Diminished contact hypersensitivity response in IL-4 deficient mice at a late phase of the elicitation reaction

Contact hypersensitivity (CHS) is thought to depend on the activation of T cells of Th1 and/or Tc1 type. The role of Th2/Tc2 cells in the contact allergic reaction is not clear. The aim of this study was to analyse the functional contribution of Th2/Tc2 cells in CHS using the interleukin-4 (IL-4) deficient mouse model. Interleukin-4 deficient (IL4T) and control (wt) mice were sensitized by epicutaneous application of 2,4-dinitrofluorobenzene. The ear swelling response measured 24 h after challenge was similar in IL4T and control mice. However, from 48 h onwards, ear swelling values were significantly reduced in IL4T mice. The stimulatory capacity of freshly isolated as well as 3-day cultured epidermal cells, prepared from IL4T and wt mice, for allogeneic T cells in a primary and secondary response, was comparable. The reduced number of T cell receptor (TCR) gamma delta+ cells observed in epidermal sheets prepared from IL4T mice was not responsible for the decreased ear swelling response in IL4T mice, because the use of TCR delta deficient mice lacking TCR gamma delta+ cells revealed a down-regulatory role of this cell population in the CHS response. The data indicate that the effector stage of the CHS response can be subdivided into two phases. The first phase proceeds efficiently in IL-4 deficient mice indicating the dependence on Th1/Tc1 cells, while the second phase does not develop in mice lacking IL-4, suggesting the possibility that Th2/Tc2 cells intensify the reaction.

Immunostimulatory effects of platinum compounds: correlation between sensitizing properties in vivo and modulation of receptor-mediated endocytosis in vitro

The sensitizing properties of different complex salts of platinum were defined in vivo by means of the popliteal lymph node (PLN) assay in mice. Hexa- and tetrachloroplatinates were confirmed to be highly immunogenic, inducing vigorous primary immune responses in the draining PLN following single subcutaneous injections. Flow-cytometric analysis revealed a dramatic increase in the total number of cells expressing proliferating cell nuclear antigen. The majority of these cells were of the T helper phenotype (CD4+) reflecting the T-cell dependence of the PLN response induced by Pt salts such as Na2[PtCl6] or Na2[PtCl4]. In contrast, [Pt(NH3)4]Cl2 failed to elicit a significant increase in PLN cell proliferation when compared with saline-treated controls. The differential immunogenicity of the Pt compounds found in vivo directly correlated with their capacity to modulate mechanisms of receptor-mediated endocytosis in murine Langerhans cells in vitro. The reactivity of Na2[PtCl6] or Na2[PtCl4] resembled that of potent contact sensitizers in this endocytosis assay whereas [Pt(NH3)4]Cl2 proved to be mert. These results suggest that [Pt(NH3)4]Cl2 might be less harmful to humans than hexa- or tetrachloroplatinates. As demonstrated with Pt compounds, monitoring of direct effects of low-molecular-weight chemicals on antigen-presenting dendritic cells in vitro is able to predict their sensitizing potential in vivo.

Cytokines and their effects on maturation, differentiation and migration of dendritic cells

In this review the role of cytokines in the maturation and migration of phenotypically and functionally diverse dendritic cell (DC) subpopulations is discussed and their role in progress of differentiation from bone marrow progenitors to lymphoid DC is described. GM-CSF is the most important cytokine for the development of functional DC and acts in concert with a varying mixture of other cytokines such as IL-4, IL-1 and TNF-alpha to direct the development of individual DC subpopulations.

Specific stabilization of the 4F7 molecule on dendritic cells by contact allergens

Our laboratory has recently developed the monoclonal antibody 4F7 which recognizes a molecule on dendritic cells in the dermis of mice that is upregulated after application of contact allergens in vivo. Furthermore, this antibody detects an antigen on dendritic cells in spleen, lymph nodes and colon. In order to study the influence of contact allergens on the surface expression of the 4F7 molecules on dendritic cells, FACScan analysis of splenic dendritic cells was carried out after in vitro application of contact allergens. Freshly isolated splenic dendritic cells were found to be positive for 4F7, 33D1, N418 (CD11c) and MHC class II. After overnight culture the expression of the dendritic cell-specific molecules 4F7 and 33D1 was decreased. This downregulation was not inhibited by the addition of the cytokines TNF-alpha or GM-CSF during in vitro culture. However, in vitro treatment of freshly isolated dendritic cells with the contact allergen 2,4-dinitrofluorobenzene prevented this downregulation of the 4F7 surface molecules. The same effect was observed after treatment with other contact allergens (1-chloro-2,4-dinitrobenzene or potassium dichromate). Treatment with the irritant substance sodium dodecyl sulphate, the lectins concanavalin and lipopolysaccharide or the phorbol ester PMA did not prevent the downregulation of 4F7 and 33D1. Moreover, the influence of contact allergens on the expression of the molecules 4F7 and 33D1 was not inhibited by the protein synthesis inhibitor cycloheximide. No effects of contact sensitizers were detectable on the expression of MHC class II molecules or the costimulatory molecules B7 and heat-stable antigen. Our results show a specific stabilizing effect of contact allergens on the dendritic cell-specific molecules 4F7 and 33D1 independent of de novo protein synthesis.

TAP-polymorphisms in juvenile onset psoriasis and psoriatic arthritis

Juvenile onset psoriasis is strongly associated with the HLA-class I genes Cw6 and B57 whereas patients with psoriatic arthritis show an increased frequency of HLA-B27. It is unclear whether additional major histocompatibility genes also increase disease susceptibility. The TAP genes (transporter associated with antigen processing) encode two membrane-spanning proteins that translocate antigenic peptides from the cytoplasm into the endoplasmic reticulum. Comparison of 60 patients with juvenile onset psoriasis, 63 psoriatic arthritis patients, and 101 caucasoid controls revealed an increase of the TAP1*0101 allele in the psoriasis group, that could not be explained by linkage to other investigated HLA genes. There were no differences for TAP2 alleles.

Epidermal cells enhance interleukin 4 and immunoglobulin E production after stimulation with protein allergen

Exposure to certain allergens via epithelial tissues is the primary route for the induction of immunoglobulin E-dependent allergies of the immediate type associated with atopic diseases. In order to address the question whether and how epithelial cells might contribute to the induction or increase of TH2-dependent IgE production, we performed co-culture experiments of syngeneic epidermal cells and cells from the associated lymphoid tissue or spleen (responder cells) of BALB/c mice primed with ovalbumin in vivo. In the presence of ovalbumin in vitro, immunoglobulin E but not immunoglobulin G2a production was significantly enhanced by the addition of epidermal cells, and separation of epidermal cells from responder cells by a membrane that prevented cellular contacts or addition of antibodies against intercellular adhesion molecule-1 reduced the enhancement of immunoglobulin E production induced by epidermal cells. Depletion of major histocompatibility complex class II+ antigen presenting Langerhans cells from the epidermal cells prior to co-culture also reduced the enhancement of immunoglobulin E production induced by epidermal cells. The enhanced immunoglobulin E production was dependent on the induction of TH2 cell-derived interleukin-4 detected in co-cultures because it was completely inhibited after addition of anti-interleukin-4 antibodies that also lead to increased immunoglobulin G2a production. Whereas interleukin-4 was not produced by epidermal cells, interleukin-10 seemed to be one important mediator contributed by epidermal cells. Interleukin-10 skewed the response toward a TH2-mediated IgE response because antibodies against interleukin-10 inhibited interleukin-4 and immunoglobulin E production, whereas they enhanced interferon-gamma and immunoglobulin G2a production.

Is cytokine expression responsible for differences between allergens and irritants?

Irritant and allergic contact dermatitis are two very similar diseases, and differentiating between these two can be difficult clinically. Recently, cytokines have been identified as useful tools for differentiation. Thus, our laboratory has identified an early cytokine pattern in the induction phase of contact sensitivity that is specific for allergens and is not found after epicutaneous application of irritants or tolerogens. The up-regulation of the Langerhans' cell-derived signal interleukin (IL)-1 beta early after allergen application especially seems to be highly specific for contact allergens. This cytokine was also found to be essential for the development of epicutaneous sensitization because injection of an anti-IL-1 beta monoclonal antibody before epicutaneous application of an allergen prevented sensitization. Additionally, cytokines also seem to be involved in down-modulating an ongoing inflammatory reaction such as contact sensitivity. IL-10 especially was shown to inhibit the LC accessory functions and to down-modulate inflammatory cytokines. The homeostasis of proinflammatory and counterregulatory cytokines and their clinical implications are discussed in this review.

An approach to predictive testing of contact sensitizers in vitro by monitoring their influence on endocytotic mechanisms

Endocytotic activation of epidermal Langerhans cells (LC) by immunogenic haptens is an early event during development of allergic contact dermatitis. In this work a fast and objective flow-cytometric assay for predictive in vitro testing of contact sensitizers by monitoring their influence on endocytotic mechanisms in murine LC was developed. Epidermal cell suspensions were labelled with a monoclonal antibody directed to MHC class II molecules and pH-sensitive fluorochrome-coupled second-step reagents. For untreated LC a significant quenching of fluorescence intensity by internalization of the MHC-antibody complexes into acidic compartments was noticed. Similar results were obtained in the presence of irritants, the lectin concanavalin A and the phorbol ester phorbol 12-myristate 13-acetate. In contrast stimulation with several well-defined sensitizing compounds resulted in partial conservation of the fluorescence intensity due to the internalization of the labelled complexes into less acidic compartments. Monitoring this modulation of endocytosis is an effective in vitro method to test for properties typical for moderate and strong contact sensitizers. It will help to assess the risk of unknown chemicals to act as haptens and should be useful for restriction of animal experimentation in this field.

Superantigens

Superantigens are potent modulators of the immune system. Some of their biological and immunological properties are reviewed here with special attention to their potential significance for cutaneous inflammation, specific skin immune responses and skin diseases.

The electroencephalogram after alcohol administration in high-risk men and the development of alcohol use disorders 10 years later

BACKGROUND

In 1979 through 1980, electroencephalographic (EEG) responses to an alcohol challenge in 19 year-old sons of alcoholics as well as in sons of nonalcoholic control subjects were examined. The familial risk status of the subjects and greater EEG sensitivity to alcohol were hypothesized to predict the development of alcoholism 10 years later.

METHODS

In 1990 through 1992, diagnostic interviews were completed to ascertain alcohol and other substance use disorders in these subjects and to update their family history.

RESULTS

Updated family history of alcoholism predicted the development of substance dependence. Density of alcoholic relatives (the number of alcoholic relatives divided by the number of known relatives) was positively related to the severity of alcohol use disorders in the probands. Contrary to expectation, a greater EEG response at age 19 years was not related to the later development of alcohol dependence. Instead, the opposite was observed: a smaller EEG alpha frequency response to alcohol at age 19 years was related to the development of alcohol dependence and high quantity and frequency of alcohol consumption 10 years later.

CONCLUSIONS

Lower EEG response to a small dose of alcohol may be associated with the later development of alcohol dependence. This result is based on a small number of subjects and should be interpreted with caution. Although this result is opposite to our 1980 hypothesis, it is consistent with much of the recent literature.

IL-12 as mediator and adjuvant for the induction of contact sensitivity in vivo

To determine whether IL-12 serves as a regulator of contact sensitivity reactions, mice were painted with either 1.0% trinitrochlorobenzene or 0.5% dinitrofluorobenzene on abdominal skin. At various time points thereafter, regional lymph nodes or spleens were prepared for RNA extraction, and the signals for IL-12 p35 and p40 chain were sought by quantitative reverse transcriptase-PCR. Time course analysis showed a constitutive expression of p35 chain mRNA signals throughout the experiment (0 to 72 h), whereas the signal for the p40 chain was transiently induced in lymph node and spleen cells after 12 to 14 h. Cellular depletion experiments and double label in situ hybridization studies showed that dendritic cells were sources for a major part of the p40 chain message. The presence of functional IL-12 in culture supernatants was indirectly assessed by addition of anti-IL-12 antiserum and analysis of IFN-gamma production. Significant amounts of IFN-gamma could only be detected in supernatants of allergen-treated animals. Addition of anti-IL-12 antiserum inhibited IFN-gamma production by about 55%. In a further attempt to assess the role of IL-12 in contact sensitivity, anti-IL-12 antiserum was injected i.p. into mice, and ear swelling responses were assessed following challenge. Injection of anti-IL-12 antiserum significantly reduced ear swelling responses by 85%. Thus anti-IL-12 treatment almost completely prevented sensitization. To assess whether IL-12 would be able to overcome in vivo tolerance, UV-tolerized animals were treated with i.p. IL-12 in a contact allergy system. Treatment of mice with IL-12 not only prevented tolerance induction, but was able to reverse UV-induced tolerance. In aggregate, our data point to an important role for IL-12 as a mediator and adjuvant for the induction of contact sensitivity in vivo.

IL-12 as mediator and adjuvant for the induction of contact sensitivity in vivo

To determine whether IL-12 serves as a regulator of contact sensitivity reactions, mice were painted with either 1.0% trinitrochlorobenzene or 0.5% dinitrofluorobenzene on abdominal skin. At various time points thereafter, regional lymph nodes or spleens were prepared for RNA extraction, and the signals for IL-12 p35 and p40 chain were sought by quantitative reverse transcriptase-PCR. Time course analysis showed a constitutive expression of p35 chain mRNA signals throughout the experiment (0 to 72 h), whereas the signal for the p40 chain was transiently induced in lymph node and spleen cells after 12 to 14 h. Cellular depletion experiments and double label in situ hybridization studies showed that dendritic cells were sources for a major part of the p40 chain message. The presence of functional IL-12 in culture supernatants was indirectly assessed by addition of anti-IL-12 antiserum and analysis of IFN-gamma production. Significant amounts of IFN-gamma could only be detected in supernatants of allergen-treated animals. Addition of anti-IL-12 antiserum inhibited IFN-gamma production by about 55%. In a further attempt to assess the role of IL-12 in contact sensitivity, anti-IL-12 antiserum was injected i.p. into mice, and ear swelling responses were assessed following challenge. Injection of anti-IL-12 antiserum significantly reduced ear swelling responses by 85%. Thus anti-IL-12 treatment almost completely prevented sensitization. To assess whether IL-12 would be able to overcome in vivo tolerance, UV-tolerized animals were treated with i.p. IL-12 in a contact allergy system. Treatment of mice with IL-12 not only prevented tolerance induction, but was able to reverse UV-induced tolerance. In aggregate, our data point to an important role for IL-12 as a mediator and adjuvant for the induction of contact sensitivity in vivo.

Ultraviolet B radiation up-regulates the expression of IL-15 in human skin

Ultraviolet B (UVB) radiation is a potent modulator of skin-related immune responses, particularly those involving the synthesis and the secretion of cytokines. The discovery of a new T cell mitogen, IL-15, prompted use to investigate its expression in skin and to examine the effects of UVB radiation on such expression. RNA from unirradiated and UVB-irradiated epidermal and dermal sheets derived from human foreskin as well as from unirradiated and UVB-irradiated skin cell populations were assayed for IL-15 expression by semiquantitative RT-PCR. Constitutive levels of IL-15 mRNA were detected in dermal sheets, but not in epidermal sheets. Following UVB treatment, IL-15 mRNA was induced in epidermal sheets and enhanced in dermal sheets. UVB-inducible epidermal expression of IL-15 mRNA was traced to HLA-DR- cells (presumably keratinocytes) and not to HLA-DR+ cells (Langerhans cells). Cultured keratinocytes and dermal fibroblasts displayed basal levels of IL-15 mRNA that were also up-regulated following UVB exposure. Immunoblot analysis revealed secretion of IL-15 protein by keratinocytes that was enhanced following UVB treatment. These results constitute the first report of IL-15 mRNA expression and protein production in human skin. In addition to expanding the known influence of UVB radiation on the capacity of keratinocytes and dermal fibroblasts to express immunomodulatory cytokines, these findings suggest a new mechanism by which UVB can promote Ag-independent T cell responses via elaboration of IL-15.

Ultraviolet B radiation up-regulates the expression of IL-15 in human skin

Ultraviolet B (UVB) radiation is a potent modulator of skin-related immune responses, particularly those involving the synthesis and the secretion of cytokines. The discovery of a new T cell mitogen, IL-15, prompted use to investigate its expression in skin and to examine the effects of UVB radiation on such expression. RNA from unirradiated and UVB-irradiated epidermal and dermal sheets derived from human foreskin as well as from unirradiated and UVB-irradiated skin cell populations were assayed for IL-15 expression by semiquantitative RT-PCR. Constitutive levels of IL-15 mRNA were detected in dermal sheets, but not in epidermal sheets. Following UVB treatment, IL-15 mRNA was induced in epidermal sheets and enhanced in dermal sheets. UVB-inducible epidermal expression of IL-15 mRNA was traced to HLA-DR- cells (presumably keratinocytes) and not to HLA-DR+ cells (Langerhans cells). Cultured keratinocytes and dermal fibroblasts displayed basal levels of IL-15 mRNA that were also up-regulated following UVB exposure. Immunoblot analysis revealed secretion of IL-15 protein by keratinocytes that was enhanced following UVB treatment. These results constitute the first report of IL-15 mRNA expression and protein production in human skin. In addition to expanding the known influence of UVB radiation on the capacity of keratinocytes and dermal fibroblasts to express immunomodulatory cytokines, these findings suggest a new mechanism by which UVB can promote Ag-independent T cell responses via elaboration of IL-15.

Prevention and reversal of superantigen-induced anergy by contact allergen exposure

The superantigen Staphylococcal enterotoxin B (SEB) and the contact allergen 2,4-dinitrofluorbenzene (DNFB) both react with V beta 8+ T-cells delivering distinct signals. Pre-treatment with DNFB painted onto the same skin site where SEB was to be injected, prevented the induction of anergy in V beta + T-cells that was otherwise induced after SEB had been injected intradermally over a period of 2 weeks. Application of the irritant sodium dodecyl sulfate (SDS) instead of DNFB did not exert this effect. Application of DNFB at a site distant from the site where SEB was injected resulted in a much weaker inhibitory influence on the induction of anergy by SEB. Established anergy of V beta 8+ T-cells (proliferative non-responsiveness to SEB in vitro that could be overcome by addition of exogenous interleukin 2 (IL-2)) could be largely reversed by repeated cutaneous exposure to DNFB painted to the site where SEB had been injected before. The moderate decrease of V beta 8+ T-cells normally induced by SEB-treatment was also partially prevented by DNFB pre-treatment. The data indicate the importance of the sequence of signals delivered to T cells and the plasticity of the responsiveness of this cell type.

Heat-stable antigen is expressed by murine keratinocytes and delivers costimulatory signals in T-cell activation

Heat-stable antigen (HSA), expressed by various antigen-presenting cells (APC), has been described as a costimulatory molecule for CD4+ T cells. Recently, we observed that HSA also serves as an important costimulatory molecule on epidermal Langerhans cells (LC). During these studies, low levels of HSA staining were also detected on normal murine keratinocytes (KC). To investigate whether HSA also is involved in T-cell activation by KC, normal murine KC or the spontaneously transformed KC cell-line PAM 212 were treated with PDB or PMA to induce HSA-expression. FACS analyses showed induction of HSA expression on normal murine KC, as well as PAM 212 cells. In functional assays PDB or PMA-treated normal or transformed KC were far more potent inducers of primary allogeneic T-cell responses than untreated KC. Addition of anti-HSA-specific mAb 20C9 specifically inhibited the costimulatory activity of KC, an effect that was even more pronounced when CTLA-4Ig was added to the cultures. Cleavage of HSA on KC surfaces by a phosphoinositol-specific phospholipase C (PI-PLC) also significantly inhibited the costimulatory capacity of KC for naive CD4+ T cells. In aggregate, our data indicate that expression of HSA on activated KC contributes to the capacity of these cells to induce proliferation of allogeneic T cells.

Activation of murine epidermal TCR-gamma delta+ T cells by keratinocytes treated with contact sensitizers

The vast majority of TCR gamma delta+, CD4-, CD8- T cells resident in the adult mouse epidermis expresses tissue-specific V-region genes (V gamma 3/V delta 1) in the absence of junctional diversity. The role this unique T cell population plays in the immune surveillance of the skin is not clear. It has been shown that dendritic epidermal T cells (DETC) were activated by stressed keratinocytes and that stimulated DETC produced, for example, a keratinocyte-specific growth factor. To investigate whether DETC are involved in the induction of a contact allergy, we examined the influence of contact sensitizers and nonsensitizing contact irritants on the DETC response toward epidermal symbionts. We show that 9 of 15 cloned DETC are specifically activated, apparently in a non-MHC-restricted way, to proliferate in the presence of keratinocytes or unseparated epidermal cells, which were treated with a sensitizing agent either in vivo or in vitro. All seven tested contact sensitizing substances activated all of the reactive DETC, while keratinocytes/epidermal cells treated with nonsensitizing irritants were as nonstimulatory as vehicle controls. We demonstrate that direct cell to cell contact of DETC and stimulatory keratinocytes/epidermal cells was required and that the TCR was involved in the induction of DETC proliferation. This specific reactivity of DETC toward keratinocytes or epidermal cells pretreated with a contact sensitizer may be indicative of participation of epidermal T cells in the induction of a contact sensitivity and points to a possible role of DETC in the skin immune system.

Activation of murine epidermal TCR-gamma delta+ T cells by keratinocytes treated with contact sensitizers

The vast majority of TCR gamma delta+, CD4-, CD8- T cells resident in the adult mouse epidermis expresses tissue-specific V-region genes (V gamma 3/V delta 1) in the absence of junctional diversity. The role this unique T cell population plays in the immune surveillance of the skin is not clear. It has been shown that dendritic epidermal T cells (DETC) were activated by stressed keratinocytes and that stimulated DETC produced, for example, a keratinocyte-specific growth factor. To investigate whether DETC are involved in the induction of a contact allergy, we examined the influence of contact sensitizers and nonsensitizing contact irritants on the DETC response toward epidermal symbionts. We show that 9 of 15 cloned DETC are specifically activated, apparently in a non-MHC-restricted way, to proliferate in the presence of keratinocytes or unseparated epidermal cells, which were treated with a sensitizing agent either in vivo or in vitro. All seven tested contact sensitizing substances activated all of the reactive DETC, while keratinocytes/epidermal cells treated with nonsensitizing irritants were as nonstimulatory as vehicle controls. We demonstrate that direct cell to cell contact of DETC and stimulatory keratinocytes/epidermal cells was required and that the TCR was involved in the induction of DETC proliferation. This specific reactivity of DETC toward keratinocytes or epidermal cells pretreated with a contact sensitizer may be indicative of participation of epidermal T cells in the induction of a contact sensitivity and points to a possible role of DETC in the skin immune system.

[Anaphylactic shock after lipid exchange chromatography in a patient with congenital IgA deficiency]

We report on a 59-year-old woman patient with selective IgA deficiency and familial hypercholesterinaemia. To lower elevated LDL levels in the patient's blood, immunoadsorption therapy with sheep-anti-human polyclonal antibodies coupled to sepharose columns was administered. During the procedure, the patient developed an anaphylactic shock requiring intensive care treatment. The patient's history revealed a fresh cell therapy with fetal sheep cells 10 years previously. Intracutaneous testing confirmed sensitization to sheep immunoglobulin, which was the most likely reason for the anaphylactic shock.

Contact sensitizers modulate mechanisms of receptor-mediated endocytosis but not fluid-phase endocytosis in murine epidermal Langerhans cells

In order to define the influence of contact allergens on the fluid-phase endocytosis (FPE) of soluble molecules of murine epidermal Langerhans cells (LC), we studied the internalization of FITC-labeled bovine serum albumin (FITC-BSA), TRITC-labeled dextrane (TRITC-DEX) as well as horseradish peroxidase by LC. A 3-parameter flow-cytometric technique was performed for quantification of internalized FITC-BSA in LC using quantum red-labeled reagents for detection of Ia-antigen expression by LC and propidium iodide for exclusion of dead cells from analysis. A temperature-dependent rapid accumulation of FITC-BSA was noticed in time-course studies reaching a plateau between 1 and 2 h of in vitro culture at 37 degrees C. The quantity of FPE under stimulation with phorbol 12-myristate 13-acetate (PMA), concanavalin A (Con A), staphylococcal enterotoxin B (SEB) and contact sensitizers (DNFB, Kathon CG, K2Cr2O7) as well as the irritant SLS was determined. Treatment of LC with PMA and Con A resulted in a significant increase of total FITC-BSA uptake. The contact sensitizers as well as SEB and SLS failed to mediate augmented fluid-phase endocytosis. By use of the pH-insensitive soluble marker, TRITC-DEX and a microscope photometer for evaluation these findings could be confirmed. This excluded any artificial influence of differences in pH values in endocytotic compartments which might have influenced the fluorescence intensity of the pH-sensitive fluorochrome FITC. For qualitative analysis of FPE, the intracellular distribution of internalized horseradish peroxidase in LC was studied. An aggregated pattern became apparent in untreated LC and did not change under stimulation with any of the substances used.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of contact sensitivity responses by bacterial superantigen

Superantigens are potent modulators of the immune system, especially T cells. Therefore, we determined the influence of superantigens on the T-cell-mediated immune response, contact sensitivity. We chose the combination of staphylococcal enterotoxin B (SEB) as superantigen and 2,4-dinitrofluorbenzene (DNFB) as the contact sensitizer, because in BALB/c mice SEB reacts almost exclusively with V beta 8+ T cells, and these cells are capable of transferring contact sensitivity to DNFB from sensitized donors to naive syngeneic recipients. Pretreatment with a single intradermal injection of 50 ng SEB 24 h before DNFB exposure at the same site on the lower abdomen enhanced the induction of contact sensitivity: its intradermal injection permitted sensitization with non-sensitizing concentrations of DNFB as assessed by ear swelling responses after challenge with DNFB. In contrast, pretreatment with repeated intradermal injections of 50 ng SEB every other day over at least 1 week inhibited the induction of contact sensitivity following sensitization. The enhancing effect of SEB may be explained by the creation of a proinflammatory milieu in the skin after a single intradermal injection of the bacterial toxin, whereas the inhibitory effect may be due to tolerization of V beta 8+ T cells. The data indicate that products of skin-colonizing bacteria that can serve as superantigens are able to augment or inhibit the development of contact sensitivity.

Activation of phenotypically heterogeneous murine T cell receptor gamma delta + dendritic epidermal T cells by self-antigen(s)

Adult murine epidermis contains a population of Thy-1+, CD45+, CD3+, CD4- and CD8- in situ primarily T cell receptor (TCR) V gamma 3+/V delta 1+ dendritic epidermal T cells (DETC). In the present study, cell surface phenotypes as well as functional properties of DETC were characterized by using in vitro mitogen-stimulated short-term- (10 days) and cloned long-term-cultured (> 1 year) DETC lines. Phenotypic characterization revealed that > 80% of the short-term-cultured cells were routinely TCR gamma delta +, CD4-, CD8-. The majority expressed the V gamma 3 TCR. Seventy-five percent of the lines contained detectable numbers of V gamma 2+ (5-7%) and V gamma 2-3- cells (2-3%). Four different types of stable TCR gamma delta +, CD4-, CD8- long-term-cultured clones were found: TCR V gamma 3+, V gamma 2+, V gamma 2-3- and V gamma 2-3-MHC-class-II+ clones. Nine of the 15 DETC clones tested were activated to proliferate in the presence of dendritic cells or macrophages, while keratinocytes were not stimulatory. This reactivity of DETC was mediated by the TCR and was apparently not MHC-restricted. Only the V gamma 3+, V gamma 2-3- or V gamma 2-3-MHC-class-II+DETC clones were self-responsive. Short-term-cultured DETC clones were self-responsive. Short-term-cultured DETC lines also exhibited the same reactivity. There was no specific cytokine profile of self-reactive DETC. Upon mitogen stimulation, short-term-cultured DETC lines secreted interleukin (IL)-2, IL-3, IL-4 and interferon (IFN)-gamma. In contrast, none of the long-term-cultured DETC clones produced IL-4. Four different profiles were discernible for the other lymphokines tested, irrespective of the clones' phenotype and reactivity towards accessory cells. The manifested profiles were IL-2, IL-3 and IFN-gamma, IL-2 and IL-3, IFN-gamma only and none of the tested lymphokines. The results suggest that DETC may comprise functionally different subsets and support the notion that DETC may exhibit immunorelevant activities in conjunction with natural neighboring cells.

[Cutaneous manifestations of essential thrombocythemia. Erythromelalgia, ischemic acrocyanosis, livedo racemosa]

A case report is presented to illustrate the cutaneous manifestations in essential thrombocythaemia. Knowledge of the related skin lesions may lead to earlier detection of this myeloproliferative disorder. Treatment may prevent severe haemorrhagic or thrombotic complications. Erythromelalgia is causally related to thrombocythaemia; prompt relief of painful symptoms after treatment with aspirin is typical.

Cellular and molecular mechanisms in the induction phase of contact sensitivity

During the induction phase of contact sensitivity, hapten-specific Th1 cells are primed by epidermal Langerhans cells. These Langerhans cells present hapten on MHC class II molecules and provide costimulatory signals. This presentation discusses the induction of cytokines in Langerhans cells and keratinocytes by haptens and their regulatory effects on contact sensitivity. Haptens were painted on the skin of normal BALB/c mice and epidermal cells were prepared at various times thereafter. Langerhans cell-derived interleukin (IL)-1 beta mRNA was observed as early as 15 min after hapten paining. In keratinocytes, tumor necrosis factor-alpha, IL-1 alpha, IP-10, MIP-2 and IL-10 were found to be up-regulated. IL-1 beta appeared to be a 'master' cytokine since it was able to mimic the effects of haptens, such as the increase of MHC class II expression in Langerhans cells and activation of the cytokine cascade. Injection of anti-IL-1 beta monoclonal antibody prior to hapten application completely prevented epicutaneous sensitization. In vivo application of IL-10 by intradermal injection prior to epicutaneous application of TNCB induced antigen-specific tolerance and impeded the induction of proinflammatory cytokines.