Dapsone‐ and nitroso dapsone‐specific activation of T cells from hypersensitive patients expressing the risk allele HLA‐B*13:01

BACKGROUND:Research into drug hypersensitivity associated with expression of specific HLA alleles has focussed on the interaction between parent drug and the HLA with no attention given to reactive metabolites. For this reason, we have studied HLA-B*13:01-linked dapsone hypersensitivity to (1) explore whether the parent drug and/or nitroso metabolite activates T-cells and (2) determine whether HLA-B*13:01 is involved in the response. METHODS:PBMC from 6 patients were cultured with dapsone and nitroso dapsone and proliferative responses and IFN-γ release were measured. Dapsone- and nitroso dapsone-specific T-cell clones were generated and phenotype, function, HLA allele restriction and cross-reactivity assessed. Dapsone intermediates were characterized by mass spectrometry. RESULTS:PBMC from 6 patients and cloned T-cells proliferated and secreted Th1/2/22 cytokines when stimulated with dapsone (clones: n=395; 80% CD4+ CXCR3hi CCR4hi , 20% CD8+CXCR3hi CCR4hi CCR6hi CCR9hi CCR10hi ) and nitroso dapsone (clones: n=399; 78% CD4+, 22% CD8+ with same chemokine receptor profile). CD4+ and CD8+ clones were HLA-class II and class I restricted, respectively, and displayed three patterns of reactivity: compound-specific, weakly crossreactive and strongly cross reactive. Nitroso dapsone formed dimers in culture and was reduced to dapsone, providing a rationale for the crossreactivity. T-cell responses to nitroso dapsone were dependent on the formation of a cysteine-modified protein adduct, while dapsone interacted in a labile manner with antigen presenting cells. CD8+ clones displayed an HLA-B*13:01-restricted pattern of activation. CONCLUSION:These studies describe the phenotype and function of dapsone- and nitroso dapsone-responsive CD4+ and CD8+ T-cells from hypersensitive patients. Discovery of HLA-B*13:01-restricted CD8+ T-cell responses indicates that drugs and their reactive metabolites participate in HLA allele-linked forms of hypersensitivity. This article is protected by copyright. All rights reserved

Seroepidemiology of Toxoplasma gondii infection in pregnant women in a public hospital in northern Mexico

BACKGROUND: Toxoplasma gondii (T. gondii) infection in pregnant women represents a risk for congenital disease. There is scarce information about the epidemiology of T. gondii infection in pregnant women in Mexico. Therefore, we sought to determine the prevalence of T. gondii infection and associated socio-demographic, clinical and behavioural characteristics in a population of pregnant women of Durango City, Mexico. METHODS: Three hundred and forty three women seeking prenatal care in a public hospital of Durango City in Mexico were examined for T. gondii infection. All women were tested for anti-T. gondii IgM and IgG antibodies by using IMx Toxo IgM and IMx Toxo IgG 2.0 kits (Abbott Laboratories, Abbott Park, IL, USA), respectively. Socio-demographic, clinical and behavioural characteristics from each participant were also obtained. RESULTS: Twenty one out of the 343 (6.1%) women had IgG anti-T. gondii antibodies. None of the 343 women had IgM anti-T. gondii antibodies. Multivariate analysis using logic regression showed that T. gondii infection was associated with living in a house with soil floor (adjusted OR = 7.16; 95% CI: 1.39–36.84), residing outside of Durango State (adjusted OR = 4.25; 95% CI: 1.72–10.49), and turkey meat consumption (adjusted OR = 3.85; 95% CI: 1.30–11.44). Other characteristics as cat contact, gardening, and food preferences did not show any association with T. gondii infection. CONCLUSION: The prevalence of T. gondii infection in pregnant women of Durango City is low as compared with those reported in other regions of Mexico and the majority of other countries. Poor housing conditions as soil floors, residing in other Mexican States, and turkey meat consumption might contribute to acquire T. gondii infection

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

Electron transport and effective ionization coefficients in C2F6, C2F6-Ar and C2F6-N-2 mixtures

The electron drift velocity, the longitudinal diffusion coefficient and the effective ionization coefficients in CF and its mixtures with Ar and N have been studied in a pulsed Townsend experiment. The density-reduced electric field strength E/N, was varied widely in the range 0.1-500 Td (1 Td = 10 V cm). In all cases, negative differential conductivity (NDC) regions were found in the plots of the electron drift velocity as a function of E/N. Our drift velocity values were found to be in good agreement with previous work on CF and its mixtures. In some cases, the E/N range was increased. The longitudinal diffusion coefficient also displays the NDC effects; these are more pronounced as the CF content in the mixture decreases. The effective ionization coefficient for CF was measured over a wider range of E/N than that covered by previous studies. Our effective ionization coefficients for CF, and those derived previously disagree strongly. We are not aware of any previously published data on effective ionization coefficients for the mixtures herein studied. The limiting field strength for CF-N turned out to be nearly a factor of two higher than that for CF-Ar, for CF concentrations being less than 10% in both mixtures

Electron drift velocities in mixtures of helium and xenon and experimental verification of corrections to Blanc's law

Measurements of electron drift velocities were performed in pure Xe and He and in a number of mixtures ranging up to 70% of Xe. The data were obtained by using a pulsed Townsend technique over the density-normalized electric field strength E/N between 1 and 100 Td. Even for pure gases there are no data in the entire range covered here, and these data represent an extension of accurate drift velocities to higher E/N. A selection of well-established cross sections for low energies, which was extended to higher energies, led to a reasonably good agreement of the calculated transport coefficients with the available data. At the same time we have applied the standard (common E/N) Blanc's law and two forms of common mean energy (CME, due to Chiflykian) procedures. Blanc's law fails for most mixtures at low and moderate E/N, while the CME procedure is capable of following the experimental data for the mixtures much more closely, and even predicting the negative differential conductivity region when such effect does not exist for pure gases. Thus the present paper also represents an experimental test of procedures to correct the standard Blanc's law. Finally, we have used the data for two mixtures to obtain results for the third mixture and in all cases this procedure gave excellent results even though only the standard Blanc's law was used in the process