F. Bérard

Detection and quantification of drug-specific T cells in penicillin allergy

Drug allergic reactions presenting as maculo‐papular exanthema (MPE) are mediated by drug‐specific T cells. In this study, the frequency of circulating specific T cells was analyzed by interferon‐γ (IFN‐γ) enzyme‐linked immunospot assay in 22 patients with an allergic MPE to amoxicillin (amox). Amox‐specific circulating T cells were detected in 20/22 patients with frequencies ranging from 1 : 8000 to 1 : 30 000 circulating leucocytes. No reactivity was observed in 46 control patients, including 15 patients with immunoglobulin E‐mediated allergy to amoxicillin, 11 patients with a history of drug‐induced MPE but tolerant to amoxicillin and 20 healthy individuals. Furthermore, amox‐specific T cells were still detectable several years after the occurrence of the allergic reaction even after strict drug avoidance. Finally, analysis of drug‐specific T cells in one patient allergic to ticarcillin (a penicillin antibiotic distinct from amox) revealed the presence of IFN‐γ‐producing T cells reactive to ticarcillin and several other betalactam antibiotics, suggesting that the IFN‐γ ELISPOT assay is able to detect T cell cross‐reactivity against chemically related drugs. These findings confirm that drug‐induced MPE is associated with the presence of specific T cells in blood and further suggest that the IFN‐γ ELISPOT is a sensitive assay which could improve the diagnosis of betalactam allergy.

Psychological Stress Exerts an Adjuvant Effect on Skin Dendritic Cell Functions In Vivo

Psychological stress affects the pathophysiology of infectious, inflammatory, and autoimmune diseases. However, the mechanisms by which stress could modulate immune responses in vivo are poorly understood. In this study, we report that application of a psychological stress before immunization exerts an adjuvant effect on dendritic cell (DC), resulting in increased primary and memory Ag-specific T cell immune responses. Acute stress dramatically enhanced the skin delayed-type hypersensitivity reaction to haptens, which is mediated by CD8+ CTLs. This effect was due to increased migration of skin DCs, resulting in augmented CD8+ T cell priming in draining lymph nodes and enhanced recruitment of CD8+ T cell effectors in the skin upon challenge. This adjuvant effect of stress was mediated by norepinephrine (NE), but not corticosteroids, as demonstrated by normalization of the skin delayed-type hypersensitivity reaction and DC migratory properties following selective depletion of NE. These results suggest that release of NE by sympathetic nerve termini during a psychological stress exerts an adjuvant effect on DC by promoting enhanced migration to lymph nodes, resulting in increased Ag-specific T cell responses. Our findings may open new ways in the treatment of inflammatory diseases, e.g., psoriasis, allergic contact dermatitis, and atopic dermatitis.

Pathophysiology of urticaria.

Urticaria is dermal edema resulting from vascular dilatation and leakage of fluid into the skin in response to molecules released from mast cells. The major preformed mediator histamine produces a prototypic, short-lived urticaria. However, the clinical spectrum and pattern of lesions indicate that other molecules, including prostaglandins, leukotrienes, cytokines, and chemokines, produced at different times after mast cell activation contribute to the polymorphism of this symptom and the variable evolution of this disease. It is a common practice to distinguish immunological and nonimmunological urticaria. Immunological urticaria is a hypersensitivity reaction mediated by antibodies and/or T-cells that results in mast cell activation. Although immunoglobulin (Ig)E-mediated type I hypersensitivity (HS) was long postulated to be the major immunological pathway associated with mast cell activation, interaction between IgE-bound mast cells and allergens is unlikely to be the mechanism by which urticaria develops in most patients. It is now well established that urticaria may result from the binding of IgG auto-antibodies to IgE and/or to the receptor for IgE molecules on mast cells, thus corresponding to a type II HS reaction. These auto-immune urticarias represent up to 50% of patients with chronic urticaria. Mast cell activation can also result from type III HS through the binding of circulating immune complexes to mast cell-expressing Fc receptors for IgG and IgM. Finally, under certain circumstances, T-cells can induce activation of mast cells, as well as histamine release (type IV HS). Nonimmunological urticarias result from mast cell activation through membrane receptors involved in innate immunity (e.g., complement, Toll-like, cytokine/chemokine, opioid) or by direct toxicity of xenobiotics (haptens, drugs). In conclusion, urticaria may result from different pathophysiological mechanisms that explain the great heterogeneity of clinical symptoms and the variable responses to treatment.

Skin-infiltrating CD8+ T cells initiate atopic dermatitis lesions

Skin lesions in the allergic form of atopic dermatitis (AD) are induced by allergen-specific T cells that infiltrate the skin at the site of allergen exposure. Although Th2-type CD4+ T cells appear to be crucial in AD pathophysiology, little is known about the contribution of CD8+ T cells in the development of the allergic skin inflammation. In the present study, we have analyzed the respective role of CD8+ and CD4+ T cells in the development of AD skin lesions in a mouse model of allergen-induced AD. In sensitized mice, CD8+ T cells are rapidly and transiently recruited to the allergen-exposed site and initiate the inflammatory process leading to skin infiltration with eosinophils and Th1/Th2-producing cells. CD8+ T cell-depleted mice show no inflammation, demonstrating that these cells are mandatory for the development of AD. In contrast, CD4+ T cell-depleted mice develop a severe form of eczema. Furthermore, adoptive transfer of CD8+ T cells from sensitized mice into naive recipient mice leads to skin inflammation soon after allergen exposure. These data indicate that allergen-primed CD8+ T cells are required for the development of AD-like lesions in mice.

Negativity of the basophil activation test in quinolone hypersensitivity: a breakthrough for provocation test decision-making.

Background: Quinolone hypersensitivity reactions are being more frequently reported. Skin tests in investigations of patients are known to not be fully reliable. The provocation test thus remains the gold standard in the definitive diagnosis of allergy, despite the risks involved. The aim of this study was to evaluate basophil activation tests (BATs) in the diagnosis of immediate-type reactions to quinolones. Methods: Thirty-four patients who presented an immediate-type hypersensivity reaction less than an hour after quinolone administration were studied. The allergologic workup of these patients consisted of a careful clinical history, a skin test and a BAT with the culprit quinolone. If not contraindicated, and in the case of high probability of a nonallergic reaction, provocation tests were performed to assess the nonimmunologic nature of the hypersensitivity. Results: Among the 34 patients studied, 17 (50%) presented a negative BAT to the suspected quinolone, while the other 17 (50%) patients presented a positive BAT for quinolone at the time of their reaction. Among the 17 patients with negative BATs, 15 (2 of whom had had positive skin tests) had quinolone successfully reintroduced. Conclusions: Our report suggests that the BAT, if negative for the culprit quinolone, is a valuable tool in the decision whether or not to perform provocation tests in patients with a history of immediate-type reaction to quinolones, in order to exclude an allergic reaction.

Esomeprazole-induced DRESS syndrome. Studies of cross-reactivity among proton-pump inhibitor drugs

intervals of 1, 2 and 4 weeks between the sessions. The persistence of negative results of intradermal testing was confirmed before each desensitization procedure. Loss of skin sensitivity appeared to be a good predictor of tolerance of the drug. Both patients continued receiving cyanocobalamin injections monthly with good tolerance. Drug desensitization is time dependant and re-sensitization recurs after awhile.We have little information about the length of time the drug tolerance persists. It is thought to be in the range of weeks. According to our experience, with the above patients, it persists for at least 4 weeks. We did not asses a longer time interval and therefore would advise four weekly treatmentwith the therapeuticdose. Our patients showed cross sensitivity between cyanocobalamin and hydroxicobalamin therefore we had no substitute drug available. Cross sensitivity has previously been described although it is not always found (2, 3). In a patient with hydroxicobalamin allergy and a negative result to cutaneous testing with cyanocobalamin, this latter preparation may be tolerated. We have not been able to measure specific IgE in patients serum, though the mechanism is likely to be IgE dependant. We suspect this to be true as both sensitizations occurred after a period of tolerance with increasing severity of the reaction after each injection. We were able to confirm positive skin test results in our patients as compared with negative test results in control subjects. The preparation of cyanocobalamin we used did not contain benzyl alcohol preservative which has been involved in patient reacting to vitamin B12 injection (4). The allergen involved in vitamin B12 reactions is likely to be a hapten. We are indebted to Lucy Riddington, allergy specialist nurse, for technical support.

Chronic spontaneous urticaria is not an allergic disease

The links between chronic urticaria, IgE sensitization and allergy have been much discussed but little studied. We investigated IgE sensitization and allergy in 128 adult chronic urticaria patients during 2006-2008. During a one-day hospitalisation, the patients answered a standardized questionnaire and underwent blood serum analysis, physical tests and skin prick-tests. IgE sensitization to environmental allergens was defined by the positivity of at least one skin prick test and/or elevated levels of serum IgE ≥ 300 Kui/L. The chronic urticaria was considered allergic if: i) a high correlation between positive skin prick tests to a clinically relevant allergen and the case history was found; ii) complete remission of urticaria occurred within two months of allergen withdrawal. Of 105 patients with interpretable skin prick tests, 46.7% were IgE sensitized. Two patients had clinically relevant positive skin prick tests but their chronic urticaria had many other triggering factors and neither was in complete remission after withdrawal of these allergens. IgE sensitization is higher in chronic urticaria patients than in the global adult population, suggesting that it is one important etiopathogenic factor in chronic urticaria. However, it cannot be considered as the expression of an IgE-mediated allergy but as a chronic inflammatory disease, more frequent in IgE sensitized people and favoured by multiple factors, among which IgE-mediated allergy is exceptional.

Patch testing in atopic dermatitis patients.

The exposure of atopic dermatitis (AD) patients to aeroallergens or food allergens can exacerbate or maintain the disease. Atopy patch tests (APTs) are able to identify these triggering factors and consist of the epicutaneous application of allergens for 48 hours, with an evaluation of the eczematous lesions induced after 48 and 72 hours, according to the reading criteria of the European Task Force on Atopic Dermatitis (ETFAD). APTs show a higher specificity than skin prick and specific IgE tests, since the pathophysiological mechanism of the reaction induced is very similar to that which occurs in AD lesions. The standardization of APTs to aeroallergens has brought a certain reliability to this method, which is not the case for food APTs, in which the positive predictive value must be improved to avoid any unnecessary dietary restrictions. Thus, optimization of APTs and progress in the knowledge of the pathophysiology of eczemas could help to develop new immunobiological diagnostic methods and specific immunotherapy for AD.

CD8+ T cells mediate skin allergy to amoxicillin in a mouse model

To cite this article: Rozieres A, Vocanson M, Rodet K, Benetiere J, Bienvenu J, Berard F, Hennino A, Nicolas J‐F. CD8+ T cells mediate skin allergy to amoxicillin in a mouse model. Allergy 2010; 65: 996–1003.

Cytoplasmic accumulation of peanut agglutinin-binding glycoconjugates in the cells of primary melanoma correlates with clinical outcome

In an experimental model, human melanoma cell lines enriched for cells that express the glycoconjugate B-D galactose N-acetyl-D-galactosamine, which reacts with the peanut agglutinin lectin (PNA), are associated with an increase in the frequency of metastases. We previously showed that this glycoconjugate is expressed on the cells of some primary melanomas in humans and that such cells are found selectively in melanomas with a high risk for developing metastases and causing death. Using fixed archival tissues from 99 primary melanomas and lectin histochemistry, we found 65 tumors that contained melanoma cells that were PNA-positive. PNA-reactive cells were not identified in normal melanocytes or in the nevocytes of 24 nevi. PNA-reactive material accumulates adjacent to the nucleus in the area of the Golgi apparatus, initially as a tiny dot, but later in quantities sufficient to displace and indent the nucleus, producing a signet ring cell-like appearance. Tumor cells containing PNA-reactive material were associated with more evolved, deeper, and thicker tumors. Two melanomas up to Clark level II were PNA positive (20%), compared with 60% of level III, 76% of level IV, and 100% of level V. Five of 13 tumors less than 0.76 mm thick (39%) were positive, compared with 50% of tumors 0.76 to 1.49 mm thick, 64% of tumors 1.5 to 2.99 mm thick, and 85% of tumors 3 mm thick or thicker. PNA-reactivity was negatively correlated with disease-free survival (PNA-negative, 49.2+/-23 months; PNA-positive grade 1, 41.6+/-26 months and PNA-positive grade 2, 24.4+/-23 months), survival rate 5 years after initial treatment (PNA-negative, 84.8%; PNA-positive grade 1, 63.8%; and PNA-positive grade 2, 31.3%) and disease-free survival at 5 years after initial treatment (PNA-negative, 69.7%; PNA-positive grade 1, 53.2%; and PNA-positive grade 2, 25%).