD4(+)CD28(-) and CD8(+)CD28(-) T cells from GD patients with Graves' ophthalmopathy (GO) secreted higher level of intracellular IFN-gamma than those CD28(-) T cells from GD patients without GO. Retrospective analysis showed that the increased levels of CD4(+)CD28(-) T cells and their IFN-gamma-producing subgroups were positively correlated to the serum anti-thyrotropin receptor (TSHR) autoantibodies (TRAb). Our observations suggest that increased IFN-gamma-producing CD28(-) T cells in GD patients may play an important role in the pathogenesis of GD.

CD28 down-regulation on CD4 T cells is a marker for graft dysfunction in lung transplant recipients

RATIONALE

Repeated antigen-driven proliferations cause CD28 on T cells to down-regulate. We hypothesized that alloantigen-induced proliferations could cause CD28 down-regulation in lung transplant recipients.

OBJECTIVES

To ascertain if CD28 down-regulation on CD4 T cells associated with manifestations of allograft dysfunction in lung transplant recipients.

METHODS

Peripheral blood CD4 T cells from 65 recipients were analyzed by flow cytometry, cytokine multiplex and proliferative assays, and correlated with clinical events.

MEASUREMENTS AND MAIN RESULTS

Findings that CD28 was present on less than 90% of total CD4 T cells were predominantly seen among the recipients with bronchiolitis obliterans syndrome (specificity = 88%). Perforin and granzyme B were produced by >50% of the CD4(+)CD28(null) cells, but less than 6% of autologous CD4(+)CD28(+) cells (P < 0.006). CD4(+)CD28(null) cells also had increased productions of proinflammatory cytokines, but less frequently expressed regulatory T-cell marker FoxP3 (2.1 +/- 1.3%), compared with autologous CD4(+)CD28(+) (9.5 +/- 1.4; P = 0.01). Cyclosporine A (100 ng/ml) inhibited proliferation of CD4(+)CD28(null) cells by 33 +/- 11% versus 68 +/- 12% inhibition of CD4(+)CD28(+) (P = 0.025). FEV(1) fell 6 months later (0.35 +/- 0.04 L) in recipients with CD4(+)CD28(+)/CD4(total) less than 90% (CD28% Low) compared with 0.08 +/- 0.08 L among CD4(+)CD28(+)/CD4(total) (CD28% High) greater than 90% (CD28% High) recipients (P = 0.013). Two-year freedom from death or retransplantation in CD28% Low recipients was 32 +/- 10% versus 78 +/- 6% among the CD28% High subjects (P < 0.0001).

CONCLUSIONS

CD28 down-regulation on CD4 cells is associated with bronchiolitis obliterans syndrome and poor outcomes in lung transplantation recipients. CD4(+)CD28(null) cells have unusual, potentially pathogenic characteristics, and could be important in the progression of allograft dysfunction. These findings may illuminate a novel paradigm of transplantation immunopathogenesis, and suggest that CD28 measurements could identify recipients at risk for clinical deteriorations.

Expansion of circulating NKG2D+ effector memory T-cells and expression of NKG2D-ligand MIC in granulomaous lesions in Wegener's granulomatosis

Expansion of circulating CD28- T-cells reminiscent of effector memory T-cells (T(EM)) has been reported in Wegener's granulomatosis (WG) recently. To investigate the role of T(EM) in WG, we analyzed the expression of the activating NK-receptor NKG2D and its ligand MIC on circulating T(EM) and in granulomatous lesions, respectively. NKG2D was anomalously expressed and preferentially detected on circulating CD4+CD28- T(EM) in WG. Compared to healthy controls, T(EM) display a more activated phenotype potentially favoring unbalanced proinflammatory responses in WG. Cluster-like formations of "Wegener's autoantigen" PR3 were surrounded by NKG2D+ and NKG2D-ligand MIC+ cells in WG-granulomata, but not in disease controls. Further, IL-15 - known to drive T(EM) differentiation and proliferation--was also expressed in WG-granulomata. Thus, through acquisition of NK-like "innate" properties, IL-15 stimulated NKG2D+ T(EM) could interact with MIC+ cells within WG-granulomata, thereby sustaining inflammation and autoimmunity and promoting self-perpetuating pathology in WG.

CD4-Positive Effector Memory T Cells Participate in Disease Expression in ANCA-Associated Vasculitis

Although the cause of ANCA-associated vasculitis (AAV) remains undetermined, the presence of lymphocytic infiltrates in inflammatory lesions of patients suggests that vascular damage is immune mediated. Studies over the past decade have implicated a role for T cells in the pathogenesis of AAV as altered T cell phenotype has been observed in this disorder. The distribution of T cell subpopulations has been analyzed most intensely in Wegener's granulomatosis (WG), where an expanded population of circulating CD4(+) effector memory T cells (CD4(+)T(EM)) was demonstrated. CD4(+)T(EM) cells play a major role in the pathogenesis of several autoimmune diseases. Specific suppression of CD4(+)T(EM) cells inhibits delayed-type hypersensitivity (DTH) and has therapeutic potential in autoimmune disease. Thus, CD4(+)T(EM) cells may act as inducers of tissue injury and participate in the development of AAV. Therapies that target CD4(+)T(EM), without impairing the activity of other lymphocyte subsets, may hold therapeutic promise for AAV.

Immunopathogenesis of sarcoidosis

The immunopathogenesis of sarcoidosis has been difficult to charaterize given the heterogeneity of disease, the elusiveness of the causative antigen, and the lack of an adequate animal model. However, by examining well-defined clinical cohorts, the interplay between genetic predisposition and immunologic response has been increasingly informative. Technological advances in cellular analysis have allowed researchers to characterize the immune responses important in the maintenance of granulomatous inflammation. Finally, "new" clinical observations such as granuloma responsiveness to targeted biological therapies, sarcoid developing during immune restoration, and the relationship between sarcoidosis and Hepatitis C will provide future insight to the immunopathogenesis of sarcoidosis.

Granulomatose de Wegener

Wegener's granulomatosis is described by the Chapel Hill nomenclature (1994) as a systemic necrotizing vasculitis affecting small to medium-sized vessels. Cytoplasm-labeling antineutrophil cytoplasmic autoantibodies (cANCA) directed against proteinase 3 (PR3) are detected in the sera of approximately 90% of patients. Reported incidence varies from 2 to 12 cases/million inhabitants/year and prevalence from 24 to 157 cases/million inhabitants, depending on the series. While still rare, incidence seems to have increased slightly over the past few decades. Most new cases involve adults aged 45-60 years. Many of the immune mechanisms involved in its pathogenesis have been identified. These involve cANCA as well as neutrophils, various lymphocyte subtypes, activation molecules, and cytokines. Genetic and environmental factors have been observed in some cases. However, the precise causes of the disease and of the initial immune process leading to cANCA production remain unknown. The most characteristic clinical manifestations are involvement of the upper and lower respiratory tracts and glomerulonephritis. Diffuse/systemic forms may be clinically distinguished from localized/limited forms: the former are mainly associated with vasculitis, and the latter with granulomatous inflammation. Diagnosis relies largely on the combination of characteristic clinical symptoms and cANCA anti-PR3, but histological confirmation should always be obtained when biopsy of affected organs is feasible and safe. Kidney biopsy is particularly useful in cases with renal manifestations, because it also provides some prognostic information. Current recommendations for treatment of systemic forms call first for an induction phase that combines corticosteroids and intravenous cyclophosphamide; the first three pulses are given every 2 weeks and then every 3 weeks until remission is achieved, followed by a maintenance phase with a less toxic immunosuppressant. The optimal duration of this regimen has not yet been determined, but it must certainly not be less than 18 months. Continuation of cotrimoxazole for two additional years is advised once immunosuppressants have been withdrawn. Remission is obtained in more than 85% of the cases to date, but the high relapse rate remains a matter of concern: approximately half of all patients will relapse within the five years following diagnosis. Promising new therapeutic agents, including rituximab, anti-TNF-alpha, and abatacept, are currently under evaluation and may substantially modify management of this disease in the years to come. Today, however, they are reserved for refractory cases.

Increasing evidence for immune-mediated processes and new therapeutic approaches in abdominal aortic aneurysms--a review

Animal models for abdominal aortic aneurysms (AAAs), immunogenetical and pathophysiological studies support the importance of immune-mediated processes in the pathogenesis of AAA disease. Neutrophils, natural killer (NK) cells, monocytes/macrophages, and proinflammatory cytokines are involved in the complex and dynamic tissue remodeling of the AAA vessel wall. Our group showed an increased prevalence of circulating interferon-gamma (IFN-gamma) producing CD28(-) T cells especially in smaller AAAs, thus supporting the concept of a T cell-mediated pathophysiology of AAAs, especially during the early development of AAAs. Further research should now assess the possible benefit of anti-inflammatory therapeutic approaches in AAA patients, especially with small AAAs.