Diagnosis and classification of eosinophilic granulomatosis with polyangiitis (formerly named Churg–Strauss syndrome)

Recently, a group of experts in the field suggested to rename Churg–Strauss syndrome as eosinophilic granulomatosis with polyangiitis (EGPA). This condition, first described in 1951, is a rare small- and medium-sized–vessel vasculitis characterized by an almost constant association with asthma and eosinophilia, and, by the presence of anti-myeloperoxidase (MPO) antineutrophil cytoplasm antibodies (ANCA) in 30–38% of the patients. Vasculitis typically develops in a previously asthmatic and eosinophilic middle-aged patient. Asthma is severe, associated with eosinophilia and extrapulmonary symptoms. Most frequently EGPA involves the peripheral nerves and skin. Other organs, however, may be affected and must be screened for vasculitis, especially those associated with a poorer prognosis, such as the heart, kidney and gastrointestinal tract, as assessed by the recently revised Five-Factor Score (FFS). Recent insights, particularly concerning clinical differences associated with ANCA status, showed that EGPA patients might constitute a heterogeneous group. Thus, EGPA patients with anti-MPO ANCA suffered more, albeit not exclusively, from vasculitis symptoms, such as glomerulonephritis, mononeuritis multiplex and alveolar hemorrhage, whereas ANCA-negative patients more frequently develop heart involvement. This observation led to the hypothesis that EGPA might be divided into different clinical and pathophysiological subtypes, which could be managed better with more specifically adapted therapies.For now, EGPA treatment still relies mainly on corticosteroids and, when necessary for patients with poorer prognoses, combined immunosuppressant drugs, especially cyclophosphamide. Overall survival of EGPA patients is good, despite not uncommon relapses.     

The histological assessment of cutaneous vasculitis

Carlson J A
(2010) Histopathology 56, 3–23
The histological assessment of cutaneous vasculitis Vasculitis is defined as inflammation directed at vessels, which compromises or destroys the vessel wall leading to haemorrhagic and/or ischaemic events. Skin biopsy is the gold standard for the diagnosis of cutaneous vasculitis, whose manifestations include urticaria, infiltrative erythema, petechiae, purpura, purpuric papules, haemorrhagic vesicles and bullae, nodules, livedo racemosa, deep (punched out) ulcers and digital gangrene. These varied morphologies are a direct reflection of size of the vessels and extent of the vascular bed affected, ranging from a vasculitis affecting few superficial, small vessels in petechial eruptions to extensive pan‐dermal small vessel vasculitis in haemorrhagic bullae to muscular vessel vasculitis in lower extremity nodules with livedo racemosa. Skin biopsy, extending to subcutis and taken from the earliest, most symptomatic, reddish or purpuric lesion is crucial for obtaining a high‐yielding diagnostic sample. Based on histology, vasculitis can be classified on the size of vessels affected and the dominant immune cell mediating the inflammation (e.g. neutrophilic, granulomatous, lymphocytic, or eosinophilic). Disruption of small vessels by inflammatory cells, deposition of fibrin within the lumen and/or vessel wall coupled with nuclear debris allows for the confident recognition of small vessel, mostly neutrophilic vasculitis (also known as leukocytoclastic vasculitis). In contrast, muscular vessel vasculitis can be identified solely by infiltration of its wall by inflammatory cells. Extravasation of red blood cells (purpura) and necrosis are supportive, but not diagnostic of vasculitis as they are also seen in haemorrhagic and/or vaso‐occlusive disorders (pseudovasculitis). Vasculitic foci associated with extravascular granulomas (palisaded neutrophilic and granulomatous dermatitis), tissue eosinophilia, or tissue neutrophilia signal the risk for, or co‐existence of systemic disease. This essential histological information coupled with direct immunofluorescence and anti‐neutrophil cytoplasmic data and clinical findings enables more precise and accurate diagnosis of localized and systemic vasculitis syndromes.     

IL‐6: Regulator of Treg/Th17 balance

IL‐6 is a pleiotropic cytokine involved in the physiology of virtually every organ system. Recent studies have demonstrated that IL‐6 has a very important role in regulating the balance between IL‐17‐producing Th17 cells and regulatory T cells (Treg). The two T‐cell subsets play prominent roles in immune functions: Th17 cell is a key player in the pathogenesis of autoimmune diseases and protection against bacterial infections, while Treg functions to restrain excessive effector T‐cell responses. IL‐6 induces the development of Th17 cells from naïve T cells together with TGF‐β; in contrast, IL‐6 inhibits TGF‐β‐induced Treg differentiation. Dysregulation or overproduction of IL‐6 leads to autoimmune diseases such as multiple sclerosis (MS) and rheumatoid arthritis (RA), in which Th17 cells are considered to be the primary cause of pathology. Given the critical role of IL‐6 in altering the balance between Treg and Th17 cells, controlling IL‐6 activities is potentially an effective approach in the treatment of various autoimmune and inflammatory diseases. Here, we review the role of IL‐6 in regulating Th17/Treg balance and describe the critical functions of IL‐6 and Th17 in immunity and immune‐pathology.     

IL-13-producing Th1 and Th17 cells characterize adaptive responses to both self and foreign antigens

In helper T cells, IL‐13 is traditionally considered a Th2‐type cytokine that is coexpressed with IL‐4. Using mouse models of immunization and autoimmunity, we demonstrate that IL‐13 is frequently uncoupled from IL‐4, and that it can be produced by both IFN‐γ⁺ Th1 cells and IL‐17⁺ Th17 cells. We report that these IL‐13‐producing Th1 and Th17 cells are distinct from classical IL‐4⁺ Th2 cells and that they are relatively common, appearing in the context of both protective and pathogenic T‐cell responses. We also demonstrate that IL‐13 and Th2‐type cytokines can have important consequences in Th1‐ and Th17‐dominated settings, such as lymphopenia‐induced autoimmune disease, where they can be either pro‐ or anti‐inflammatory, depending on whether they act on innate or adaptive immune cells. Taken together, our studies indicate that IL‐13 production is more widespread than previously appreciated and that blocking this cytokine may have therapeutic benefits even in settings where traditional IL‐4‐driven Th2‐type responses are not evident.     

IL‐23 in the Pathogenesis of Rheumatoid Arthritis

Interleukin‐23 (IL‐23) is a heterodimeric cytokine belonging to the IL‐6/IL‐12 family that plays a key role in several of autoimmune and inflammatory disorders. This family contains the 34 type I cytokine receptor chains and 27 ligands, which share structural and functional similarities, but on the other hand they display distinct roles in shaping Th cells responses. IL‐12 family cytokines have not only proinflammatory effects but they also promote inflammatory responses. IL‐23 is composed of the p40 subunit in common with IL‐12, and with a unique p19 subunit. IL‐23 binding to an IL‐23 receptor expressed on dendritic cells, macrophages and monocytes triggers the activation of Jak2 and Tyk2, which in turn phosphorylates STAT1, STAT3, STAT4 and STAT5 as well as induce formation of STAT3‐STAT4 heterodimers. IL‐23 is one of the essential factors required for the survival and/or expansion of Th17 cells, which produce IL‐17, IL‐17F, IL‐6 and TNF‐α. Th17 cells stimulated by the IL‐23 promote osteoclastogenesis through production of IL‐17, which induce receptor activator of NF‐kappa B ligand on mesenchymal cells. The IL‐23‐IL‐17 axis includes Th17 cells and plays a key role in the development of autoimmune arthritis.     

Intestinal helminth infection induces highly functional resident memory CD4+ T cells in mice

Immunity to intestinal nematodes requires CD4? Th2‐cell responses, including IL‐4 and IL‐13 production. Chronic infection with intestinal nematodes leads to downregulation of these responses, and few functional T helper (Th) 2 cells are detected in secondary lymphoid organs in the chronic phase or after abrogation of infection. Here, we show with a natural murine infection with Heligmosomoides polygyrus that highly functional memory Th2 cells persist in the lamina propria and in addition in the peritoneal cavity (PC) after abrogation of infection. While both tissue‐resident memory (T_RM) populations proliferate in situ and express IL‐4, IL‐5, and IL‐13 upon TCR‐dependent stimulation, only peritoneal memory cells express high levels of the IL‐33 receptor and produce IL‐5 and IL‐13 upon TCR‐independent stimulation with IL‐33 and IL‐7. Most importantly, PC‐derived T_RM cells are able to mediate anti‐helminthic effects by decreasing the fecundity of female worms upon transfer into recipient mice. These results show that nonlymphoid compartments can serve as reservoirs for Th2 memory cells, and furthermore that innate effector function of Th2 memory cells is restricted to CD4? memory T cells residing in the PC.     

Antigen presenting cell‐derived IL‐6 restricts Th2‐cell differentiation

The identification of DC‐derived signals orchestrating activation of Th1 and Th17 immune responses has advanced our understanding on how these inflammatory responses develop. However, whether specific signals delivered by DCs also participate in the regulation of Th2 immune responses remains largely unknown. In this study, we show that administration of antigen‐loaded, IL‐6‐deficient DCs to naïve mice induced an exacerbated Th2 response, characterized by the differentiation of GATA‐3‐expressing T lymphocytes secreting high levels of IL‐4, IL‐5, and IL‐13. Coinjection of wild type and IL‐6‐deficient bone marrow‐derived dendritic cells (BMDCs) confirmed that IL‐6 exerted a dominant, negative influence on Th2‐cell development. This finding was confirmed in vitro, where exogenously added IL‐6 was found to limit IL‐4‐induced Th2‐cell differentiation. iNKT cells were required for optimal Th2‐cell differentiation in vivo although their activation occurred independently of IL‐6 secretion by the BMDCs. Collectively, these observations identify IL‐6 secretion as a major, unsuspected, mechanism whereby DCs control the magnitude of Th2 immunity.     

Eosinophilic granulomatosis with polyangiitis: the multifaceted spectrum of clinical manifestations at different stages of the disease

ABSTRACT

Introduction: Eosinophilic granulomatosis with polyangiitis (EGPA) usually occurs in patients with late-onset asthma and sustained peripheral blood eosinophilia and classically presents with a clinical multifaceted spectrum of manifestations, which may vary at the different stages of the natural history of the disease.

Areas covered: We reviewed EGPA clinical presentation, focusing on clinical manifestations at three different phases of the disease: 1/before the development of overt vasculitis, 2/at vasculitis diagnosis and 3/during the long-term follow-up. An update on current classification criteria and recent therapeutic advances has been provided as well.

Expert opinion: Asthma, chronic rhinosinusitis and blood eosinophilia could anticipate the overt vasculitis for years. An atopic background may be present in a subset of patients (25-30%), while ANCA presence varies between 10 and 40%. Systemic vasculitis rapidly occurs and clinical features demonstrating vasculitis processes (neuropathy, purpura, scleritis, alveolar hemorrhage and glomerulonephritis) develop along with systemic symptoms (50%). After vasculitis resolution, asthma remains severe in up to 50% of patients and incidence of isolated-asthma and rhinosinus exacerbations remains constantly high. Different sets of classification criteria have been published so far, and DCVAS diagnostic criteria will be presented soon. Interleukin-5 blockers seem to be promising to control the disease and to spare corticosteroids.     

Boswellic acids reduce Th17 differentiation via blockade of IL‐1β‐mediated IRAK1 signaling

Interferon‐gamma producing CD4⁺ T (Th1) cells and IL‐17‐producing CD4⁺ T (Th17) cells are involved in the pathogenesis of several autoimmune diseases including multiple sclerosis. Therefore, the development of treatment strategies controlling the generation and expansion of these effector cells is of high interest. Frankincense, the resin from trees of the genus Boswellia, and particularly its prominent bioactive compound acetyl‐11‐keto‐β‐boswellic acid (AKBA), have potent anti‐inflammatory properties. Here, we demonstrate that AKBA is able to reduce the differentiation of human CD4⁺ T cells to Th17 cells, while slightly increasing Th2‐ and Treg‐cell differentiation. Furthermore, AKBA reduces the IL‐1β‐triggered IL‐17A release of memory Th17 cells. AKBA may affect IL‐1β signaling by preventing IL‐1 receptor‐associated kinase 1 phosphorylation and subsequently decreasing STAT3 phosphorylation at Ser727, which is required for Th17‐cell differentiation. The effects of AKBA on Th17 differentiation and IL‐17A release make the compound a good candidate for potential treatment of Th17‐driven diseases.     

Pathogenesis of Churg–Strauss syndrome: Recent insights

Churg–Strauss syndrome (CSS) is a rare systemic necrotizing vasculitis associated with granuloma formation and severe blood and tissue eosinophilia. CSS occurs almost exclusively in patients with asthma. Its pathogenesis remains largely unknown, as triggering factors for CSS development have not been identified so far. AAb, such as anti-neutrophil cytoplasmic autoantibodies, are found in less than half of patients and possibly constitute a subtype of CSS with different clinical behaviour. On a cellular level, CSS is characterized by a strong Th2-type immune response. Th2-associated cytokines such as IL-4, IL-13 and IL-5 may precipitate the severe eosinophilia in CSS, while migration of Eos to inflammatory sites is possibly mediated by eotaxin-3. This review summarizes recent advances in the knowledge on epidemiology, clinical features, and pathogenesis of CSS.     

Tim‐3 regulates inflammatory cytokine expression and Th17 cell response induced by monocytes from patients with chronic hepatitis B

Tim‐3 is expressed on monocytes/macrophages and is involved in the regulation of inflammatory responses. The aim of this study was to determine the effect of Tim‐3 on inflammatory response triggered by peripheral monocytes from patients with chronic hepatitis B (CHB). Tim‐3 expression on peripheral monocytes and frequency of Th17 cells in peripheral blood mononuclear cells (PBMCs) derived from CHB patients were detected. Followed by lipopolysaccharides (LPS) activation of circulating monocytes from CHB patients, expression of inflammatory cytokines including TNF‐α，IL‐1β and IL‐6 were examined in the presence and absence of Galectin‐9 which is the ligand for Tim‐3. Subsequently, after purified CD4+T cells were cocultured with LPS‐activated monocytes from CHB patients in the presence of anti‐Tim‐3 antibody, percentage of Th17 cells and production of IL‐17 were measured. Tim‐3 expression was significantly upregulated and closely correlated to the frequency of Th17 cells in patients with CHB. Expression of TNF‐α，IL‐1β and IL‐6 increased significantly in monocytes stimulated with LPS and Galectin‐9, compared to LPS stimulation alone. LPS‐activated monocytes from CHB patients could drive differentiation of memory CD4+T cells to Th17 cells. However, under the blockade of Tim‐3 signalling by anti‐Tim‐3 antibody, percentage of Th17 cells and production of IL‐17 decreased significantly. Our results demonstrate that upregulated expression of Tim‐3 on circulating monocytes accelerates inflammatory response by promoting production of inflammatory cytokines and Th17 responses in CHB.     

Th17 response and its regulation in inflammatory upper airway diseases

Allergic rhinitis (AR) and chronic rhinosinusitis (CRS) are two widely prevalent inflammatory diseases in the upper airways. T cell immunity has been suggested to play an important pathogenic role in many chronic inflammatory diseases including inflammatory upper airway diseases. Inappropriate CD4⁺ T cell responses, especially the dysregulation of the Th1/Th2 balance leading to excessive Th1 or Th2 cell activation, have been associated with allergic rhinitis and chronic rhinosinusitis. Nevertheless, recent studies suggest that IL‐17A and IL‐17A‐producing Th17 cell subset, a distinct pro‐inflammatory CD4⁺ T cell lineage, may also play an important role in the pathophysiology of inflammatory upper airway diseases. Th17 cells may promote both eosinophilic and neutrophilic inflammation in AR and CRS. In addition, a few, but accumulating evidence shows that the Th17 responses can be tightly regulated by endogenous and exogenous substances in the context of AR and CRS. This review discusses recent advances in our understanding of the expression and function of the Th17 response and its regulation in inflammatory upper airway diseases, and the perspective for future investigation and clinical utility.     

Effects of Pregnancy‐associated Malaria on T Cell Cytokines in Cameroonian Women

Although Th17 cells subsets improve immunity against extra and intracellular pathogens, and in modulating Th1 and other immune responses, its role on pregnancy‐associated malaria (PAM) is unknown. This study aims to investigate the effects of PAM on Th1 (IFN‐γ, TNF‐α), IL‐10 family (IL‐10, IL‐19, IL‐22), Th17 (IL‐17A, IL‐23) cytokines and on CXCL‐10 chemokine profiles in pregnant women. Between 2010 and 2011, venous blood specimens from 107 volunteer pregnant Cameroonian women was used to determine parasitaemia microscopically and haemoglobin levels using HemoCue analyzer. Plasma levels of the biomarkers were determined by ELISA. Parasitaemia was higher in women with low haemoglobin levels, parity and mother's age. IL‐10 and CXCL‐10 plasma levels were higher in the malaria infected and in anaemic women while IFN‐γ and IL‐17A levels were higher in malaria non‐infected and in non‐anaemic women. Parasitaemia correlated positively with IL‐10 and CXCL‐10 levels but inversely with IFN‐γ and IL‐17A. Haemoglobin levels were higher in women with low IL‐10 and CXCL‐10 levels, and in group with high IFN‐γ, IL‐17A and IL‐23 levels. Only IL‐10 levels associated negatively with parity. Positive correlations were observed between Th17 (IL‐17A) and Th1 (IFN‐γ, TNF‐α), IL‐10 family (IL‐19 and IL‐22) and Th17 (IL‐23) cytokines. Multivariate analysis showed association between: mother's age and IFN‐γ levels, parasitaemia and IL‐10 and CXCL‐10 levels and haemoglobin levels, gestational age and IL‐17A levels. In conclusion, during PAM, CXCL‐10 and IL‐10 responses are implicated in the pathogenesis while Th17 and Th1 immune responses, via IL‐17A and IFN‐γ might play protective roles.     

Mycobacterium tuberculosis RpfE promotes simultaneous Th1‐ and Th17‐type T‐cell immunity via TLR4‐dependent maturation of dendritic cells

Reciprocal induction of the Th1 and Th17 immune responses is essential for optimal protection against Mycobacterium tuberculosis (Mtb); however, only a few Mtb antigens are known to fulfill this task. A functional role for resuscitation‐promoting factor (Rpf) E, a latency‐associated member of the Rpf family, in promoting naïve CD4⁺ T‐cell differentiation toward both Th1 and Th17 cell fates through interaction with dendritic cells (DCs) was identified in this study. RpfE induces DC maturation by increasing expression of surface molecules and the production of IL‐6, IL‐1β, IL‐23p19, IL‐12p70, and TNF‐α but not IL‐10. This induction is mediated through TLR4 binding and subsequent activation of ERK, p38 MAPKs, and NF‐κB signaling. RpfE‐treated DCs effectively caused naïve CD4⁺ T cells to secrete IFN‐γ, IL‐2, and IL‐17A, which resulted in reciprocal expansions of the Th1 and Th17 cell response along with activation of T‐bet and RORγt but not GATA‐3. Furthermore, lung and spleen cells from Mtb‐infected WT mice but not from TLR4^?/? mice exhibited Th1 and Th17 polarization upon RpfE stimulation. Taken together, our data suggest that RpfE has the potential to be an effective Mtb vaccine because of its ability to activate DCs that simultaneously induce both Th1‐ and Th17‐polarized T‐cell expansion.     

Human mucosal leishmaniasis: Neutrophils infiltrate areas of tissue damage that express high levels of Th17‐related cytokines

Mucosal leishmaniasis (ML) is characterised by severe tissue destruction. Herein, we evaluated the involvement of the IL‐17‐type response in the inflammatory infiltrate of biopsy specimens from 17 ML patients. IL‐17 and IL‐17‐inducing cytokines (IL‐1β, IL‐23, IL‐6 and TGF‐β) were detected by immunohistochemistry in ML patients. IL‐17⁺ cells exhibited CD4⁺, CD8⁺ or CD14⁺ phenotypes, and numerous IL‐17⁺ cells co‐expressed the CC chemokine receptor 6 (CCR6). Neutrophils, a hallmark of Th17‐mediated inflammation, were regularly detected in necrotic and perinecrotic areas and stained positive for neutrophil elastase, myeloperoxidase and MMP‐9. Taken together, these observations demonstrate the existence of Th17 cells in ML lesions associated with neutrophils in areas of tissue injury and suggest that IL‐17 is involved in ML pathogenesis.     

The vaccine adjuvant alum inhibits IL‐12 by promoting PI3 kinase signaling while chitosan does not inhibit IL‐12 and enhances Th1 and Th17 responses

Alum is the principal vaccine adjuvant for clinical applications but it is a poor inducer of cellular immunity and is not an optimal adjuvant for vaccines where Th1 responses are required for protection. The mechanism underlying the inefficiency of alum in promoting Th1 responses is not fully understood. We show that aluminium hydroxide, aluminium phosphate, and calcium phosphate adjuvants inhibit the secretion of the Th1 polarizing cytokine, IL‐12 by dendritic cells (DCs). Alum selectively inhibited DC expression of the IL‐12p35 subunit and the inhibitory effect results from adjuvant‐induced PI3 kinase signaling. To develop a more effective adjuvant for promoting cell‐mediated immunity, we investigated alternative particulates and found that in contrast to alum, the cationic polysaccharide chitosan did not inhibit IL‐12 secretion. A combination of chitosan and the TLR9 agonist CpG activated the NLRP3 inflammasome and enhanced secretion of IL‐12 and the other key Th1 and Th17‐cell polarizing cytokines. When used as an adjuvant, CpG‐chitosan induced NLRP3‐dependent antigen‐specific Th1 and Th17 responses. A combination of alum and CpG also enhanced Th1 and Th17 responses but was less effective than CpG‐chitosan. Therefore, chitosan is an attractive alternative to alum in adjuvants for vaccines where potent cell‐mediated immunity is required.     

OX40 blockade inhibits house dust mite driven allergic lung inflammation in mice and in vitro allergic responses in humans

The costimulatory receptor OX40 is expressed on activated T cells and regulates T‐cell responses. Here, we show the efficacy and mechanism of action of an OX40 blocking antibody using the chronic house dust mite (HDM) mouse model of lung inflammation and in vitro HDM stimulation of cells from HDM allergic human donors. We have demonstrated that OX40 blockade leads to a reduction in the number of eosinophils and neutrophils in the lavage fluid and lung tissue of HDM sensitized mice. This was accompanied by a decrease in activated and memory CD4⁺ T cells in the lungs and further analysis revealed that both the Th2 and Th17 populations were inhibited. Improved lung function and decreased HDM‐specific antibody responses were also noted. Significantly, efficacy was observed even when anti‐OX40 treatment was delayed until after inflammation was established. OX40 blockade also inhibited the release of the Th2 cytokines IL‐5 and IL‐13 from cells isolated from HDM allergic human donors. Altogether, our data provide evidence of a role of the OX40/OX40L pathway in ongoing allergic lung inflammation and support clinical studies of a blocking OX40 antibody in Th2 high severe asthma patients.