Invariant NKT Cells Suppress CD8+ T-Cell–Mediated Allergic Contact Dermatitis Independently of Regulatory CD4+ T Cells

Invariant natural killer T (iNKT) cells expressing a CD1d-restricted invariant αβTCR have key regulatory roles in autoimmunity, pathogen immunity, and tumor surveillance, but their function in the control of allergic skin diseases remains poorly documented. Using a model of contact hypersensitivity (CHS) to the hapten DNFB, we show here that iNKT cell deficiency results in enhanced skin inflammation due to augmented hapten-specific IFN-γ-producing CD8+ effectors in skin draining lymph nodes (dLNs) and their massive recruitment into the allergen-exposed skin. Adoptive transfer and antibody depletion experiments as well as in vitro studies revealed that iNKT cells (1) reduce the severity of CHS, even in presensitized mice, (2) require hapten presentation by CD1d+ dendritic cells (DCs) to dampen skin inflammation, and (3) produce IL-4 and IL-13 after CD1d-dependent in vitro stimulation by hapten-loaded DCs only in the presence of IFN-γ released from activated CD8+ effector T cells. In corollary, mice double deficient in IL-4 and IL-13 exhibit an exacerbated CHS. Finally, iNKT-suppressive function is independent of Foxp3+ regulatory T cells (Tregs). These data highlight that, besides Foxp3+ Tregs, iNKT cells are potent downregulators of CD8+ T cell–mediated CHS, and underscore that both cell types are important for the regulation of allergic skin inflammation

Eczéma allergique de contact : Comment ré-induire une tolérance ?

L’eczéma allergique de contact est une dermatose inflammatoire fréquente, due à l’activation de lymphocytes T (LT) CD8+ cytotoxiques spécifiques d’haptènes en contact avec la peau. Les LT CD4+ sont, quant à eux, doués d’une fonction régulatrice et tolérogène, puisqu’ils limitent l’inflammation cutanée chez les patients (régulation) et préviennent le développement des LT effecteurs chez les individus sains (tolérance) : l’eczéma correspond donc à une rupture de la tolérance immunitaire aux haptènes présents dans l’environnement quotidien. Plusieurs sous-populations de LT CD4+ régulateurs (LT reg), parmi lesquelles celle des LT CD4+CD25+ naturels, sont impliquées dans la tolérance et la régulation de l’eczéma, via la production des cytokines immunosuppressives IL-10 (interleukine-10) et TGFβ (transforming growth factor β). Les travaux en cours ont pour objectif de ré-induire une tolérance immunitaire dans l’eczéma, soit en améliorant les méthodes existantes d’induction de tolérance aux haptènes (tolérance orale, tolérance à faibles doses, immunothérapie spécifique, tolérance induite par les rayons ultraviolets), soit en développant de nouvelles molécules capables d’activer les LT reg. Plus généralement, les données issues de ces travaux devraient pouvoir être appliquées au traitement des maladies auto-immunes ou allergiques, caractérisées par un déficit fonctionnel ou quantitatif en Ltreg à l’origine d’une rupture de la tolérance aux auto-antigènes ou aux allergènes de l’environnement.Allergic contact dermatitis (ACD) is a skin inflammatory disease mediated by activation of CD8+ cytotoxic T cells specific for haptens in contact with the skin. CD4+ T cells behave as both regulatory and tolerogenic cells since they down-regulate the skin inflammation in patients with ACD (regulation) and prevent the developement of eczema (tolerance) in normal individuals. Thus, ACD corresponds to a breakdown of immune tolerance to haptens in contact with the skin. Several regulatory CD4+ T cell subsets (Treg), especially CD4+CD25+ natural Treg cells, are involved in immunological tolerance and regulation to haptens through the production of the immunosuppressive cytokines IL-10 and TGF-β. Ongoing strategies to re-induce immune tolerance to haptens in patients with eczema include improvement of existing methods of tolerance induction (oral tolerance, low dose tolerance, allergen-specific immunotherapy, UV-induced tolerance) as well as development of new drugs able to activate IL-10 producing Treg cells in vivo. Ongoing and future progress in this area will open up new avenues for treatment of eczema and more generally autoimmune and allergic diseases resulting from a breakdown of tolerance to autoantigens and allergens, respectively

Activation of Flucloxacillin-Specific CD8+ T-Cells With the Potential to Promote Hepatocyte Cytotoxicity in a Mouse Model

There are currently no animal models of drug-induced liver injury (DILI) where the adaptive immune system has been shown to damage the liver. Thus, it is difficult to explore the mechanistic basis of the tissue injury. The aim of this study was to use C57BL/6 CD4+-deficient mice with a mutation in the αβ gene encoding for Major histocompatibilty complex (MHC) class II molecules to (1) develop a mouse model of flucloxacillin sensitization, (2) explore whether drug-specific CD8+ kill primary hepatocytes, and (3) analyze perturbations in liver integrity following oral exposure to flucloxacillin. CD8+ T-cells from lymph nodes of flucloxacillin-sensitized mice were stimulated to proliferate, secrete interferon (IFN-γ) and granzyme B, and induce hepatocyte apoptosis in a concentration-dependent manner following ex vivo stimulation. The T-cell response was antigen-specific; T-cells were not activated with other β-lactam antibiotics. Furthermore, T-cell responses only occurred in the presence of flucloxacillin-pulsed antigen presenting cells. In separate experiments, flucloxacillin-specific T-cells were induced to migrate to the mesenteric lymph nodes using retinoic acid, prior to administration of oral flucloxacillin, and analysis of plasma biomarkers of liver injury. Oral exposure to flucloxacillin resulted in mild elevations in alanine aminotransferase, liver, and gall bladder leukocyte infiltration and a marked swelling of the gall bladder. Thus, CD4+-deficient mice represent a promising model to study the role of the adaptive immune system in DIL

T-cell recognition of chemicals, protein allergens and drugs: towards the development of in vitro assays

Chemicals can elicit T-cell-mediated diseases such as allergic contact dermatitis and adverse drug reactions. Therefore, testing of chemicals, drugs and protein allergens for hazard identification and risk assessment is essential in regulatory toxicology. The seventh amendment of the EU Cosmetics Directive now prohibits the testing of cosmetic ingredients in mice, guinea pigs and other animal species to assess their sensitizing potential. In addition, the EU Chemicals Directive REACh requires the retesting of more than 30,000 chemicals for different toxicological endpoints, including sensitization, requiring vast numbers of animals. Therefore, alternative methods are urgently needed to eventually replace animal testing. Here, we summarize the outcome of an expert meeting in Rome on 7 November 2009 on the development of T-cell-based in vitro assays as tools in immunotoxicology to identify hazardous chemicals and drugs. In addition, we provide an overview of the development of the field over the last two decades

Hot homogenization process optimization for fragrance encapsulation in solid lipid nanoparticles: Fragrance encapsulation in SLN by hot homogenization process

International audienceSolid lipid nanoparticles (SLNs) loaded with perfume were prepared using a hot homogenization process coupled with ultrasounds. The objective was to develop a simple process adjustable to several kinds of lipids. The process comprised two steps: a pre‐emulsion of the melted lipids in water followed by a size reduction by sonication, before cooling. The study of several formulation parameters showed that the size distribution of SLNs depended essentially on the sonication step, and especially on the ultrasounds power and time. Five types of SLNs loaded with perfume were produced, based on petrolatum, candelilla, shea butter, C10‐18 triglycerides, and cetyl palmitate. The size distribution was below 200 nm with a narrow size distribution. Moreover, high encapsulation efficiency was obtained, at least 66.5% (±0.5) for petrolatum SLNs and 94.9% (±0.5) for cetyl palmitate SLNs and the loading % was comprised between 4.9% (±0.5) (petrolatum) and 7.0% (±0.5) (cetyl palmitate). A correlation between the partition coefficient of the molecules and the encapsulation efficiency was established for all lipids except cetyl palmitate. Cetyl palmitate, candelilla and petrolatum SLNs were stable for at least one month at 4 °C and 25 °C

When Joints Fail: Identifying the Allergen Helps

More than 1 million joint replacement surgeries are performed each year in the United States, and failure occurs in 10% of them, raising major health and economic burdens. The reasons for failure are multiple and include malposition, infection, and hypersensitivity (HS)/allergy to implant components. The term "hypersensitivity", defining an inflammatory reaction to the implant components, is more appropriate than the term "allergy," because the implant-induced inflammation can be mediated by innate or adaptive immunity. Implant HS, also sometimes called "adverse reaction to metal debris" or "pseudotumor- like periprosthetic tissue reactions" in the specific condition or metal-on-metal hip replacement, undoubtedly exists, but it cannot be stated to always be an allergic reaction. Innate HS, also referred to as nonallergic HS, may develop in response to the generation of metal/polymer wear debris, which causes local inflammation due to activation of macrophages, thus leading to osteoclast triggering, bone resorption, and implant loosening. There is no diagnostic test for nonallergic HS. Conversely, adaptive HS, that is, allergy to prosthesis, also called type IV HS, is mediated by specific T cells that infiltrate the periimplant tissue where they are activated by antigen-presenting cells. The main allergens are metals (nickel, chromium, cobalt) and bone cement compounds. T-cell activation leads to the recruitment of leucocytes, which will cause joint inflammation, pain, and loosening

Encapsulation of Fragrance Mixture I Into Poly-<I>ε-</I>Caprolactone Nanoparticles by Nanoprecipitation Process

International audienc

Eugenol Loaded Solid Lipid Nanoparticles: A Comparative Study of Two Processes

International audienc

Topical Ivermectin 10~mg/g and Oral Doxycycline 40~mg Modified-Release: Current Evidence on the Complementary Use of Anti-Inflammatory Rosacea Treatments

International audienceRosacea is a common, chronic inflammatory skin disease that can present with a variety of signs and symptoms. The potentially simultaneous occurrence of different signs and symptoms is due to different underlying inflammatory pathways, emphasizing the need for complementary treatment approaches. Topical ivermectin cream (10~mg/g) and systemic, oral anti-inflammatory doxycycline (40 mg modified-release) are both approved for the treatment of papulopustular rosacea (PPR). Whether or not a combined therapeutic approach may be more beneficial than monotherapy for patients with PPR remains to be tested. Here, we summarize underlying inflammatory pathways implicated in rosacea and clarify the impact of these two agents on selective pathways during inflammation, due to specific characteristics of their individual mechanisms of action (MoA). Based on the complementary MoA of doxycycline modified-release and ivermectin, a scientific rationale for a combined therapy targeting inflammatory lesions in rosacea is given. We propose that topical ivermectin cream is a promising new candidate as first-line treatment to target the inflammatory lesions of rosacea, which can be used in combination with systemic doxycycline modified-release to provide an optimal treatment approach considering all inflammatory pathways involved in PPR. Funding Galderma