Delayed-type hypersensitivity reaction to paraphenylenediamine is mediated by 2 different pathways of antigen recognition by specific αβ human T-cell clones

Background: Allergic contact dermatitis to paraphenylenediamine (PPD) is a frequent cause of morbidity and occupational disability. Objective: The aim of the study was to characterize T-cell responses to PPD and Bandrowski's base (BB), an autoxidation product of PPD, by using polyclonal and monoclonal T-lymphocyte cultures. Methods: PPD- and BB-driven proliferation of PBMCs and T-cell clones (TCCs) was assessed by means of tritiated thymidine incorporation. Surface markers were studied by means of flow cytometry, and cytokine generation was assessed with an ELISA. Results: TCCs, with one exception, were CD4⁺/CD45RO⁺, and T-cell receptors were αβ⁺. Three of 6 TCCs expressed Vβ 16. TCC stimulation was HLA-DP restricted, and TCCs secreted IL-4, IL-5, and marginal levels of IFN-γ. TCCs reacted to both PPD and BB. Presentation of BB to TCCs was dependent on viable antigen-presenting cells (APCs) pulsed for 4 hours, and fixed APCs failed to stimulate TCCs. Moreover, polyclonal responses to BB were enhanced by metabolically active enzymes, such as cytochrome P450 enzymes. BB has to be metabolized and processed. In contrast, fixation of APCs did not impair their ability to present PPD to TCC, whereas pulsing of APCs with PPD failed to stimulate TCCs. Thus PPD had to be present during the process, and polyclonal stimulation was not enhanced by cytochromes. Conclusion: These results suggest that PPD itself can be recognized by T cells through a processing-independent pathway, whereas its autoxidation product, BB, required processing and possibly metabolism to stimulate the same TCC. Our data demonstrate that 2 distinct pathways of antigen presentation to activate specific TCCs are involved in the immune response to PPD. (J Allergy Clin Immunol 2002;109:1005-11.)     

The basophil activation test in wasp venom allergy: sensitivity, specificity and monitoring specific immunotherapy

BACKGROUND: As in vitro diagnosis of wasp venom sensitization by specific serum IgE has a sensitivity of only 60-80%, additional in vitro tests are desirable. Basophil activation is associated with the expression of CD63 and its measurement has been proposed as a novel in vitro test for immediate-type allergy. Furthermore, to date, no in vitro test exists to monitor successful specific immunotherapy (SIT) with wasp venom. Therefore, the potentially harmful sting challenge is still recommended. OBJECTIVE: We compared the CD63-based basophil activation test (BAT) in the diagnosis of wasp venom allergy with skin tests and measurement of specific IgE. Furthermore, we investigated whether BAT can predict the outcome of the sting challenge in patients on SIT. METHODS: Fifty patients with a systemic reaction caused by a wasp sting and 20 controls were studied. Intracutaneous tests were performed with wasp and bee venom in the suspected allergics. Specific IgE was determined by the CAP-FEIA method and basophil activation by flow cytometry upon double staining with anti-IgE/anti-CD63 mAb. Twenty-five patients were sting challenged 6 months after starting SIT and the BAT was repeated before challenge. RESULTS: Sensitivity of the intracutaneous tests, specific IgE and BAT was 100, 76, and 92%, respectively. Specificity of specific IgE and the BAT was 85 and 80%, respectively. The cut-off for a positive BAT was 15% CD63+ basophils. There was a positive correlation between IgE reactivity to wasp venom and the number of CD63+ basophils (r = 0.65). Although no patient had a systemic reaction upon sting challenge, in most subjects basophil activation did not decrease when compared with the BAT before SIT. CONCLUSIONS: Quantitation of basophil activation by CD63 expression is a valuable new in vitro method for diagnosis of allergy to hymenopteran venoms. The CD63-based BAT is a helpful tool for the complementation of routine diagnostic tests such as specific IgE as it increases sensitivity of in vitro detection of sensitization. However, this in vitro method does not offer an alternative to the sting challenge in monitoring successful SIT.     

Para-phenylenediamine and allergic sensitization: risk modification by N-acetyltransferase 1 and 2 genotypes

Background  Para -phenylenediamine (PPD) is a common contact sensitizer causing allergic contact dermatitis, a major skin problem. As PPD may need activation to become immunogenic, the balance between activation and/or detoxification processes may influence an individual's susceptibility. PPD is acetylated and the metabolites do not activate dendritic-like cells and T cells of PPD-sensitized individuals.
Objectives  To investigate whether PPD can be acetylated in vitro by the two N -acetyltransferases 1 (NAT1) and 2 (NAT2). Based on the assumption that N -acetylation by NAT1 or NAT2 is a detoxification reaction with respect to sensitization, we examined whether NAT1 and NAT2 genotypes are different between PPD-sensitized individuals and matched controls.
Methods  Genotyping for NAT1 and NAT2 polymorphisms was performed in 147 PPD-sensitized individuals and 200 age- and gender-matched controls.
Results  Both PPD and monoacetyl-PPD were N -acetylated in vitro by recombinant human NAT1 and to a lesser extent by NAT2. Genotyping for NAT1*3 , NAT1*4 , NAT1*10 , NAT1*11 and NAT1*14 showed that genotypes containing the rapid acetylator NAT1*10 allele were under-represented in PPD-sensitized cases (adjusted odds ratio 0·72, 95% confidence interval 0·45–1·16). For NAT2 , NAT2*4 , NAT2*5AB , NAT2*5C , NAT2*6A and NAT2*7B alleles were genotyped. Individuals homozygous for the rapid acetylator allele NAT2*4 were under-represented in cases compared with controls (4·3% vs. 9·4%), but this trend was not significant.
Conclusions  With respect to data indicating that NAT1 but not NAT2 is present in human skin, we conclude that NAT1 genotypes containing the rapid acetylator NAT1*10 allele are potentially associated with reduced susceptibility to PPD sensitization.     

Das Verhältnis von Klinikum und Fakultät

The relationship between German university hospitals and medical schools is mainly based on the cooperation model; in a few cases the integration model is applied. Both models bear characteristic advantages and disadvantages; in the cooperation model, e.g., processes might be slowed down by a multitude of regulatory mechanisms. The integration model supports a close connection of the medical school and university hospital. Currently, legislation concerning university medicine in Germany shows a trend to increase the influence of the government and the university president within the balance of power. Therefore, the cooperation model is still favored. In order that university hospitals remain sustainable for the future, especially in terms of research, site-specific solutions have to be developed and legitimated.     

Ekkrines Porokarzinom neben multiplen anderen epithelialen Hauttumoren

Ohne Zusammenfassung