Kanade Shinkai

Type 2 Immunity Reflects Orchestrated Recruitment of Cells Committed to IL-4 Production

Using IL-4 reporter mice we identified eosinophils, basophils, and Th2 cells as the three IL-4-producing cell types that appear in the lungs of mice infected with the migrating intestinal helminth, Nippostrongylus brasiliensis. Eosinophils were most prevalent, peaking by approximately 1000-fold on day 9 after infection, with Th2 cells and basophils at 3- and 10-fold lower numbers, respectively. Eosinophil and basophil expansion in blood in response to parasites and their capacity for IL-4 expression required neither Stat6 nor T cells. Th2 induction and expansion in draining lymph nodes was also Stat6 independent. In contrast, eosinophil (and Th2 cell) recruitment to the lung was dependent on Stat6 expression by a bone marrow-derived tissue resident cell, whereas basophil recruitment was Stat6 and IL-4/IL-13 independent but T cell dependent. Primary type 2 immune responses in the lung represent the focal recruitment and activation of discrete cell populations from the blood that have previously committed to express IL-4.

Analysis of Type 2 Immunity In Vivo with a Bicistronic IL-4 Reporter

Effector T cells mediate adaptive immunity and immunopathology, but methods for tracking such cells in vivo are limited. We engineered knockin mice expressing IL-4 linked via a viral IRES element with enhanced green fluorescent protein (EGFP). Reporter T cells primed under Th2 conditions showed sensitive and faithful EGFP expression and maintained endogenous IL-4. After Nippostrongylus infection, reporter expression demonstrated the evolution of type 2 immunity from tissue lymphocytes and thence to lymph node CD4(+) T cells, which subsequently migrated into tissue. The appearance of EGFP(+) CD4(+) T cells in tissue, but not in lymph nodes, was Stat6-dependent. Transferred EGFP(+) CD4(+) T cells from infected animals conferred protection against Nippostrongylus to immunodeficient mice. These mice will provide a valuable reagent for assessing immunity in vivo.

Impaired NFATc Translocation and Failure of Th2 Development in Itk-Deficient CD4+ T Cells

Naive Itk-deficient CD4+ T cells were unable to establish stable IL-4 production, even when primed in Th2-inducing conditions. In contrast, IFNgamma production was little affected. Failure to express IL-4 occurred even among cells that had gone through multiple cell divisions and was associated with a delay in the kinetics and magnitude of NFATc nuclear localization. IL-4 production was restored genetically by retroviral reconstitution of Itk or biochemically by augmenting the calcium flux with ionomycin. In vivo, Itk-deficient mice were unable to establish functional Th2 cells. Development of protective Th1 cells was unimpeded. These data define a nonredundant role for Itk in modulating signals from the TCR/CD28 pathways that are specific for the establishment of stable IL-4 but not IFNgamma expression.

Type 2 immunity is controlled by IL-4/IL-13 expression in hematopoietic non-eosinophil cells of the innate immune system

Nippostrongylus brasiliensis infection and ovalbumin-induced allergic lung pathology are highly interleukin (IL)-4/IL-13 dependent, but the contributions of IL-4/IL-13 from adaptive (T helper [Th]2 cells) and innate (eosinophil, basophils, and mast cells) immune cells remain unknown. Although required for immunoglobulin (Ig)E induction, IL-4/IL-13 from Th2 cells was not required for worm expulsion, tissue inflammation, or airway hyperreactivity. In contrast, innate hematopoietic cell–derived IL-4/IL-13 was dispensable for Th2 cell differentiation in lymph nodes but required for effector cell recruitment and tissue responses. Eosinophils were not required for primary immune responses. Thus, components of type 2 immunity mediated by IL-4/IL-13 are partitioned between T cell–dependent IgE and an innate non-eosinophil tissue component, suggesting new strategies for interventions in allergic immunity.

Activation of a Nonclassical NKT Cell Subset in a Transgenic Mouse Model of Hepatitis B Virus Infection

NKT cells are specialized cells of the immune system that bear both T cell and NK cell markers. Classical NKT cells display TCRs of restricted heterogeneity (Valpha14-Jalpha281) and recognize lipid antigens (e.g., alpha-galactosyl ceramide) presented by nonpolymorphic CD1 molecules. Recently, other nonclassical NKT subsets have been recognized, including NKT cells not reactive with CD1d-alpha-galactosyl ceramide complexes. The biological functions of these cells are unknown. Here, we show that nonclassical NKT cells that are CD1d restricted but nonreactive to alpha-GalCer are activated in response to hepatocytes expressing hepatitis B viral antigens in a transgenic mouse model of acute hepatitis B virus infection. Our results document the first in vivo function for such nonclassical NKT cells and suggest a role for these cells in the host response to HBV infection.

Deletion of a coordinate regulator of type 2 cytokine expression in mice

Mechanisms that underlie the patterning of cytokine expression in T helper (TH) cell subsets remain incompletely defined. An evolutionarily conserved ∼400-bp noncoding sequence in the intergenic region between the genes Il4 and Il13, designated conserved noncoding sequence 1 (CNS-1), was deleted in mice. The capacity to develop TH2 cells was compromised in vitro and in vivo in the absence of CNS-1. Despite the profound effect in T cells, mast cells from CNS-1−/− mice maintained their capacity to produce interleukin 4. A T cell–specific element critical for the optimal expression of type 2 cytokines may represent the evolution of a regulatory sequence exploited by adaptive immunity.

Helper T cells regulate type-2 innate immunity in vivo

Type-2 immunity requires orchestration of innate and adaptive immune responses to protect mucosal sites from pathogens. Dysregulated type-2 responses result in allergy or asthma. T helper 2 (TH2) cells elaborate cytokines, such as interleukin (IL)-4, IL-5, IL-9 and IL-13, which work with toxic mediators of innate immune cells to establish environments that are inhospitable to helminth or arthropod invaders. The importance of TH2 cells in coordinating innate immune cells at sites of inflammation is not known. Here we show that polarized type-2 immune responses are initiated independently of adaptive immunity. In the absence of B and T cells, IL-4-expressing eosinophils were recruited to tissues of mice infected with the helminth Nippostrongylus brasiliensis, but eosinophils failed to degranulate. Reconstitution with CD4 T cells promoted accumulation of degranulated IL-4-expressing cells, but only if T cells were stimulated with cognate antigen. Degranulation correlated with tissue destruction, which was attenuated if eosinophils were depleted. Helper T cells confer antigen specificity on eosinophil cytotoxicity, but not cytokine responses, so defining a novel mechanism that focuses tissue injury at sites of immune challenge.

Etiology and Management of Pyoderma Gangrenosum

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis characterized by painful, necrotic ulceration. It typically affects patients in the third to sixth decades of life, with almost equal incidence in men and women. PG occurs most frequently on the lower extremities. Five clinical variants are currently recognized: classic, bullous, pustular, vegetative, and peristomal types. Half of PG cases are seen in association with systemic disease. Mimickers include infection, vascular insufficiency ulcers, systemic vasculitides, autoimmune disease, cancer, and exogenous tissue injury, among others. PG is often a diagnosis of exclusion, as there are no specific laboratory or histopathologic findings to confirm the diagnosis. PG thus presents many clinical challenges: it is difficult to diagnose, is frequently misdiagnosed, and often requires a work-up for underlying systemic disease. Successful management of PG typically requires multiple modalities to reduce inflammation and optimize wound healing, in addition to treatment of any underlying diseases. Prednisone and cyclosporine have been mainstays of systemic treatment for PG, although increasing evidence supports the use of biologic therapies, such as tumor necrosis factor-a inhibitors, for refractory cases of PG. Here, we review the clinical presentation and pathophysiology of PG, as well as its associated conditions, diagnostic work-up, and management.

Cryopyrin-associated periodic syndromes and autoinflammation.

Autoinflammatory syndromes are a distinct class of inherited diseases of cytokine dysregulation with important cutaneous features. Several disorders, including familial cold autoinflammatory syndrome (FCAS), Muckle–Wells syndrome and neonatal onset multisystem inflammatory disorder (NOMID), are associated with mutations in a common gene, CIAS‐1. These disorders are now believed to represent related conditions along a spectrum of disease severity, in which FCAS is the mildest and NOMID is the most severe phenotype. Patients typically present with lifelong atypical urticaria with systemic symptoms, with potential for developing end‐organ damage due to chronic inflammation. Advances in the understanding of the genetic basis of these syndromes have also revealed cytokine signalling molecules that are critical to normal regulation of inflammatory pathways. The dramatic response of these syndromes to anakinra, an interleukin (IL)‐1 antagonist, highlights the important role of IL‐1 cytokine signalling in the pathogenesis of this rare but fascinating class of diseases.

Hidradenitis Suppurativa and Concomitant Pyoderma Gangrenosum A Case Series and Literature Review

BACKGROUND Hidradenitis suppurativa (HS) and pyoderma gangrenosum (PG) are both rare inflammatory skin conditions that are associated with systemic inflammatory diseases. We performed a retrospective medical chart review of patients with an overlap of HS and PG. OBSERVATIONS We identified 11 cases of PG lesions presenting in patients with HS. Ten of the patients were women, and 9 were obese. All the patients developed HS lesions first, a median of 2.5 years (range, 0-15 years) preceding the appearance of PG lesions. All patients required multiple therapeutic agents because their diseases were often poorly responsive to standard therapies. Two patients received tumor necrosis factor inhibitors; 1 responded to treatment. One patient was treated with anakinra (interleukin-1 receptor antagonist) and had a 75% improvement of her lesions. CONCLUSIONS We have identified a group of patients who have an overlap of PG and HS. Pyoderma gangrenosum can appear at any point after the development of HS and often has a severe, refractory course. We propose that PG and HS may represent variant manifestations of cytokine dysregulation by the innate immune system with common etiology. New therapeutic agents are eagerly sought, and further investigation with regard to interleukin 1 blockade is warranted.