Elicitation of delayed allergic skin reactions with haptens; the dependence of elicitation on hapten combination with protein

Autism genes and the leukocyte transcriptome in autistic toddlers relate to pathogen interactomes, infection and the immune system. A role for excess neurotrophic sAPPα and reduced antimicrobial Aβ

Prenatal and early childhood infections have been implicated in autism. Many autism susceptibility genes (206 Autworks genes) are localised in the immune system and are related to immune/infection pathways. They are enriched in the host/pathogen interactomes of 18 separate microbes (bacteria/viruses and fungi) and to the genes regulated by bacterial toxins, mycotoxins and Toll-like receptor ligands. This enrichment was also observed for misregulated genes from a microarray study of leukocytes from autistic toddlers. The upregulated genes from this leukocyte study also matched the expression profiles in response to numerous infectious agents from the Broad Institute molecular signatures database. They also matched genes related to sudden infant death syndrome and autism comorbid conditions (autoimmune disease, systemic lupus erythematosus, diabetes, epilepsy and cardiomyopathy) as well as to estrogen and thyrotropin responses and to those upregulated by different types of stressors including oxidative stress, hypoxia, endoplasmic reticulum stress, ultraviolet radiation or 2,4-dinitrofluorobenzene, a hapten used to develop allergic skin reactions in animal models. The oxidative/integrated stress response is also upregulated in the autism brain and may contribute to myelination problems. There was also a marked similarity between the expression signatures of autism and Alzheimer's disease, and 44 shared autism/Alzheimer's disease genes are almost exclusively expressed in the blood-brain barrier. However, in contrast to Alzheimer's disease, levels of the antimicrobial peptide beta-amyloid are decreased and the levels of the neurotrophic/myelinotrophic soluble APP alpha are increased in autism, together with an increased activity of α-secretase. sAPPα induces an increase in glutamatergic and a decrease in GABA-ergic synapses creating and excitatory/inhibitory imbalance that has also been observed in autism. A literature survey showed that multiple autism genes converge on APP processing and that many are able to increase sAPPalpha at the expense of beta-amyloid production. A genetically programmed tilt of this axis towards an overproduction of neurotrophic/gliotrophic sAPPalpha and underproduction of antimicrobial beta-amyloid may explain the brain overgrowth and myelination dysfunction, as well as the involvement of pathogens in autism.

Carbamazepine-Mediated Adverse Drug Reactions: CBZ-10,11-epoxide but Not Carbamazepine Induces the Alteration of Peptides Presented by HLA-B∗15:02

Among patients treated with the anticonvulsive and psychotropic drug carbamazepine (CBZ), approximately 10% develop severe and life-threatening adverse drug reactions. These immunological conditions are resolved upon withdrawal of the medicament, suggesting that the drug does not manifest in the body in long term. The HLA allele B∗15:02 has been described to be a genomic biomarker for CBZ-mediated immune reactions. It is not well understood if the immune reactions are triggered by the original drug or by its metabolite carbamazepine-10,11-epoxide (EPX) and how the interaction between the drug and the distinct HLA molecule occurs. Genetically engineered human B-lymphoblastoid cells expressing soluble HLA-B∗15:02 molecules were treated with the drug or its metabolite. Functional pHLA complexes were purified; peptides were eluted and sequenced. Applying mass spectrometric analysis, CBZ and EPX were monitored by analyzing the heavy chain and peptide fractions separately for the presence of the drug. This method enabled the detection of the drug in a biological situation post-pHLA assembly. Both drugs were bound to the HLA-B∗15:02 heavy chain; however, solely EPX altered the peptide-binding motif of B∗15:02-restricted peptides. This observation could be explained through structural insight; EPX binds to the peptide-binding region and alters the biochemical features of the F pocket and thus the peptide motif. Understanding the nature of immunogenic interactions between CBZ and EPX with the HLA immune complex will guide towards effective and safe medications.

The Use of Diphenylcyclopropenone in the Treatment of Recalcitrant Warts

Background:

The treatment of recalcitrant palmoplantar and periungual warts using topical immunotherapy with diphenylcyclopropenone (DPC) was reviewed retrospectively over a seven-year period.

Methods:

Two hundred eleven patients were sensitized during this time. The patients consisted of 90 males and 121 females and were between 5 and 78 years old. Twenty-three patients were lost to followup. Of the remaining, 4 were undergoing treatment at the time of evaluation, 1 patient failed sensitization, and 1 patient became pregnant. Four discontinued because of side effects, 3 because of financial reasons, and 18 patients discontinued treatment prior to completing the minimum required applications (defined as 6), producing a dropout rate of 12% (25/211). Three patients had additional treatment during the course of DPC and were not included in the study. The remaining 154 patients were classified as nonresponders or responders.

Results:

The responders consisted of 135 individuals (87.7%) that had complete clearance of warts. Reported adverse effects were local and included with pruritus (15.6%), with blistering (7.1%), and with eczematous reactions (14.2%). The majority of the patients tolerated the treatment very well. One patient developed local impetigo. Patients had an average of 5 treatments over a 6-month period.

Conclusions:

Topical immunotherapy using DPC is an effective treatment option for recalcitrant warts. It should be considered as first-line treatment for warts based on its high response rate, absence of scarring, and painless application.

Seasonal variation of pheophorbide a and flavonoid in different organs of two Carpinus species and its correlation with immunosuppressive activity

The genus Carpinus of Betulaceae is the most widely distributed in the European landscape. This study reports a comparative study based on the pheophorbide a and flavonoid content from the two main species of the genus Carpinus, Carpinus betulus and Carpinus turczaninowii, respectively, in Nanjing, China. The pheophorbide a and flavonoid content depends on the organ, species, and season. HPLC analysis showed that the pheophorbide a and flavonoid levels were the highest in May and June, respectively, from the leaves of C. betulus 'Fastigiata.' In contrast, the content of pheophorbide a and flavonoid in the stems of C. betulus 'Fastigiata' or in other species was low. The immunosuppressive effects of the ethyl acetate extracts and methanol extracts from the two Carpinus species were also evaluated. The ethyl acetate extracts of C. betulus 'Fastigiata' in May and the methanol extracts of C. betulus 'Fastigiata' in June showed better immunosuppressive activity than in other seasons, which coincided with the content of pheophorbide a and flavonoid, respectively. Our findings indicated that C. betulus 'Fastigiata' can serve as a medicinal plant against inflammation because of its pheophorbide a and flavonoid content.

Contact Dermatitis, Patch Testing, and Allergen Avoidance

In patients presenting with a complaint of rash, contact dermatitis is often the underlying diagnosis making it an entity with which health care providers should be familiar. Contact dermatitis can be divided into irritant contact dermatitis and allergic contact dermatitis. In a patient suspected of having allergic contact dermatitis, patch testing can be done to identify specific allergens. Education focused on allergen avoidance and safe products is an integral part of treatment for the contact dermatitis patient. Knowledge of the most common allergens is helpful for clinicians to be able to provide this education.

Adverse Cutaneous Reactions and Drugs: A Focus on Antimicrobials

Rashes are a common adverse event observed during antimicrobial therapy. Many rashes are mild to moderate in intensity, however some reactions can be the prelude to much more severe outcomes such as Stevens-Johnson Syndrome (SJS) or Toxic Epidermal Necolysis. Several risk or influencing factors are known such as female gender, age and concomitant viral infections, and these may apply to more than one drug class. The incidence of rashes and other cutaneous reactions vary, however rates of >3% are reported with the beta-lactams while serious reactions such as SJS are observed with trimethoprim-sulphamethoxazole. Newer fluoroquinolone agents are devoid of the moiety which caused phototoxic reactions, while rates of rash vary from < 1%-3% or higher if longer courses of therapy are given. Serious systemic events have not been reported with these agents unlike other older, well-accepted antimicrobials. Rashes, while occasionally itchy and sometimes transiently unsightly, have less of an impact on a patient's daily activities than diarrhea, nausea or other more profound adverse events. However, it is essential that any rash be carefully monitored for possible, but rare, serious systemic events ensuing.

Neutrophil expression of Fas ligand and perforin directs effector CD8 T cell infiltration into antigen-challenged skin

Contact hypersensitivity (CHS) is a T cell response to hapten skin challenge of sensitized individuals proposed to be mediated by hapten-primed CD8 cytolytic T cells. Effector CD8 T cell recruitment into hapten challenge sites to elicit CHS requires prior CXCL1- and CXCL2-mediated neutrophil infiltration into the site. We investigated whether neutrophil activities directing hapten-primed CD8 T cell skin infiltration in response to 2,4-dinitro-1-fluorobenzene (DNFB) required Fas ligand (FasL) and perforin expression. Although DNFB sensitization of gld/perforin-/- mice induced hapten-specific CD8 T cells producing IFN-γ and IL-17, these T cells did not infiltrate the DNFB challenge site to elicit CHS but did infiltrate the challenge site and elicit CHS when transferred to hapten-challenged naive wild-type recipients. Hapten-primed wild-type CD8 T cells, however, did not elicit CHS when transferred to naive gld/perforin-/- recipients. Wild-type bone marrow neutrophils expressed FasL and perforin, and when transferred to sensitized gld/perforin-/- mice, they restored hapten-primed CD8 T cell infiltration into the challenge site and CHS. The FasL/perforin-mediated activity of wild-type neutrophils induced the expression of T cell chemoattractants, CCL1, CCL2, and CCL5, within the hapten-challenged skin. These results indicate FasL/perforin-independent functions of hapten-primed CD8 T cells in CHS and identify new functions for neutrophils in regulating effector CD8 T cell recruitment and immune responses in the skin.

Elevated epidermal ornithine decarboxylase activity suppresses contact hypersensitivity

Previous reports have shown that elevated polyamine biosynthesis is sufficient to promote skin tumorigenesis in susceptible mouse strains. We hypothesized that increased activity of epidermal ornithine decarboxylase (ODC), a key regulatory enzyme in polyamine biosynthesis, may suppress the cutaneous immune response in addition to stimulating proliferation. Using an ODCER transgenic mouse model in which ODC is targeted to the epidermis, we examined the effect of ODC overexpression in keratinocytes on a classic contact hypersensitivity (CHS) response. Compared with normal littermate mice, ODCER transgenic mice showed reduced ear swelling, reduced neutrophil infiltration, and decreased migration of fluorescein isothiocyanate-loaded dendritic cells (DCs) to draining lymph nodes following hapten elicitation of CHS. In addition, elevated epidermal ODC activity suppressed the levels of cytokines keratinocyte-derived chemokine, monocyte chemoattractant protein-1, interleukin-6 (IL-6), and IL-10. Adoptive transfer of lymphocytes from sensitized ODCER transgenic or normal littermate mice to naive ODCER transgenic or wild-type mice indicated that elevated epidermal ODC activity suppresses both the sensitization and elicitation phases of CHS. The specific ODC inhibitor, α-difluoromethylornithine, abrogated all suppressive effects of ODC in CHS reactions. Collectively, these data suggest that the immunosuppression promoted by increased epidermal ODC is mediated by a reduction in cytokine levels, which suppresses DC migration and reduces immune cell infiltration to the site of hapten application.

Immune hemolytic anemia associated with drug therapy

Drug-induced immune hemolytic anemia (DIIHA) is rare; it can be mild or associated with acute severe hemolytic anemia (HA) and death. About 125 drugs have been implicated as the cause. The HA can be caused by drug-independent antibodies that are indistinguishable, in vitro and in vivo, from autoantibodies causing idiopathic warm type autoimmune hemolytic anemia (AIHA). More commonly, the antibodies are drug-dependent (i.e., will only react in vitro in the presence of the drug). The most common drugs to cause DIIHA are anti-microbials (e.g., cefotetan, ceftriaxone and piperacillin), which are associated with drug-dependent antibodies. The most common drug to cause AIHA is fludarabine. Finding out which drug is causing the problem and stopping that drug is the first approach to therapy. It is not easy to identify the drug interactions accurately in vitro; laboratories specializing in this area can be of great help.

CD4+CD25+ regulatory T cells utilize FasL as a mechanism to restrict DC priming functions in cutaneous immune responses

Recent studies have suggested Fas-mediated elimination of antigen-presenting cells as an important mechanism down-regulating the induction of autoimmune responses. It remains unknown whether this mechanism restricts the magnitude of immune responses to non-self antigens. We used a mouse model of a cutaneous CD8(+) T-cell-mediated immune response (contact hypersensitivity, CHS) to test if CD4(+)CD25(+) T cells expressing FasL regulate hapten-specific effector CD8(+) T cell expansion through the elimination of Fas-expressing hapten-presenting DC. In WT mice, attenuation of CD4(+)CD25(+) T regulatory cell activity by anti-CD25 mAb increased hapten-presenting DC numbers in skin-draining LN, which led to increased effector CD8(+) T-cell priming for CHS responses. In contrast, CD4(+)CD25(+) T cells did not regulate hapten-specific CD8(+) T-cell priming and CHS responses initiated by Fas-defective (lpr) DC. Thus, restricting DC priming functions through Fas-FasL interactions is a potent mechanism employed by CD4(+)CD25(+) regulatory cells to restrict CD8(+) T-cell-mediated allergic immune responses in the skin.

Quinacrine inhibits the epidermal dendritic cell migration initiating T cell-mediated skin inflammation

Quinacrine (QC) is an anti-inflammatory drug that has been used for the treatment of malaria and rheumatoid diseases. The mechanism(s) underlying the anti-inflammatory activity of QC remains poorly understood. We recently reported the QC-mediated inhibition of the NF-kappaB pathway using an in vitro model. To test this potential mechanism in vivo, we used the contact hypersensitivity response (CHS) to chemical allergen sensitization and challenge in mice as a model of skin inflammation. The results indicated that QC treatment inhibited NF-kappaB activation in the skin during allergen sensitization. This inhibition was reflected by decreased mRNA expression and protein production of the NF-kappaB-dependent cytokines TNF-alpha and IL-1beta and the chemokine CCL21 in the skin. The decreases in these cytokines resulted in reduced migration of allergen-presenting dendritic cells from the skin into skin-draining lymph nodes and markedly decreased activation of effector CD8+ T cells for the CHS response to allergen challenge (inhibitory concentration 50% or IC50 was 55 mg/kg). These findings reveal a previously unrecognized mechanism of QC-mediated inhibition of inflammation.

Activated NKT cells increase dendritic cell migration and enhance CD8+ T cell responses in the skin

Activated NKT cells produce cytokines such as IL-4 and IFN-gamma that function locally to influence the strength and functional development of antigen-specific T cells. Here we identify an alternative mechanism by which NKT cells influence the strength of T cell responses: through modulation of peripheral dendritic cell (DC) trafficking. NKT cell activation with alpha-galactosylceramide induced high systemic levels of TNF-alpha that mediated increased DC migration from skin to draining lymph nodes. This increased DC trafficking led to a threefold increase in effector T cell priming and in the immune response elicited to antigen challenge when alpha-galactosylceramide was given at the time of immunization of the skin. These studies provide important implications for the use of NKT cell activation strategies to manipulate T cell-mediated responses including responses to cutaneous tumors and graft vs. host disease.

Low zone tolerance induced by systemic application of allergens inhibits Tc1-mediated skin inflammation

BACKGROUND

The induction of tolerance may be a promising target of strategies aimed at preventing harmful allergic diseases. Low zone tolerance (LZT), induced by epicutaneous application of low doses of contact allergens, inhibits the development of T(C)1-mediated contact hypersensitivity (CHS).

OBJECTIVE

We evaluated the effect of systemic (oral, intravenous) administration of low amounts of haptens on specific immune reactions and tolerance induction.

METHODS

By using the mouse model of LZT, we analyzed immune reactions in vivo (skin inflammation) and T-cell responses in vitro after oral, intravenous, or epicutaneous application of low amounts of the contact allergen 2,4,6-trinitro-1-chlorobenzene (TNCB).

RESULTS

Subimmunogenic doses of TNCB applied orally and intravenously induced a significant tolerance reaction in vivo comparable to epicutaneously tolerized mice, indicating that LZT is a systemically mediated tolerance reaction. In vitro analysis in all models of LZT revealed the generation of IL-10 secreting, regulatory CD4+ T cells that were absolutely required for the development of hapten-specific CD8+ T(C)2 cells. Adoptive transfer experiments identified CD8+ T(C)2 cells as effector T cells of LZT inhibiting the development of CHS-promoting T(C)1 cells and consequently the manifestation of CHS. These suppressor CD8+ T(C)2 cells were found as well in skin-draining as in mesenteric lymph nodes and in the spleen of tolerized animals independent of the route of tolerization.

CONCLUSION

These data indicate that systemic uptake and presentation of small amounts of haptens (eg, contact allergens, drugs, metals) induce the development of LZT and thus prevent inappropriate activation of the immune system and protect from allergic diseases.

CLINICAL IMPLICATIONS

These findings will be of particular importance because tolerance induction by protocols applying subimmunogenic, low amounts of haptens may be used as tools for immunotherapy in allergic and autoimmune diseases.

Adducts between nucleophilic amino acids and hexahydrophthalic anhydride, a structure inducing both types I and IV allergy

Haptens causing type I allergy have been shown to predominantly form lysine adducts in the carrier protein, while many haptens giving rise to type IV allergy preferentially form adducts with cysteine residues. Hexahydrophthalic anhydride derivatives are strong sensitizers capable of inducing allergic rhinitis, asthma and urticaria (type I allergy) and allergic contact dermatitis (type IV allergy). The ability of hexahydrophthalic anhydride (HHPA) to form adducts with nucleophilic amino acids and a model peptide in vitro is presented. Adduct formation was monitored by high-performance liquid chromatography with ultraviolet light/vis detection (LC-UV/vis) and high-performance liquid chromatography with mass spectrometric detection (LC/MS). The characterization was obtained by nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS and MS/MS). It was found that HHPA formed adducts with N(alpha)-acetylated lysine and cysteine and the non-acetylated alpha-amino group of proline and, to some extent, also with other nucleophilic amino acids. The adducts with lysine and proline were chemically stable. Addition of one HHPA to a model carrier peptide with all important nucleophilic amino acid residues showed N-terminal proline to be the major site of reaction. The addition of a second hapten gave a lysine adduct, but a minor cysteine adduct was also found. The cysteine-HHPA adducts were shown to be chemically unstable and participated in further reactions with lysine forming lysine-HHPA adducts. The results will be useful for understanding the formation of HHPA-protein adducts with the capability of being markers of exposure, and also to a deeper understanding of the chemical structures causing types I and IV allergy.

Patch testing: a retrospective analysis of 103 patients with emphasis on practical aspects for the clinician

BACKGROUND

Allergic contact dermatitis is a common dermatologic disorder caused by small chemical molecules that can penetrate the skin barrier. Thousands of chemicals capable of inducing allergic contact dermatitis have been identified. To cure allergic contact dermatitis, the allergen should be identified and eliminated from the environment of the patient. Patch testing, utilizing a variety of standard panels of the most frequent allergens, is used to identify the allergen in question. Patch testing is still the gold standard tool used to identify one or more substances that may contribute to the etiology of allergic contact dermatitis.

OBJECTIVE

To determine the frequency of patch test positivity and to identify the most common allergens in patients with suspected allergic contact dermatitis.

METHODS

A retrospective analysis of files of 103 patients who have been clinically diagnosed to have allergic contact dermatitis and have been patch tested using a standard technique with a Northern American Contact Dermatitis Group series.

RESULTS

Sixty-two patients (60.2%) showed positive reactions to one or more substance. The most common allergens were nickel sulfate, fragrance mix, and neomycin sulfate. There was an increased frequency of positive reactions to fragrance mix and a significant decrease of frequency of thimerosal positive reactions.

CONCLUSIONS

Increased awareness of allergens and their potential sources may help to limit the usage of these chemicals in manufacturing consumer products. This may have contributed to decreased prevalence rates of certain allergens such as thimerosal and paraphenylenediamine.

CD1d and CD1d-restricted iNKT-cells play a pivotal role in contact hypersensitivity

CD1d-restricted T-cells are activated by glycolipids presented by the major histocompatibility complex class-Ib molecule CD1d, found on the surface of antigen-presenting cells (APC). This interaction between APC, most notably dendritic cells (DC), and CD1d-restricted T-cells is an important regulatory step in the initiation of adaptive immune responses. It is well known that DC play a crucial role in the induction of contact hypersensitivity (CHS), a frequently studied form of in vivo T-cell-mediated immunity. In this study, we show that CD1d-restricted T-cells are also necessary for CHS, because both wild-type mice treated systemically or topically with CD1d glycolipid antagonists and CD1d-restricted T-cell-null mice have markedly diminished CHS responses. Thus, pharmacologic antagonists of CD1d can be used as effective inhibitors of CHS, a prototype for a variety of delayed-type tissue hypersensitivity responses.

Allergic contact dermatitis: pathophysiology applied to future therapy

Contact dermatitis is a common reason for patient visits to primary-care clinics and represents up to 7% of all dermatologic consultations in the US. Substantial progress has been made in elucidating the pathophysiology of contact dermatitis, particularly the allergic form. A better understanding of pathologic mechanisms has led to improved management of cases and will continue to advance treatment modalities. The present paper reviews the pathogenesis and current treatment of allergic contact dermatitis and speculates on the prospects for improved future therapy.

The intensity of neutrophil infiltration controls the number of antigen-primed CD8 T cells recruited into cutaneous antigen challenge sites

Recruitment of antigen-specific T cells into the skin is a critical initiating event during immune responses to many parasites and tumors as well as T cell-mediated, cutaneous, allergic responses and autoimmune diseases. Mechanisms directing T cell trafficking into skin remain largely undefined. Here, we show that cutaneous contact with reactive antigen induces KC/CXC chemokine ligand 1 production and neutrophil infiltration in an antigen, dose-dependent manner. The intensity of neutrophil infiltration into cutaneous antigen challenge sites, in turn, controls the number of antigen-primed T cells recruited into the site and the magnitude of the immune response elicited. The absence of responses in immune animals challenged with suboptimal doses of antigen is overcome by manipulating neutrophil infiltration that then directs antigen-primed T cell infiltration into the challenge site. This inflammation also directs T cells primed to one antigen (dinitrofluorobenzene) into the site when challenged with a completely different antigen (oxazolone). These results identify the intensity of neutrophil infiltration into cutaneous, antigen-deposition sites as a critical parameter for the level of antigen-primed T cell recruitment to mediate the adaptive immune response. This interplay between the innate and adaptive responses suggests a strategy to modulate, in a positive or negative manner, antigen-primed T cell infiltration into cutaneous inflammation sites.

CD40 Engagement Enhances Antigen-Presenting Langerhans Cell Priming of IFN-γ-Producing CD4+and CD8+T Cells Independently of IL-12

The delivery of CD40 signaling to APCs during T cell priming enhances many T cell-mediated immune responses. Although CD40 signaling up-regulates APC production of IL-12, the impact of this increased production on T cell priming is unclear. In this study an IL-12-independent T cell-mediated immune response, contact hypersensitivity (CHS), was used to further investigate the effect of CD40 ligation on the phenotypic development of Ag-specific CD4(+) and CD8(+) T cells. Normally, sensitization for CHS responses induces hapten-specific CD4(+) T cells producing type 2 cytokines and CD8(+) T cells producing IFN-gamma. Treatment of mice with agonist anti-CD40 mAb during sensitization with the hapten 2,4-dinitrofluorobenzene resulted in CHS responses of increased magnitude and duration. These augmented responses in anti-CD40 Ab-treated mice correlated with increased numbers of hapten-specific CD4(+) and CD8(+) T cells producing IFN-gamma in the skin draining lymph nodes. Identical results were observed using IL-12(-/-) mice, indicating that CD40 ligation promotes CHS responses and development of IFN-gamma-producing CD4(+) and CD8(+) T cells in the absence of IL-12. Engagement of CD40 on hapten-presenting Langerhans cells (hpLC) up-regulated the expression of both class I and class II MHC and promoted hpLC migration into the T cell priming site. These results indicate that hpLC stimulated by CD40 ligation use a mechanism distinct from increased IL-12 production to promote Ag-specific T cell development to IFN-gamma-producing cells.

CD4+ T Cells Regulate CD8+ T Cell-Mediated Cutaneous Immune Responses by Restricting Effector T Cell Development through a Fas Ligand-Dependent Mechanism

The magnitude and duration of CD8(+) T cell-mediated responses in the skin to hapten sensitization and challenge, contact hypersensitivity (CHS), is negatively regulated by CD4(+) T cells through an unknown mechanism. In this study we show that CD4(+) T cells restrict the development and expansion of hapten-specific CD8(+) T cells mediating CHS responses to 2,4-dinitrofluorobenzene. In the absence of CD4(+) T cells, high numbers of hapten-specific CD8(+) T cells producing IFN-gamma were detected in the skin-draining lymph nodes on day 5 postsensitization, and these numbers decreased slightly, but were maintained through day 9, correlating with the increased magnitude and duration of CHS responses observed in these mice. In the presence of CD4(+) T cells, the number of hapten-specific CD8(+) T cells producing IFN-gamma detected on day 5 postsensitization was lower and quickly fell to background levels by day 7. The limited development of effector CD8(+) T cells was associated with decreased numbers of hapten-presenting dendritic cells in the lymphoid priming site. This form of immunoregulation was absent after sensitization of Fas ligand-defective gld mice. Transfer of wild-type CD4(+) T cells to gld mice restored the negative regulation of CD8(+) T cell priming and the immune response to hapten challenge in gld-recipient mice. These results indicate that CD4(+) T cells restrict hapten-specific CD8(+) T cell priming for CHS responses through a Fas ligand-dependent mechanism.

Inhibition of contact hypersensitivity reaction to picryl chloride: effect of small molecular weight peptidomimetic compounds possessing inhibitory activity against metalloproteinases

We have studied the effect of small molecular weight inhibitors of snake venom metalloproteinases (SVMP) and matrix metalloproteinases (MMPs) on the induction and effector phase of the contact hypersensitivity reaction (CHR) in a mouse model. Identification of nonsteroid small molecules is very important for the development of new anti-inflammatory drugs. The compounds that we tested were synthetically modified tripeptides (peptidomimetic compounds) POL-257, POL-509, POL-443, POL-491, and POL-647, with structures based on natural occurring peptides in snake venom. A well-known hydroxamate-based inhibitor of the MMPs, Batimastat (BB-94), was also used. We have shown that these peptidomimetics possess in vitro inhibitory activity against the MMP-2 (gelatinase-A), MMP-9 (gelatinase-B), and MMP-3 (stromelysin). They also inhibit metalloproteinases purified from the venom of Crotalus adamanteus and C. atrox snakes, which are very similar to the so-called A Desintegrine, A Metalloproteinase (ADAMs) enzymes. When injected intraperitonealy before the topical application of the contact sensitizer (picryl chloride) or before the challenge, these compounds significantly inhibited the development of CHR. BB-94 at doses 0.4 and 4 mg/kg before the sensitization or before the challenge almost completely abrogated the reaction. POL-257 and POL-443 were among the most active peptidomimetics tested. They inhibited the inflammatory reaction up to 70-80%, when applied either immediately before sensitization or before challenge. POL-509, a methylated derivative of POL-257, inhibited the CHR to 40-50% when administered at either challenge or sensitization. However, when applied 24 h before the challenge, it completely abrogated the inflammatory reaction. The results show that these small molecular weight peptidomimetic compounds, as well as BB-94, are able to significantly inhibit the CHR. This finding opens possibilities for using metalloproteinase inhibitors in the treatment of allergic contact dermatitis and other inflammatory diseases.

IL-12 augments CD8+ T cell development for contact hypersensitivity responses and circumvents anti-CD154 antibody-mediated inhibition

During sensitization with dinitrofluorobenzene for contact hypersensitivity (CHS) responses, hapten-specific CD8(+) T cells develop into IFN-gamma-producing cells, and CD4(+) T cells develop into IL-4/IL-5-producing cells. Administration of IL-12 during sensitization skews CD4(+) T cell development to IFN-gamma-producing cells, resulting in exaggerated CHS responses. In the current report we tested the role of IL-12 on CD8(+) T cell development during sensitization and elicitation of CHS to dinitrofluorobenzene. Administration of IL-12 during hapten sensitization induced the expression of IL-12Rbeta2 on both CD4(+) and CD8(+) T cells, augmented IFN-gamma production by these T cell populations, and increased the magnitude and duration of the CHS response to hapten challenge. CHS responses were virtually identical in wild-type and IL-12 p40(-/-) mice. Since engagement of CD40 on APC may stimulate IL-12 production, we also tested the role of CD40-CD154 interactions on the development of IFN-gamma-producing CD4(+) and CD8(+) T cells following hapten sensitization. Development of IFN-gamma-producing CD4(+) T cells during hapten sensitization was absent in wild-type mice treated with anti-CD154 mAb or in CD154(-/-) mice. In contrast, the absence of CD40-CD154 signaling had little or no impact on the development of IFN-gamma-producing CD8(+) T cells. These results demonstrate that the development of hapten-specific Th1 effector CD4(+) T cells in CHS requires both CD40-CD154 interactions and IL-12, whereas the development of IFN-gamma-producing effector CD8(+) T cells can occur independently of these pathways.

GADD45gamma mediates the activation of the p38 and JNK MAP kinase pathways and cytokine production in effector TH1 cells

The p38 and JNK stress-activated MAPK signal transduction pathways are activated by T cell receptor (TCR) signaling and are required for IFN-gamma production by TH1 effector cells. Here, we show that the expression of GADD45gamma is induced during T cell activation and that the level of expression is higher in TH1 cells than in TH2 cells. TH1 cells from GADD45gamma(-/-) mice are severely compromised in their abilities to activate p38 and JNK in response to TCR signaling, produce much less IFN-gamma upon restimulation, and are deficient in activation-induced cell death (AICD). Additionally, GADD45gamma deficiencies caused reduced contact hypersensitivity in mice. Thus, GADD45gamma mediates activation of the p38 and JNK pathways and effector function of TH1 cells.

Overlapping roles for granulocyte-macrophage colony-stimulating factor and interleukin-3 in eosinophil homeostasis and contact hypersensitivity

Studies of mice rendered deficient in granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) have established unique roles for these cytokines in pulmonary homeostasis, resistance to infection, and antigen-specific T- and B-cell responses. In addition to these distinctive properties, however, GM-CSF and IL-3 also stimulate the development and activation of hematopoietic cells in many similar ways, raising the possibility that each factor might partially compensate for the other's absence in singly deficient mice. To test whether endogenous GM-CSF and IL-3 mediate redundant functions in vivo, we generated mice lacking both cytokines through sequential gene targeting experiments in embryonic stem (ES) cells. Surprisingly, doubly deficient animals, but not single knockouts, showed increased numbers of circulating eosinophils. Doubly deficient mice, moreover, developed weaker contact hypersensitivity reactions to haptens applied epicutaneously than mice deficient in either factor alone. Together, these findings delineate overlapping roles for GM-CSF and IL-3 in hematopoiesis and immunity. (Blood. 2001;97:922-928)

CD4+ and CD8+ T cell priming for contact hypersensitivity occurs independently of CD40-CD154 interactions

The primary effector cells of contact hypersensitivity (CHS) responses to dintrofluorobenzene (DNFB) are IFN-gamma-producing CD8(+) T cells, whereas CD4(+) T cells regulate the magnitude and duration of the response. The requirement for CD40-CD154 engagement during CD8(+) and CD4(+) T cell priming by hapten-presenting Langerhans cells (hpLC) is undefined and was tested in the current study. Similar CHS responses to DNFB were elicited in wild-type and CD154(-/-) animals. DNFB sensitization of CD154(-/-) mice primed IFN-gamma-producing CD8(+) T cells and IL-4-producing CD4(+) T cells. However, anti-CD154 mAb MR1 given during hapten sensitization inhibited hapten-specific CD8(+), but not CD4(+), T cell development and the CHS response to challenge. F(ab')(2) of MR1 failed to inhibit CD8(+) T cell development and the CHS response suggesting that the mechanism of inhibition is distinct from that of CD40-CD154 blockade. Furthermore, anti-CD154 mAb did not inhibit CD8(+) T cell development and CHS responses in mice depleted of CD4(+) T cells or in CD4(-/-) mice. During in vitro proliferation assays, hpLC from mice treated with anti-CD154 mAb during DNFB sensitization were less stimulatory for hapten-primed T cells than hpLC from either control mice or mice depleted of CD4(+) T cells before anti-CD154 mAb administration. These results demonstrate that development of IFN-gamma-producing CD8(+) T cells and the CHS response are not dependent on CD40-CD154 interactions. This study proposes a novel mechanism of anti-CD154 mAb-mediated inhibition of CD8(+) T cell development where anti-CD154 mAb acts indirectly through CD4(+) T cells to impair the ability of hpLC to prime CD8(+) T cells.

Negative regulation of CD8+ T cell function by the IFN-induced and double-stranded RNA-activated kinase PKR

The IFN-induced and dsRNA-activated kinase (PKR) mediates the antiviral and antiproliferative effects of IFN-alpha and IFN-gamma. Despite these findings, PKR:(-/-) mice have no overt immunological phenotype. Here we tested the role of PKR in cellular immunity by determining the induction and elicitation of contact hypersensitivity in PKR:(-/-) mice, a model of T cell-mediated immunity. When compared with wild type, the magnitude of contact hypersensitivity responses in PKR:(-/-) mice were 2-fold higher and of extended duration. This was also observed when naive recipients of immune CD8(+) T cells from sensitized PKR:(-/-) and CD4(+) T cells from sensitized wild-type PKR:(+/+) or PKR:(-/-) mice were challenged with hapten, indicating a regulatory defect intrinsic to the CD8(+) T cell population. Isolated lymph node T cells from PKR:(-/-) mice were hyperproliferative during Con A-mediated stimulation. These results implicate PKR for the first time in the growth control of mature T lymphocytes and give insight into the negative regulation of CD8(+) T cell-mediated immune responses.

CD4+ Th1 and CD8+ type 1 cytotoxic T cells both play a crucial role in the full development of contact hypersensitivity

The role of CD4(+) vs CD8(+) T cells in contact hypersensitivity (CHS) remains controversial. In this study, we used gene knockout (KO) mice deficient in CD4(+) or CD8(+) T cells to directly address this issue. Mice lacking either CD4(+) or CD8(+) T cells demonstrated depressed CHS responses to dinitrofluorobenzene and oxazolone compared with wild-type C57BL/6 mice. The depression of CHS was more significant in CD8 KO mice than in CD4 KO mice. Furthermore, in vivo depletion of either CD8(+) T cells from CD4 KO mice or CD4(+) T cells from CD8 KO mice virtually abolished CHS responses. Lymph node cells (LNCs) from hapten-sensitized CD4 and CD8 KO mice showed a decreased capacity for transferring CHS. In vitro depletion of either CD4(+) T cells from CD8 KO LNCs or CD8(+) T cells from CD4 KO LNCs resulted in a complete loss of CHS transfer. LNCs from CD4 and CD8 KO mice produced significant amounts of IFN-gamma, indicating that both CD4(+) and CD8(+) T cells are able to secrete IFN-gamma. LNCs from CD8, but not CD4, KO mice were able to produce IL-4 and IL-10, suggesting that IL-4 and IL-10 are mainly derived from CD4(+) T cells. Intracellular cytokine staining of LNCs confirmed that IFN-gamma-positive cells consisted of CD4(+) (Th1) and CD8(+) (type 1 cytotoxic T) T cells, whereas IL-10-positive cells were exclusively CD4(+) (Th2) T cells. Collectively, these results suggest that both CD4(+) Th1 and CD8(+) type 1 cytotoxic T cells are crucial effector cells in CHS responses to dinitrofluorobenzene and oxazolone in C57BL/6 mice.

A study of the distribution of 2,4-dinitrobenzene sensitizers between isolated lymph node cells and extracellular medium in relation to induction of contact skin sensitivity

Although induction of contact skin sensitivity by low molecular weight 2,4-dinitrobenzenes requires the formation in vivo of 2,4-dinitrophenyl-proteins, analogous protein conjugates prepared in vitro are unable to induce this hypersensitive state. Low molecular weight 2,4-dinitrobenzenes are concentrated by isolated lymph node cells, but a representative 2,4-dinitrophenyl-protein conjugate (2,4-dinitrophenyl-bovine serum albumin) was not taken up to a detectable extent by these cells. It is inferred that there exist large quantitative differences in the extent to which dinitrophenyl-proteins are localized within cells following the administration to an intact animal of (a) those simple dinitrobenzenes which are both concentrated by lymph node cells and have the capacity to form protein conjugates in vivo, and (b) 2,4-dinitrophenyl-protein conjugates prepared in vitro. It is suggested that this difference could account for the fact that a varietyof 2,4-dinitrophenyl-proteins prepared in vitro are unable to induce contact skin sensitivity.

Elicitation of allergic contact dermatitis in the guinea pig; the distribution of bound dinitrobenzene groups within the skin and quantitative determination of the extent of combination of 2,4-dinitro-chlorobenzene with epidermal protein in vivo

When one or two drops of a dilute, non-irritating solution of 2,4-dinitrochlorobenzene (DNCB) is applied to a small area of skin of the intact guinea pig, about 20 per cent of the applied material, or some derivative of it, is soon excreted in urine. In normal, as well as in specifically sensitized guinea pigs, DNCB at the site of local application becomes rapidly bound to skin protein through primary chemical bonds. Twenty-four hours after application roughly half of the material present at the local skin site is still extractable with organic solvents. Of the non-extractable dinitrophenyl groups, about 99 per cent are in epidermis, and about 85 per cent are substituted in epsilon-NH(2) groups of lysine residues. Only traces of bound dinitrophenyl groups were observed in the corium. It is uncertain whether these are formed in situ, or are experimental contaminants, or are migratory epidermally formed conjugates. Even when DNCB is injected intradermally it combines predominantly with overlying epidermis and with epidermal components of hair follicles, but only slightly with corium. The 2,4-dinitrophenyl conjugates which are localized in the deeper, viable half of the epidermis, close to the epidermal-dermal junction, are inferred to be the agents responsible for specifically evoking the allergic response in sensitized animals. Conjugates which are situated in the outer, cornified half of the epidermis are shown to be incapable of eliciting the allergic response. The results furnish a basis for interpreting a common pattern of lesions in allergic contact dermatitis as it occurs spontaneously in man.

Groalpha-mediated recruitment of neutrophils is required for elicitation of contact hypersensitivity

The factors mediating recruitment of immune T cells to challenge sites during contact hypersensitivity (CHS) responses remain unclear. To investigate the role of chemokines during elicitation of CHS, the temporal expression of chemokine genes in hapten-challenged ears was tested. KC (the murine homologoue of Groalpha) was expressed 30 min following hapten challenge in naive and hapten-sensitized mice. A rabbit KC-specific antiserum inhibited elicitation of CHS when administered to sensitized mice prior to hapten challenge. Injecting either neutrophils or immune CD8(+) T cells into the ear tissue of immune animals before hapten challenge circumvented the KC antiserum-mediated inhibition of CHS. Neutrophil depletion also inhibited CHS and was circumvented by injecting either neutrophils or hapten-primed CD8(+) T cells into ears of sensitized mice followed by specific hapten challenge. These results indicate that KC-directed neutrophil infiltration of hapten challenge sites is required for elicitation of CHS and suggest that neutrophils mediate recruitment of the hapten-specific CD8(+) T cells that subsequently produce cytokines mediating the hypersensitivity response.

The specificity of allergic reactions. I. Delayed versus Arthus hypersensitivity

Guinea pigs sensitized with either hen, duck, or goose egg albumin showed delayed hypersensitivity followed by Arthus reactions to the homologous antigen, but tended to have much weaker delayed responses and slower antibody formation to heterologous antigens. Guinea pigs with delayed hypersensitivity to one of the avian antigens had a slower antibody response to a secondary injection of heterologous antigen than to one of the homologous antigen. Sensitization with a protein conjugated with a hapten such as picryl chloride (Pi) or dinitrofluorobenzene (DFB) resulted in delayed hypersensitivity to the homologous conjugate, the homologous protein, and the homologous protein with a heterologous hapten. Circulating antibody and Arthus reactions occurred subsequently to the homologous conjugate, as well as to the homologous hapten attached to a heterologous protein. Delayed hypersensitivity thus seemed associated with the protein moiety, and Arthus responses with the hapten. Anamnestic responses followed injection of an antigen causing delayed hypersensitivity, but not of a hapten not causing delayed reactions. Thus, animals sensitized initially with Pi·HEA, DFB·HEA, or HEA produced antibodies sooner after a secondary injection of Pi·HEA than did unsensitized animals. No anamnestic response resulted when animals sensitized to Pi·BGG were injected with Pi·HEA. Thus, delayed hypersensitivity is indicated to be a preliminary and immature step in the immune process, with specificity directed against broad, more general features of the protein antigen. This intermediate step is followed by production of circulating antibody to any antigen having a similar basic structure, with the specificity of the antibody also directed against smaller immunologically active sites on the antigen molecule.

The specificity of allergic reactions. VI. Unresponsiveness to simple chemicals

"Gastric feeding" of adult guinea pigs with dinitrochlorobenzene (DCB) resulted in a specific unresponsiveness to sensitization with the specific contact hapten. The more DCB gastric-fed to a guinea pig, the more complete the unresponsiveness to the hapten. When mycobacteria were incorporated into the sensitizing emulsion, the state of unresponsiveness to the dinitrophenyl (DNP) group was less apparent. When animals gastric-fed with DCB were later sensitized with an in vitro conjugate of the hapten combined with a heterologous protein such as dinitrophenyl-hen egg albumin (DNP.HEA), an immune response similar to that in the controls occurred both to the hapten and to the protein carrier. However, when the tolerant animals were sensitized with a conjugate containing a homologous protein carrier such as dinitrophenyl guinea pig serum (DNP.GPS), they showed diminished immune responses in comparison with those in the non-tolerant controls. The presence of circulating anti-DNP antibodies from sensitization with DNP-HEA did not affect the unresponsiveness to the specific contact hapten, regardless of whether these antibodies are present before or after induction of tolerance. Sensitization with picryl chloride (PiCl) (a cross-reacting hapten), either before or after gastric feeding of DCB, did not affect the state of unresponsiveness to DNP. Similarly when the DNP-tolerant animal was sensitized with PiCl, the subsequent immune response was similar to that in the controls; cross-reactions with the DNP group both in the contact and circulating antibody phase occurred at a rate similar to that in the controls. The foregoing relationships can be explained by presuming that, upon the gastric feeding of DCB, an in vivo conjugate is formed with a somatic protein, which determines the basic specificity of the tolerance. Acquired tolerance seems to manifest an immunologic specificity similar to that of delayed hypersensitivity, a relationship not unexpected if delayed hypersensitivity is an early phase of the immune response.

Studies on the mechanism of the formation of the penicillin antigen. I. Delayed allergic cross-reactions among penicillin G and its degradation products

Seven highly purified degradation products of penicillin G (PG) were examined with regard to their ability to cross-react allergically with PG. Guinea pig allergic contact dermatitis was employed as the test system. Three of these degradation products, D-benzylpenicillenic acid (BPE), D-penicillamine, and D-α-benzylpenicilloic acid were found to cross-react with PG and also to be capable of inducing delayed contact allergy in the guinea pig. BPE and PG cross-reacted with particularly intense reactions, and other immunologic experiments indicated that PG and BPE introduce identical allergic determinant groups into epidermal proteins. These experimental results were correlated with the results of previous studies concerning the degradation pathways of PG under physiological conditions in vitro, and the chemical reactivities of these degradation products. Based on these immunologic and chemical data, a schema is proposed which suggests the chemical pathways by which PG may react with epidermal proteins in vivo to form the penicillin antigen. The identity of the specific antigenic determinant groups of the penicillin antigen is suggested. The relationship between PG allergy of the contact dermatitis type in the guinea pig and PG allergy of the immediate type in man is discussed.

The development of antibodies to penicilin in rabbits

A method for the production of antibodies specifically directed against penicillin is described. The inability of this antibody to significantly reduce the antibiotic activity of penicillin is noted. Evidence to show the variability of specificities of various sera, some directed for the most part against the side chain, others against the nucleus is presented. Studies on serum fractions separated electrophorectically indicate that the antibody migrates in the fast γ-globulin and β-globulin fractions and requires dextran or albumin to effect agglutination. The inability of penicilloic acid, an hydrolysis product of penicillin to provoke antibody formation despite its ability to inhibit the antibody is shown and the implications of this observations are discussed.

The specificity of allergic reactions. III. Contact hypersensitivity

Intradermal injection of a simple hapten (e.g., 1-fluoro-2,4-dinitrobenzene) in water-in-oil emulsion results in contact hypersensitivity to surface application of the homologous hapten and, after appearance of circulating antibody, in Arthus type hypersensitivity to a conjugate of homologous hapten with guinea pig serum. Intradermal administration of this conjugate induces delayed and subsequently Arthus hypersensitivity to the conjugate, but no evidence of a contact reaction to the hapten alone. When a conjugate of hapten plus solubilized guinea pig skin is used as the sensitizing antigen, both contact hypersensitivity to the hapten and delayed and/or Arthus reactions to the conjugate develop. These observations are consistent with the hypothesis that the specificity of contact sensitivity is directed toward some particular protein of the skin which has been modified by combination with hapten.

Glutathione metabolism in mice is enhanced more with hapten-induced allergic contact dermatitis than with irritant contact dermatitis

Cutaneous inflammation induced by electrophilic compounds involves irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD). Reduced glutathione (GSH) and related thiols have been postulated to play important roles in detoxification of electrophilic xenobiotics, protection of tissues against reactive oxygen species, and modulation of immunologic functions in normal and diseased subjects. The dynamic aspects of GSH metabolism, however, and its significance in patients with ICD and ACD remain to be clarified. The current study was carried out to elucidate the pathogenesis and possible involvement of GSH in both types of inflammation. Normal mice and mice sensitized with dinitrochlorobenzene (DNCB) were challenged by cutaneous administration of DNCB, and changes in GSH metabolism in skin and liver were determined. Kinetic analysis revealed that 24 h after challenge with DNCB, levels of hepatic glutathione and its secretion increased more markedly in the sensitized mice than in the unsensitized animals. Administration of buthionine-L-sulfoximine (BSO), a specific inhibitor of GSH synthesis, inhibited the increase in glutathione levels in the liver and the skin of both groups. Histologic examination revealed that cutaneous inflammation was enhanced by BSO more significantly in mice with ACD than with ICD. These results suggest that GSH might play an important role in the suppression of the immune reaction in mice with ACD.

Diversion of CD4+ T cell development from regulatory T helper to effector T helper cells alters the contact hypersensitivity response

Cutaneous sensitization to reactive haptens and subsequent challenge results in a T cell-mediated response, contact hypersensitivity (CHS). Recent results from this laboratory have indicated that hapten sensitization induces two populations of reactive T cells: CD8+ T cells producing interferon (IFN)-gamma which mediate the response and CD4+ T cells producing interleukin (IL)-4 and IL-10 which negatively regulate the magnitude and duration of the response. Since CD4+ T cell development to either IFN-gamma-(Th1) or IL-4/IL-10-(Th2)-producing cells is dependent upon the cytokine environment during antigen priming, we hypothesized that CD4+ T cell induction in a Th1-promoting environment would not only alter the CD4+ T cell cytokine-producing phenotype but also the course of the CHS response. Administration of the Th1-promoting cytokine IL-12 during hapten sensitization resulted in a CHS response of greater magnitude following challenge and extended the duration of the response. In hapten-sensitized mice depleted of CD8+ T cells, treatment with IL-12 induced effector CD4+ T cells. Histological examination of challenged ear tissue from these mice indicated minimal edema and an acute mononuclear cell infiltration more typical of classical delayed-type hypersensitivity than CHS. Hapten-primed CD4+ T cells from IL-12 treated, sensitized mice produced IFN-gamma, but not IL-4 in response to T cell receptor-mediated stimulation. Use of neutralizing anti-IFN-gamma antibody indicated that IL-12 not only directly promoted Th1 development but also indirectly inhibited Th2 development through stimulation of IFN-gamma production at the time of hapten sensitization. Overall, these results demonstrate that diversion of CD4+ T cell development to Th1 effector cells rather than to Th2 cells alters the efferent nature of CHS and removes a primary regulatory mechanism of the immune response.