Mechanical Skin Injury Promotes Food Anaphylaxis by Driving Intestinal Mast Cell Expansion.

Mast cell (MC) mediator release after crosslinking of surface-bound IgE antibody by ingested antigen underlies food allergy. However, IgE antibodies are not uniformly associated with food allergy, and intestinal MC load is an important determinant. Atopic dermatitis (AD), characterized by pruritis and cutaneous sensitization to allergens, including foods, is strongly associated with food allergy. Tape stripping mouse skin, a surrogate for scratching, caused expansion and activation of small intestinal MCs, increased intestinal permeability, and promoted food anaphylaxis in sensitized mice. Tape stripping caused keratinocytes to systemically release interleukin-33 (IL-33), which synergized with intestinal tuft-cell-derived IL-25 to drive the expansion and activation of intestinal type-2 innate lymphoid cells (ILC2s). These provided IL-4, which targeted MCs to expand in the intestine. Duodenal MCs were expanded in AD. In addition to promoting cutaneous sensitization to foods, scratching may promote food anaphylaxis in AD by expanding and activating intestinal MCs.

Mast cell-derived IL-13 downregulates IL-12 production by skin dendritic cells to inhibit the TH1 cell response to cutaneous antigen exposure.

BACKGROUND: Atopic dermatitis (AD) is characterized by a skin barrier defect aggravated by mechanical injury inflicted by scratching, a TH2 cell-dominated immune response, and susceptibility to viral skin infections that are normally restrained by a TH1 cell response. The signals leading to a TH2 cell-dominated immune response in AD are not completely understood. OBJECTIVE: Our aim was to determine the role of IL-13 in initiation of the TH cell response to cutaneously encountered antigens. METHODS: Wild-type, Il13-/-, Il1rl1-/-, and Il4ra-/- mice, as well as mice with selective deficiency of IL-13 in mast cells (MCs) were studied; in addition, dendritic cells (DCs) purified from the draining lymph nodes of tape-stripped and ovalbumin (OVA)-sensitized skin were examined for their ability to polarize naive OVA-TCR transgenic CD4+ T cells. Cytokine expression was examined by reverse-transcriptase quantitative PCR, intracellular flow cytometry, and ELISA. Contact hypersensitivity to dinitrofluorobenzene was examined. RESULTS: Tape stripping caused IL-33-driven upregulation of Il13 expression by skin MCs. MC-derived IL-13 acted on DCs from draining lymph nodes of OVA-sensitized skin to selectively suppress their ability to polarize naive OVA-TCR transgenic CD4+ T cells into IFN-γ-secreting cells. MC-derived IL-13 inhibited the TH1 cell response in contact hypersensitivity to dinitrofluorobenzene. IL-13 suppressed IL-12 production by mouse skin-derived DCs in vitro and in vivo. Scratching upregulated IL13 expression in human skin, and IL-13 suppressed the capacity of LPS-stimulated human skin DCs to express IL-12 and promote IFN-γ secretion by CD4+ T cells. CONCLUSION: Release of IL-13 by cutaneous MCs in response to mechanical skin injury inhibits the TH1 cell response to cutaneous antigen exposure in AD.

ILC2 activation by keratinocyte-derived IL-25 drives IL-13 production at sites of allergic skin inflammation.

BACKGROUND: Atopic dermatitis skin lesions demonstrate increased expression of IL-25 by keratinocytes and increased numbers of type 2 innate lymphoid cells (ILC2s) that express high levels of IL-25 receptor (IL-25R). IL-13 is expressed in atopic dermatitis skin lesions and plays an important role in pathogenesis of the disease. OBJECTIVE: Our aim was to determine the role of IL-25 and ILC2s in a mouse model of antigen-driven allergic skin inflammation. METHODS: Wild-type mice; mice that express an Il13-driven enhanced green fluorescent protein; and mice that lack IL-25R, IL-25 in keratinocytes, or IL-13 or IL-25R in ILC2s were subjected to acute or chronic epicutaneous sensitization with ovalbumin. Sensitized skin was examined by histology for epidermal thickening. Cellular infiltrates were analyzed for surface markers and intracellular expression of enhanced green fluorescent protein by flow cytometry. Gene expression was quantitated by RT quantitative PCR. RESULT: In both acute and chronic antigen-driven allergic skin inflammation, signaling by keratinocyte-derived IL-25 in ILC2s is important for epidermal hyperplasia, dermal infiltration by CD4+ T cells, and cutaneous expression of Il13 and the IL-13-dependent TH2-cell-attracting chemokines Cc17 and Ccl22. ILCs are the major source of IL-13 in acutely sensitized mouse skin, whereas T cells are its major source in chronically sensitized mouse skin. CONCLUSION: ILC2 activation by IL-25 is essential for IL-13 expression at sites of allergic skin inflammation.

IL-22 derived from γδ T cells restricts Staphylococcus aureus infection of mechanically injured skin.

BACKGROUND: Staphylococcus aureus is an opportunistic pathogen that colonizes the skin of patients with atopic dermatitis (AD) and aggravates their disease. Neutrophils and the cytokines IL-17A and IL-17F, which drive the expression of the neutrophil-attracting chemokines, are important for the clearance of S aureus infection. The cytokine IL-22 is often coproduced by IL-17-secreting cells. The levels of IL-22 are elevated in AD skin lesions. OBJECTIVE: We sought to determine the role of IL-22 in the clearance of S aureus infection of mouse skin subjected to tape stripping, a surrogate for scratching, a cardinal feature of AD. METHODS: S aureus was applied to the tape-stripped skin of wild-type and Il22-/- mice. Bacterial burden was evaluated by enumerating colony-forming units. Quantitative PCR and ELISA were performed to quantify Il22 mRNA and IL-22 protein in mouse and human skin. Flow cytometry was used to enumerate neutrophils in the skin. RESULTS: Scratching the skin of healthy adults and tape stripping of mouse skin induced local expression of Il22 mRNA and IL-22 protein. Induction of Il22 expression by tape stripping was dependent on IL-23 and γδ T cells. Clearance of S aureus from tape-stripped skin was significantly impaired in Il22-/- mice. Neutrophil infiltration and upregulation of expression of genes encoding the antimicrobial peptides antigen-6/urokinase-type plasminogen activator receptor related protein-1 and ß-DEFENSIN 14 and the chemokine (C-X-C motif) ligand following tape stripping were significantly impaired in Il22-/- mice. CONCLUSIONS: These findings show that IL-22 is important for limiting the growth of S aureus on mechanically injured skin and caution that IL-23 and IL-22 blockade in patients with AD may enhance susceptibility to staphylococcal skin infection.

IL-33 promotes food anaphylaxis in epicutaneously sensitized mice by targeting mast cells.

BACKGROUND: Cutaneous exposure to food allergens predisposes to food allergy, which is commonly associated with atopic dermatitis (AD). Levels of the epithelial cytokine IL-33 are increased in skin lesions and serum of patients with AD. Mast cells (MCs) play a critical role in food-induced anaphylaxis and express the IL-33 receptor ST2. The role of IL-33 in patients with MC-dependent food anaphylaxis is unknown. OBJECTIVE: We sought to determine the role and mechanism of action of IL-33 in patients with food-induced anaphylaxis in a model of IgE-dependent food anaphylaxis elicited by oral challenge of epicutaneously sensitized mice. METHODS: Wild-type, ST2-deficient, and MC-deficient KitW-sh/W-sh mice were epicutaneously sensitized with ovalbumin (OVA) and then challenged orally with OVA. Body temperature was measured by means of telemetry, Il33 mRNA by means of quantitative PCR, and IL-33, OVA-specific IgE, and mouse mast cell protease 1 by means of ELISA. Bone marrow-derived mast cell (BMMC) degranulation was assessed by using flow cytometry. RESULTS: Il33 mRNA expression was upregulated in tape-stripped mouse skin and scratched human skin. Tape stripping caused local and systemic IL-33 release in mice. ST2 deficiency, as well as ST2 blockade before oral challenge, significantly reduced the severity of oral anaphylaxis without affecting the systemic TH2 response to the allergen. Oral anaphylaxis was abrogated in KitW-sh/W-sh mice and restored by means of reconstitution with wild-type but not ST2-deficient BMMCs. IL-33 significantly enhanced IgE-mediated degranulation of BMMCs in vitro. CONCLUSION: IL-33 is released after mechanical skin injury, enhances IgE-mediated MC degranulation, and promotes oral anaphylaxis after epicutaneous sensitization by targeting MCs. IL-33 neutralization might be useful in treating food-induced anaphylaxis in patients with AD.

IL-23 induced in keratinocytes by endogenous TLR4 ligands polarizes dendritic cells to drive IL-22 responses to skin immunization.

Atopic dermatitis (AD) is a Th2-dominated inflammatory skin disease characterized by epidermal thickening. Serum levels of IL-22, a cytokine known to induce keratinocyte proliferation, are elevated in AD, and Th22 cells infiltrate AD skin lesions. We show that application of antigen to mouse skin subjected to tape stripping, a surrogate for scratching, induces an IL-22 response that drives epidermal hyperplasia and keratinocyte proliferation in a mouse model of skin inflammation that shares many features of AD. DC-derived IL-23 is known to act on CD4(+) T cells to induce IL-22 production. However, the mechanisms that drive IL-23 production by skin DCs in response to cutaneous sensitization are not well understood. We demonstrate that IL-23 released by keratinocytes in response to endogenous TLR4 ligands causes skin DCs, which selectively express IL-23R, to up-regulate their endogenous IL-23 production and drive an IL-22 response in naive CD4(+) T cells that mediates epidermal thickening. We also show that IL-23 is released in human skin after scratching and polarizes human skin DCs to drive an IL-22 response, supporting the utility of IL-23 and IL-22 blockade in AD.

Defective lymphoid organogenesis underlies the immune deficiency caused by a heterozygous S32I mutation in IκBα.

Patients with ectodermal dysplasia with immunodeficiency (ED-ID) caused by mutations in the inhibitor of NF-κB α (IκBα) are susceptible to severe recurrent infections, despite normal T and B cell numbers and intact in vitro lymphocyte function. Moreover, the outcome of hematopoietic stem cell transplantation (HSCT) in these patients is poor despite good engraftment. Mice heterozygous for the IκBα S32I mutation found in patients exhibited typical features of ED-ID. Strikingly, the mice lacked lymph nodes, Peyer's patches, splenic marginal zones, and follicular dendritic cells and failed to develop contact hypersensitivity (CHS) or form germinal centers (GCs), all features not previously recognized in patients and typical of defective noncanonical NF-κB signaling. Lymphotoxin ß receptor (LTßR)-driven induction of chemokines and adhesion molecules mediated by both canonical and noncanonical NF-κB pathways was impaired, and levels of p100 were markedly diminished in the mutant. IκBα mutant → Rag2(-/-), but not WT→IκBα mutant, bone marrow chimeras formed proper lymphoid organs and developed CHS and GCs. Defective architectural cell function explains the immunodeficiency and poor outcome of HSCT in patients with IκBα deficiency and suggests that correction of this niche is critical for reconstituting their immune function.

Cytokine profile in human eyes: contribution of a new cytokine combination for differential diagnosis between intraocular lymphoma or uveitis.

Primary intraocular lymphoma (PIOL), also called primary vitreoretinal lymphomas, often masquerades as uveitis. This misdiagnosis can result in subsequent brain involvement and oculocerebral lymphoma (OCL). In this study, we sought to characterize the helper T-cell type 1 (Th1)/Th2 cytokine profile in vitreous samples from patients with PIOL, OCL, uveitis and controls with non-inflammatory disease. Vitreous and aqueous humor samples from 87 patients with PIOL (n = 30), OCL (n = 12), uveitis (n = 34), and retinal detachment (RD) without hemorrhage (n = 11) were analyzed and their concentrations of interleukin (IL)-2, IL-4, IL-6, IL-10, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α were determined by flow cytometric bead arrays (CBA). The IL-10 levels determined by CBA were compared with those by ELISA. IL-10 concentrations measured by CBA and ELISA were highly correlated. IL-2, IL-4, and TNFα were not detected in any sample. The only cytokine detected at a significant level in samples from RD vitreous was IL-6. The IL-10/IL-6 ratio, as previously reported, was slightly higher in PIOL than in uveitis samples, but not for all patients. Cytokine profiles from PIOL and OCL samples did not differ. The combination of the IL-10/IL-6 and IL-10/IFNγ ratios was highly informative for discriminating PIOL/OCL from uveitis samples and for therapeutic follow up of PIOL. This strategy might be very helpful as an initial screening to rule out PIOL in patients thought to have uveitis.

Murine models of B-cell lymphomas: promising tools for designing cancer therapies.

Human B-cell lymphomas, the fourth most common hematologic malignancy, are currently the subject of extensive research. The limited accessibility of biopsies, the heterogeneity among patients, and the subtypes of lymphomas have necessitated the development of animal models to decipher immune escape mechanisms and design new therapies. Here, we summarize the cell lines and murine models used to study lymphomagenesis, the lymphoma microenvironment, and the efficacy of new therapies. These data allow us to understand the role of the immune system in the fight against tumors. Exploring the advantages and limitations of immunocompetent versus immunodeficient models improves our understanding of the molecular and cellular mechanisms of tumor genesis and development as well as the fundamental processes governing the interaction of tumors and their host tissues. We posit that these basic preclinical investigations will open up new and promising approaches to designing better therapies.

Influence of Tumor Location on the Composition of Immune Infiltrate and Its Impact on Patient Survival. Lessons from DCBCL and Animal Models.

Diffuse large B-cell lymphomas (DLBCLs) are heterogeneous diseases growing either in nodal or extranodal locations including the central nervous system. One key issue is to decipher the prognostic value of immune cells infiltrating these tumors as DLBCLs developing in sanctuaries are more aggressive than nodal DLCBLs. Here, we summarize available data from the literature regarding the prognostic values of the different immune cell types found in these two types of human primary tumors (i.e., nodal vs brain). In nodal DLBCLs, memory T-cells and dendritic cells (DCs) densities are of good prognostic value whereas the influence of regulatory T-cells (Tregs) is less clear, in accordance with other types of cancers. Data for primary central nervous system lymphomas are very sparse for these cell types. By contrast, CD8(+) cytotoxic T-cells seem to be of poor prognosis in either location. Their presence is linked to a loss of MHC expression providing a possible immune escape mechanism for these tumors. Clearly, tumor-associated macrophages are not associated to a significant prognostic value even in the brain where they highly infiltrate the tumor. Animal models indicate some specific features of lymphoma developing in sanctuaries by comparison to splenic location, with a higher infiltration of Tregs and less DCs, most likely reflecting the immunosuppressive context of these organs. All these informations illustrate the high impact of the immune system on patient outcome, encourage the pursuit of the immune environment's analysis and of immunotherapeutic approaches.

Th17 cells are involved in the local control of tumor progression in primary intraocular lymphoma.

BACKGROUND: Th17 cells play an important role in the pathogenesis of many autoimmune diseases, but despite some reports of their antitumor properties, too little is known about their presence and role in cancers. Specifically, knowledge is sparse about the relation of Th17 to lymphoma microenvironments and, more particularly, to the microenvironment of primary intraocular B-cell lymphoma (PIOL), an aggressive lymphoma with a poor prognosis. METHODS AND PRINCIPAL FINDINGS: In this work, we investigated the presence of Th17 cells and their related cytokines in a syngeneic model of PIOL, a subtype of non-Hodgkin lymphoma. The very small number of lymphocytes trafficking in normal eyes, which represent a low background as compared to tumor-bearing eyes, allows us to develop the present model to characterize the different lymphocyte subsets present when a tumor is developing. IL-21 mRNA was expressed concomitantly with IL-17 mRNA in tumor-bearing eyes and intracellular expression of IL-17A and IL-21 in infiltrating CD4(+) T lymphocytes. Interestingly, IL-17A production by T cells was negatively correlated with tumor burden. We also showed that IL-21 but not IL-17 inhibits tumor cell proliferation in vitro. CONCLUSIONS: These data demonstrate that IL-17A and IL-21-producing CD4(+) T cells, referred as Th17 cells, infiltrate this tumor locally and suggest that Th17-related cytokines may counteract tumor progression via IL-21 production. Thus, Th17 cells or their related cytokines could be considered to be a new therapeutic approach for non-Hodgkin B-cell lymphomas, particularly those with an ocular localization.