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(1/408) Inhibition of allergic contact dermatitis to DNCB but not to oxazolone in interleukin-4-deficient mice.

The role of interleukin-4 as a regulator of immune responses in the skin is investigated with regard to the outcome of contact hypersensitivity reaction in interleukin-4-deficient BALB/C mice. In previous studies conflicting results were obtained concerning the role of interleukin-4 in contact hypersensitivity reactions supporting either a proinflammatory or rather an inhibitory function of this cytokine. Interleukin-4 deficient BALB/C mice sensitized to 2,4-dinitrochlorobenzene showed after challenge a significant reduction in magnitude and duration of the contact hypersensitivity response in comparison with wild-type mice. This attenuation was accompanied by a significant reduction of edema and cellular infiltrates in the dermis and a lacking induction of IL-10 mRNA expression in skin. Also, adoptive transfer experiments revealed that BALB/C mice failed to exhibit contact hypersensitivity after injection of lymph node cells obtained from sensitized interleukin-4 deficient mice. To examine further the role of the contact allergen used to induce the contact hypersensitivity response, mice were also sensitized and challenged with Oxazolone. Here a similar magnitude and duration of contact hypersensitivity in both the interleukin-4 deficient mice and BALB/C control mice was observed. This indicates that the contact hypersensitivity response to 2,4-dinitrochlorobenzene and Oxazolone may partly evolve on different pathways being dependent and independent of interleukin-4. Our results clearly show that the complete loss of endogenous interleukin-4 expression in BALB/C mice is associated with an impaired manifestation of contact hypersensitivity response to 2,4-dinitrochlorobenzene, implying an important proinflammatory function of this cytokine.  (+info)

(2/408) Direct Ni2+ antigen formation on cultured human dendritic cells.

The possible direct antigen formation of Ni2+ on antigen-presenting cells (APCs) was studied with cultured human dendritic cells (DCs) obtained from 10 subjects contact allergic to Ni2+ and six non-allergic control individuals. All contact allergic subjects showed a significantly increased peripheral blood mononuclear cell (PBMC) response in vitro to Ni2+. DCs were expanded from the plastic-adherent cell fraction of PBMCs by culturing with granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4) for 7 days to obtain immature DCs, and with the addition of monocyte-conditioned medium for another 4 days, for DC maturation. The DCs were pulsed for 20 min with Ni2+ (50 micrometers) in protein-free Hank's balanced salt solution (HBSS) and added to freshly prepared autologous responder PBMCs. With five allergic subjects, immature DCs pulsed with Ni2+ demonstrated a significant capacity to activate Ni2+-reactive lymphocytes. With the remaining five patients and the six controls no difference in lymphocyte proliferation was observed between Ni2+-pulsed and non-pulsed immature DCs. In contrast, with mature Ni2+-pulsed DCs from both 'positive responder' (n=4) and 'non-responder' (n=4) patients, there was a significantly stimulated PBMC proliferation, whereas with the controls (n=4) still no activation was observed. Our results indicate that direct formation of the antigenic determinant of Ni2+ on APCs is possible and that Ni2+ uptake and processing mechanisms may not play a major role. Differences in the ease of activation of Ni2+-reactive lymphocytes are discussed in terms of a possible heterogeneity in the availability of Ni2+-reactive groups presented on endogenous peptides bound in the antigen binding groove of human leucocyte antigen (HLA) class-II molecules.  (+info)

(3/408) Early changes in murine epidermal cell phenotype by contact sensitizers.

In order to develop an in vitro predictive assay for the detection of contact sensitizers, we investigated the possible modulation of the expression of cell-surface molecules in the early phases of treatment of murine epidermal cells (EC) with known contact sensitizers. After in vitro treatment of Balb/c EC with the strong contact sensitizer, TNBS, Langerhans cells (LCs) demonstrated a rapid up-regulation of CD45, CD40, CD32/16 (Fc gamma RII/III) and CD23 (Fc epsilon RII) molecules. CD45 and CD40 were also rapidly up-regulated on the dendritic epidermal T cells. Interestingly, after treatment with this severe sensitizer, a marked induction of CD40 expression was found on a CD45 negative population, most probably keratinocytes. In contrast to these cell-surface molecules, I-Ad/I-Ed and CD90.2 expression were unchanged. No change was observed on the expression of CD45 and CD40 after treatment with a mild or a weak contact sensitizer, citral and citronellal respectively. In contrast, like TNBS, they up-regulated the expression of CD32/16 and CD23 on LCs. The irritant sodium dodecyl sulfate had no effect on all these cell-surface molecules. Our results indicated that in vitro, chemicals with allergic potential induced early specific phenotype changes that may represent an early-activated state of the cells. This state may be responsible for initiating the afferent phase of contact sensitivity in vivo. Based on these findings, it might be possible to develop an in vitro assay to reduce the number of experimental animals for a fast screening of contact sensitizers and for discriminating between mild contact sensitizers and irritants.  (+info)

(4/408) Low-dose UVA and UVB have different time courses for suppression of contact hypersensitivity to a recall antigen in humans.

This study investigates the relative effects of low-dose solar-simulated ultraviolet, ultraviolet A, and ultraviolet B radiation on the elicitation of contact hypersensitivity to nickel in nickel-allergic volunteers. A xenon arc lamp with changeable filters was used to irradiate groups of volunteers daily, on separate areas of their lower backs, with both solar-simulated ultraviolet (ultraviolet B, ultraviolet AII + ultraviolet AI) and ultraviolet A (same ultraviolet AII content but twice the ultraviolet AI as the solar-simulated ultraviolet spectrum) for 1 and 2 d; 3, 4, and 5 d; and from 1 to 4 wk. A fourth group was irradiated for 1-5 d with the ultraviolet B component of solar-simulated ultraviolet. Following the final irradiation in each group, nickel-containing patches were applied to both ultraviolet-treated sites and adjacent, unirradiated control sites. Erythema caused by nickel contact hypersensitivity at each site was quantitated 72 h later with a reflectance erythema meter. By comparing the nickel reactions of irradiated and unirradiated skin, ultraviolet immunosuppression was assessed with the different spectra and durations of ultraviolet exposure. We found significant immunosuppression with daily doses of ultraviolet B and ultraviolet A equivalent to approximately 6 min of summer sun exposure, and that ultraviolet A and ultraviolet B exerted their maximal immunosuppressive effects at different times. Solar-simulated ultraviolet-induced immunosuppression was significant after one exposure, near-maximal after two exposures and remained elevated thereafter. Ultraviolet B-induced immunosuppression was lower than that induced by solar-simulated ultraviolet, but followed a similar time-course. In contrast, ultraviolet A-induced immunosuppression was transient, peaking after three exposures. Immune responses returned towards normal with subsequent ultraviolet A exposure, suggesting that an adaptive mechanism may prevent immunosuppression by continued ultraviolet A irradiation.  (+info)

(5/408) Nickel allergy in mice: enhanced sensitization capacity of nickel at higher oxidation states.

Attempts to induce contact hypersensitivity to nickel in mice using, e.g., Ni(II)Cl2 often failed. Here, we report that sensitization was achieved by injecting Ni(II)Cl2 in combination with either CFA or an irritant, such as SDS and PMA, or IL-12, or by administering nickel at higher oxidation states, i.e., Ni(III) and Ni(IV). Although Ni(II), given alone, was ineffective in T cell priming, it sufficed for eliciting recall responses in vivo and in vitro, suggesting that Ni(II) is able to provide an effective signal 1 for T cell activation, but is unable to provide an adequate signal 2 for priming. Immunization of mice with nickel-binding proteins pretreated with Ni(IV), but not with Ni(II), allowed them to generate nickel-specific CD4+ T cell hybridomas. Ni(II) sufficed for restimulation of T cell hybridomas; in this and other aspects as well, the hybridomas resembled the nickel-specific human T cell clones reported in the literature. Interestingly, restimulation of hybridomas did not require the original Ni(IV)-protein complex used for priming, suggesting either that the nickel ions underwent ligand exchange toward unknown self proteins or peptides or that nickel recognition by the TCR is carrier-independent. In conclusion, we found that Ni(III) and Ni(IV), but not Ni(II) alone, were able to sensitize naive T cells. Since both Ni(III) and Ni(IV) can be generated from Ni(II) by reactive oxygen species, released during inflammation, our findings might explain why in humans nickel contact dermatitis develops much more readily in irritated than in normal skin.  (+info)

(6/408) Dental surgeons with natural rubber latex allergy: a report of 20 cases.

Latex allergy is becoming a major occupational health issue and dental surgeons are at risk from becoming sensitized to natural rubber latex. A study was conducted to investigate risk factors and glove-related symptoms reported by dentists with natural rubber latex allergy. Twenty dentists, who had undergone serological or dermatological testing for a Type I allergy to latex, were identified from a questionnaire survey. Risk factors investigated were: gender, years in clinical practice, exposure to latex gloves, atopic history and food allergy. The majority of dentists (75%) gave an atopic history. Glove-related adverse reactions ranged from cutaneous to systemic manifestations. All twenty dentists reported itching of the hands in response to latex gloves. One respondent was unable to continue in dental practice because of her glove-related allergies; nineteen dentists were able to continue by using synthetic, non-latex gloves.  (+info)

(7/408) TCR reactivity in human nickel allergy indicates contacts with complementarity-determining region 3 but excludes superantigen-like recognition.

Nickel is the most common inducer of contact sensitivity in humans. We previously found that overrepresentation of the TCRBV17 element in Ni-induced CD4+ T cell lines of Ni-allergic patients relates to the severity of the disease. Amino acid sequences of these beta-chains suggested hypothetical contact points for Ni2+ ions in complementarity-determining region (CDR) 1 and CDR3. To specifically address the molecular requirements for Ni recognition by TCR, human TCR alpha- and beta-chains of VB17+ Ni-reactive T cell clones were functionally expressed together with the human CD4 coreceptor in a mouse T cell hybridoma. Loss of CD4 revealed complete CD4 independence for one of the TCR studied. Putative TCR/Ni contact points were tested by pairing of TCR chains from different clones, also with different specificity. TCRBV17 chains with different J regions, but similar CDR3 regions, could be functionally exchanged. Larger differences in the CDR3 region were not tolerated. Specific combinations of alpha- and beta-chains were required, excluding a superantigen-like activation by Ni. Mutation of amino acids in CDR1 of TCRBV17 did not affect Ag recognition, superantigen activation, or HLA restriction. In contrast, mutation of Arg95 or Asp96, conserved in many CDR3B sequences of Ni-specific, VB17+ TCR, abrogated Ni recognition. These results define specific amino acids in the CDR3B region of a VB17+ TCR to be crucial for human nickel recognition. CD4 independence implies a high affinity of such receptor types for the Ni/MHC complex. This may point to a dominant role of T cells bearing such receptors in the pathology of contact dermatitis.  (+info)

(8/408) The CXCR3 activating chemokines IP-10, Mig, and IP-9 are expressed in allergic but not in irritant patch test reactions.

Differentiation between allergic and irritant contact dermatitis reactions is difficult, as both inflammatory diseases are clinically, histologically, and immunohistologically very similar. Previous studies in mice revealed that the chemokine IP-10 is exclusively expressed in allergic contact dermatitis reactions. In the present study, we investigated whether the mRNA expression of IP-10 and the related CXCR3 activating chemokines, Mig and IP-9 are also differentially expressed in human allergic contact dermatitis and irritant contact dermatitis reactions. Skin biopsies from allergic (13 cases) and sodium lauryl sulfate-induced irritant patch test reactions (13 cases), obtained 1-72 h after patch testing, were studied by means of an in situ hybridization technique. Results of chemokine mRNA expression were correlated with clinical scoring, histology, and immunohistochemical data including the proportion of inflammatory cells expressing CXCR3, the receptor for IP-10, Mig, and IP-9, and ICAM-1 and HLA-DR expression on keratinocytes. IP-10, Mig, and IP-9 mRNA were detected in seven of nine allergic contact dermatitis reactions after 24-72 h, but not in sodium lauryl sulfate-induced irritant contact dermatitis reactions. ICAM-1 expression by keratinocytes was only found in allergic contact dermatitis reactions and correlated with chemokine expression. Moreover, up to 50% of the infiltrating cells in allergic contact dermatitis expressed CXCR3, in contrast to only 20% in irritant contact dermatitis reactions. In conclusion, we have demonstrated differences in chemokine expression between allergic contact dermatitis and irritant contact dermatitis reactions, which might reflect different regulatory mechanisms operating in these diseases and may be an important clue for differentiation between allergic contact dermatitis and irritant contact dermatitis reactions.  (+info)