Identification Of Contact Allergens Research Articles

Common Contact Sensitizers among Patients with Hand Eczema: A Multicenter-Study in Nepal

Introduction: Allergic contact dermatitis in Nepal is not an uncommon disorder. Patch testing is a well established method of diagnosing allergic contact dermatitis. Patients with contact dermatitis are well known to have impaired quality of life which often leads to frequent dermatological consultations.Objective: Lack of data from Nepal has prompted us to undertake this study with the aims to know the frequency of allergic contact dermatitis and the commonest contact allergens among the patients with Hand eczema attending the out-patient department of dermatology, B.P. Koirala Institute of Health Sciences and Kathmandu Medical College Teaching Hospital.Material and Methods: A total of 256 patients were included in the study. Out of them 195 with hand eczema agreed to participate and undergo patch testing. The antigens used included the Indian standard series of patch test allergens approved by Contact and Occupational Dermatoses Forum of India.Results: Hundred and ten cases (56.4%) were patch test positive (PTP) at 48 as well as 96 hours to at least one allergen. PTP was seen more commonly in females. The most common allergen in females was nickel sulphate followed by cobalt chloride, gentamicin and mercapto mix while males were positive to potassium dichromate, followed by epoxy resin, fragrance mix and nickel sulphate.Conclusion: Patch testing has proved a useful tool for the detection of allergic contact dermatitis and for identification of contact allergens. When positive reactions correlate with environmental exposure the test usually assists the physician in establishing the cause of dermatitis, hence treating the patients and improving their quality of life.Nepal Journal of Dermatology, Venereology & Leprology, Vol.14(1) 2016, pp.14-17

Immunologie der Kontaktallergie

Contact allergy is a skin disease that is caused by the reaction of the immune system to low molecular weight chemicals. A hallmark of contact allergens is their chemical reactivity, which is not exhibited by toxic irritants. Covalent binding of contact allergens to or complex formation with proteins is essential for the activation of the immune system. As a consequence antigenic epitopes are formed, which are recognized by contact allergen-specific T cells. The generation of effector and memory T cells causes the high antigen specificity and the repeated antigen-specific skin reaction of contact allergy. New findings reveal that the less specific reaction of the innate immune system to contact allergens closely resembles the reaction to an infection. Therefore, contact allergy can be viewed as an immunologic misunderstanding since the skin contact with chemical allergens is interpreted as an infection. The growing understanding of the molecular and cellular pathologic mechanisms of contact allergy can aid the development of specific therapies and of in vitro alternatives to animal testing for the identification of contact allergens.

Activation of T-Cells from Allergic Patients and Volunteers by p-Phenylenediamine and Bandrowski's Base

Allergic contact dermatitis is commonly associated with exposure to p-phenylenediamine. The aim of this study was to determine whether p-phenylenediamine (PPD) and/or Bandrowski's base (BB) stimulate T cells from allergic patients and volunteers, and to explore the relationship between T-cell immunogenicity and allergy. Lymphocytes from allergic patients proliferated with PPD and BB (n=8). Lymphocytes from 14/16 non-allergic individuals also proliferated following stimulation, but only with BB; cord blood lymphocytes failed to respond (n=6). Glutathione, which prevented BB formation, but not binding of PPD to cells and serum, did not prevent p-phenylenediamine-specific stimulation of patient lymphocytes. T-cell clones generated from allergic patients were stimulated separately with PPD and BB, while clones from volunteers proliferated with BB alone. Patient and volunteer clones secreted IL-4, IL-5, IL-13, TNF-alpha, MIP-1alpha, MIP-1beta, and RANTES. These data show that activation of T lymphocytes from allergic individuals alone with PPD represents an important discrimination between allergic and non-allergic groups. BB-specific T cells are found in both allergic patients and volunteers, but not in cord blood. Their presence seems to reflect an acquired immune response, which is not translated into an allergic reaction.

Microarray-Based In Vitro Test System for the Discrimination of Contact Allergens and Irritants: Identification of Potential Marker Genes

Animal tests have been used to characterize the potential of chemicals to produce allergic contact dermatitis, but this approach is increasingly a matter of public and political concern. Our aim was to develop and validate an alternative in vitro test that can identify contact allergens. We developed a targeted microarray containing oligonucleotide probes for 66 immune-relevant genes and analyzed gene expression in monocyte-derived dendritic cells (Mo-DCs) treated with 1 irritant (SDS) and 2 prominent contact allergens, nickel and Bandrowski's base (BB), which is the oxidation product of the most important hair dye allergen, p-phenylenediamine. Comparing RNA amounts in chemical-treated and solvent-treated cells, we identified significant changes in the expression of 21 genes and 10 genes after exposure of immature DCs (iDCs) to nickel and BB, respectively, but not after exposure to SDS. Eight genes were differentially expressed after application of both nickel and BB. Real-time PCR was used to confirm the results for selected genes. We propose a microarray-based in vitro test that might allow the identification of contact allergens. Independently from donor variability, several immune-relevant genes were up- or downregulated after the application of the tested sensitizers to iDCs, therefore presenting potential marker genes. While reducing the number of laboratory animals used, this test would also enable reliable analysis of chemicals using a human system.

High-performance liquid chromatography of unmodified rosin and its applications in contact dermatology

Rosin is a well recognised skin sensitiser and is also amongst the most common causes of occupational asthma. Due to its complex chemical composition, it is difficult to isolate its many components and this has hindered progress in the identification of the specific respiratory and contact allergens it contains. This paper reports the application of high-performance liquid chromatography and other analytical techniques to the isolation and identification of contact allergens in complex mixtures such as rosin. HPLC methods were developed in order to isolate as many rosin components as possible and these were then patch tested on rosin sensitive individuals. The structure of the most dermatologically active component was then determined using mass spectrometry, nuclear magnetic resonance and infrared techniques. An HPLC method has also been developed which will enable the identification of rosin in commercial products, providing a valuable tool for determining the cause of rosin contact allergy. Furthermore, mass spectral data for the common abieitic-type resin acids are compiled which were used to confirm the identification of the HPLC resin acid peaks and have not been reported previously.

Identification of contact allergens in unmodified rosin using a combination of patch testing and analytical chemistry techniques.

In order to investigate the contact allergens in the unmodified colophony (rosin) used in routine patch testing, preparative chromatographic techniques were used to separate its components which were then patch tested on colophony-sensitive individuals. The chemical structure of the dermatologically active components was elucidated using mass spectrometry, nuclear magnetic resonance and infra-red techniques. The study shows that oxidized resin acids are stronger sensitizers than the resin acids themselves, the most potent contact allergen being 7-oxydehydroabietic acid (purity 92%). At naturally occurring concentrations (relative to abietic acid) all unoxidized resin acids were found to play an insignificant part, individually, in colophony dermatitis, except abietic acid (purity 99%), which was found to be a weak but important allergen. The commercial Trolab abietic acid preparation (unknown purity) was found to be dermatologically more active than purified abietic acid.

The Role of Structure-activity Relationships and Expert Systems in Alternative Strategies for the Determination of Skin Sensitisation, Skin Corrosivity and Eye Irritation

A historical database containing the results of 294 defined single substances tested in the guinea-pig maximisation test, carried out according to a single protocol, was used to derive a set of structural alerts for skin sensitisation, which have been incorporated into the expert system, DEREK. Together with an assessment of percutaneous absorption, this system forms an integral part of a strategic approach to the identification of contact allergens. Quantitative structure-activity relationships (QSARs) were derived for the skin corrosivity of organic acids and bases, and for the eye irritation potential of neutral organic chemicals. The independent variables used for these analyses were selected on the basis of the putative mechanisms for skin irritation or corrosivity and for eye irritation, respectively. Data sets were analysed using principal components analysis; plots of the first two principal components for each data set showed that the analyses were able to discriminate well between chemicals with different classifications of toxicological activity. The derived QSARs are expected to give useful predictions of skin corrosivity and eye irritancy for new or untested chemicals in these classes. Although the development of these techniques is still at a very early stage, they are already able to play an important part in proposed strategies for the reduction of experimental animal usage. In the long term, it should be possible to conduct safety evaluations using fewer experimental animals or no animals at all. However, acceptance by regulatory authorities will be a key factor in realising the full benefits of the approach.

Identification of contact allergens in C.I. Solvent Red 23 (commercial Sudan III) by chemical analysis and animal testing

C.I. Solvent Red 23, commercial Sudan III, is widely used in cosmetic products. Chemical analyses and guinea pig sensitization tests were carried out to identify its contact allergens. In the Magnusson & Kligman guinea pig maximization test, C.I. Solvent Red 23 showed 20% positive reactions. By conducting chemical analyses with HPLC and GLC, 2-naphthol (82 ppm), azobenzene (48 ppm), Sudan I (570 ppm) and many unknown impurities, as well as the main constituent pigment Sudan III (87%), were found. The chemical structure of one unknown impurity was identified as an isomer of Sudan III. We found that purified Sudan III showed no positive reaction, while the isomer elicited 30% positive reactions, in the same guinea pig test. Furthermore, cross-sensitization with p-phenylenediamine was investigated using the guinea pig test. Animals sensitized with p-phenylenediamine also showed positive elicitation reactions with purified Sudan III. From these results, the contact allergenicity of C.I. Solvent Red 23 is considered to be due to impurities, including the isomer of Sudan III, 1-(o-phenylazophenylazo)-2-naphthol. Positive reactions to Sudan III previously demonstrated in hairdressers are due to cross-sensitivity with p-phenylenediamine.

Identification of contact allergens in Solvent Red 23, commercial Sudan III, by chemical analysis and animal testing

Identification of contact allergens in Solvent Red 23, commercial Sudan III, by chemical analysis and animal testing

Identification of contact allergens using the murine local lymph node assay: Comparisons with the buehler occluded patch test in guinea pigs

A murine local lymph node assay has been developed for the identification of contact sensitizing chemicals. In the present study, the performance of the local lymph node assay has been evaluated with twenty-four coded chemicals of previously unknown skin sensitizing potential and the results compared with predictions made from concurrent occluded patch tests (Buehler tests) in guinea pigs. The data presented demonstrate that the local lymph node assay successfully identified those chemicals that were classified as moderate or strong skin sensitizers in the Buehler test. In the present series of experiments, chemicals predicted to be mild sensitizers in the Buehler test were classified as 'not strong sensitizers' in the local lymph node assay. In the majority of instances, the Buehler test and local lymph node assay were in agreement with regard to the identification of non-sensitizing chemicals. However, two chemicals that were classified as non-sensitizers in the guinea pig test exhibited positive responses in the local lymph node assay and were predicted to be sensitizers. Some coloured chemicals resulted in obscured Buehler readings and, here, assessment was based upon histological examination of the challenge site. These compounds were examined also in the local lymph node assay and similar predictions of sensitizing potential were made. Taken together, the data reveal close, but not absolute, concordance between the local lymph node assay and the Buehler test. The relative merits of these predictive test methods are discussed.

The Identification of Contact Allergens by Human Assay III. The Maximization Test: A Procedure for Screening and Rating Contact Sensitizers

The Identification of Contact Allergens by Human Assay III. The Maximization Test: A Procedure for Screening and Rating Contact Sensitizers

Allergic contact dermatitis in the hamster and in other rodents.

The first, and for a long time the only, experimental animal for the study of allergic contact dermatitis (ACD) was the guinea pig (1). Thus the basic studies that related sensitization potential to the ability of a low molecular weight allergen to couple to protein, that established the requirement for viable lymphoid cells (not sera) for the passive transfer of hypersensitivity to simple chemical allergens, and that demonstrated the induction of a specific immunological unresponsiveness to contact allergens, were done in the guinea pig (2,3, 4,5). Indeed, the guinea pig still remains the animal of choice for the identification of contact allergens of man (6,7). In 1968, the technique of measuring increased ear thickness as a way of assessing induced inflammation by contact allergens in the mouse was introduced (8); in contrast to the guinea pig, inflammatory skin reactions on the flank of the mouse are difficult to evaluate since these reactions lack both erythema and easily defined induration. The ear thickness technique recently has been extended to studies of allergic contact dermatitis in the hamster (9,10) and we are using the same methodology to evaluate ACD hypersensitivity in rats (11). This report examines ACD in the hamster and relates it to ACD in other species.

The Identification of Contact Allergens by Animal Assay. The Guinea Pig Maximazation Test

The Identification of Contact Allergens by Animal Assay. The Guinea Pig Maximazation Test

The Identification of Contact Allergens by Human Assay: II. Factors Influencing the Induction and Measurement of Allergic Contact Dermatitis

The Identification of Contact Allergens by Human Assay: II. Factors Influencing the Induction and Measurement of Allergic Contact Dermatitis

The Identification of Contact Allergens by Human Assay: I. A Critique of Standard Methods

The Identification of Contact Allergens by Human Assay: I. A Critique of Standard Methods

The Identification of Contact Allergens by Human Assay: III. The Maximization Test: A Procedure for Screening and Rating Contact Sensitizers

The Identification of Contact Allergens by Human Assay: III. The Maximization Test: A Procedure for Screening and Rating Contact Sensitizers