Classical Delayed-type Hypersensitivity Research Articles

Nickel allergic contact dermatitis

The article provides basic information about nickel-associated allergic contact dermatitis (NACD). Nickel is a common metal that is commonly used in alloys for jewelry, accessories and household items. Contact with this metal often leads to the development of allergic contact dermatitis in sensitized individuals. The prevalence of NACD among the population is high: up to 19% among adults and about 10% among children and adolescents. It is noted that in female’s sensitization to nickel is observed several times more often than in males. On the risk of developing an allergic reaction to nickel, the integrity of the skin barrier, the frequency of contacts with nickel-containing household items, the presence of piercings, high humidity and hyperhidrosis are of decisive importance. Nickel ions entering the body through the alimentary route are capable of both sensitizing the body and forming tolerance to it. The pathogenesis of NACD is based on the classic delayed-type hypersensitivity reaction. The main clinical forms of this allergic dermatosis, as well as the characteristic features of the course of the disease are presented. The features of the course of NACD in patients with atopic dermatitis (AD) are analyzed in detail. The presented data clearly demonstrate that contact allergy to nickel can not only maintain, but also significantly aggravate the course of AD. The main criteria for the differential diagnosis between simple contact and allergic contact dermatitis are shown schematically. The need for early identification and termination of contact with nickel-containing household items is noted as the initial stage of NACD treatment. The main treatment for NACD is local therapy with topical glucocorticosteroids.

The Beauty of Simplicity: Delayed-Type Hypersensitivity Reaction to Measure Cellular Immune Responses in RNA-SARS-Cov-2 Vaccinated Individuals.

Background: Monitoring cellular immune responses elicited in vaccinated individuals is highly complicated. Methods: 28 individuals participated during the vaccination process with 12 BNT162b2 mRNA (Pfizer) vaccine. Specific anti-RBD IgG using a classic ELISA was performed in days 10 and 20 (after one dose of the vaccine) and on day 35 (after two vaccine doses) in serum samples of all participants. In parallel, DTH (delayed-type hypersensitivity) Skin Test using S protein was performed before (11/28) and after two doses (28/28) of the vaccine. Results: 6/28 individuals were considered positive for the specific anti-RBD IgG positive at day 10, whereas all 28 individuals were positive at day 20. Moreover, 28/28 individuals increased the OD ratios at day 36 (2 doses). DTH cutaneous test was performed on 11/28 participants at day 20 (1 dose) showing 8/11 a positive reaction at 12 h. DTH of all participants was performed on day 36 (2 doses), showing 28/28 positive reactions at 12 h. Conclusion: This report describes the first publication of the results obtained using an in vivo method, the classical DTH response to the Spike protein to assess T-cell immune responses in vaccinated individuals. This affordable and simple test would help to answer basic immunogenicity questions on large-scale population vaccine studies.

CORR Insights(®): do patients with a failed metal-on-metal hip implant with a pseudotumor present differences in their peripheral blood lymphocyte subpopulations?

T he study by Catelas and colleagues adds to the current scientific consensus that adaptive immune responses to metals occurs in a subset of all people with metal implants. The study authors also found that the incidence of pseudotumors correlates with systemic evidence of metal-related delayed-type hypersensitivity (DTH) responses and elevated metal ion levels. The current study identifies alterations in circulating adaptive immune cells in people with elevated levels of metal debris and pseudotumors. These findings support past histological and T-cell function studies, indicating pseudotumors are more prevalent in people with DTH-type immune reactivity. This highlights the growing recognition of these phenomena as central to implant performance in some individuals/implant designs. Case and group studies [4, 5] indicate that once locally activated, adaptive immune inflammation to metal contributes to (if not, mediates) the pathogenesis of poor implant performance. Metal DTH reactivity is a lymphocyte mediated response, similar to a Type IV DTH reaction. Metal-on-metal (MoM) hip failures have been associated with classic DTH responses including periimplant activated lymphocyte accumulations (aseptic lymphocytic vasculitisassociated lesions, [ALVAL]), and dermal and functional lymphocyte hypersensitivity responses to metals [2, 7, 11]. Elevated metal exposure can also cause different forms of toxicity responses in tissue, bone, and immune cells, including cobalt-induced hypoxia-like responses, postulated as causing pseudotumors [10]. Lymphocyte reactivity (metal DTH responses/ALVAL) and pseudotumors can be caused separately [6, 8]. Currently, there are no accepted thresholds for systemic metal ion levels that necessarily indicate for pseudotumor formation or immune reactions [1, 7]; it remains an increased risk association. This CORR Insights is a commentary on the article ‘‘Do Patients With a Failed Metal-onmetal Hip Implant With a Pseudotumor Present Differences in Their Peripheral Blood Lymphocyte Subpopulations?’’ by Catelas and colleagues available at: DOI: 10.1007/ s11999-015-4466-8. The author certifies that she, or any members of her immediate family, has no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writers and do not reflect the opinion or policy of CORR or The Association of Bone and Joint Surgeons. This CORR Insights comment refers to the article available at DOI: 10.1007/s11999015-4466-8. N. J. Hallab PhD (&) Department of Orthopedic Surgery, Rush University Medical Center, 1735 W Harrison, Cohn Research Bldg, #722, Chicago, IL 60612, USA e-mail: nhallab@rush.edu CORR Insights Published online: 13 October 2015 The Association of Bone and Joint Surgeons1 2015

Multi-Scale Optical Imaging of the Delayed Type Hypersensitivity Reaction Attenuated by Rapamycin

Neutrophils and monocytes/macrophages (MMs) play important roles in the development of cell-mediated delayed type hypersensitivity (DTH). However, the dynamics of neutrophils and MMs during the DTH reaction and how the immunosuppressant rapamycin modulates their behavior in vivo are rarely reported. Here, we take advantage of multi-scale optical imaging techniques and a footpad DTH reaction model to non-invasively investigate the dynamic behavior and properties of immune cells from the whole field of the footpad to the cellular level. During the classic elicitation phase of the DTH reaction, both neutrophils and MMs obviously accumulated at inflammatory foci at 24 h post-challenge. Rapamycin treatment resulted in advanced neutrophil recruitment and vascular hyperpermeability at an early stage (4 h), the reduced accumulation of neutrophils (> 50% inhibition ratio) at 48 h, and the delayed involvement of MMs in inflammatory foci. The motility parameters of immune cells in the rapamycin-treated reaction at 4 h post-challenge displayed similar mean velocities, arrest durations, mean displacements, and confinements as the classic DTH reaction at 24 h. These results indicate that rapamycin treatment shortened the initial preparation stage of the DTH reaction and attenuated its intensity, which may be due to the involvement of T helper type 2 cells or regulatory T cells.

Establishment and characterization of a sustained delayed-type hypersensitivity model with arthritic manifestations in C57BL/6J mice

IntroductionRheumatoid arthritis (RA) is a chronic progressive, inflammatory and destructive autoimmune disease, characterised by synovial joint inflammation and bone erosion. To better understand the pathophysiology and underlying immune mechanisms of RA various models of arthritis have been developed in different inbred strains of mice. Establishment of arthritis models with components of adaptive immunity in the C57BL/6J strain of mice has been difficult, and since most genetically modified mice are commonly bred on this background, there is a need to explore new ways of obtaining robust models of arthritis in this strain. This study was undertaken to establish and characterise a novel murine model of arthritis, the delayed-type hypersensitivity (DTH)-arthritis model, and evaluate whether disease can be treated with compounds currently used in the treatment of RA.MethodsDTH-arthritis was induced by eliciting a classical DTH reaction in one paw with methylated bovine serum albumin (mBSA), with the modification that a cocktail of type II collagen monoclonal antibodies was administered between the immunisation and challenge steps. Involved cell subsets and inflammatory mediators were analysed, and tissue sections evaluated histopathologically. Disease was treated prophylactically and therapeutically with compounds used in the treatment of RA.ResultsWe demonstrate that DTH-arthritis could be induced in C57BL/6 mice with paw swelling lasting for at least 28 days and that disease induction was dependent on CD4+ cells. We show that macrophages and neutrophils were heavily involved in the observed pathology and that a clear profile of inflammatory mediators associated with these cell subsets was induced locally. In addition, inflammatory markers were observed systemically. Furthermore, we demonstrate that disease could be both prevented and treated.ConclusionsOur findings indicate that DTH-arthritis shares features with both collagen-induced arthritis (CIA) and human RA. DTH-arthritis is dependent on CD4+ cells for induction and can be successfully treated with TNFα-blocking biologics and dexamethasone. On the basis of our findings we believe that the DTH-arthritis model could hold potential in the preclinical screening of novel drugs targeting RA. The model is highly reproducible and has a high incidence rate with synchronised onset and progression, which strengthens its potential.

A Microbial Glycolipid Functions as a New Class of Target Antigen for Delayed-type Hypersensitivity

Delayed-type hypersensitivity (DTH) is marked by high levels of protein antigen-specific T cell responses in sensitized individuals. Recent evidence has revealed a distinct pathway for T cell immunity directed against glycolipid antigens, but DTH to this class of antigen has been undetermined and difficult to prove due to their insolubility in aqueous solutions. Here, glucose monomycolate (GMM), a highly hydrophobic glycolipid of the cell wall of mycobacteria, was dispersed in aqueous solutions in the form of octaarginine-modified liposomes and tested for its ability to elicit cutaneous DTH responses in bacillus Calmette-Guerin (BCG)-immunized guinea pigs. After an intradermal challenge with the GMM liposome, a significant skin induration was observed in BCG-immunized, but not mock-treated, animals. The skin reaction peaked at around 2 days with local infiltration by mononuclear cells, and therefore, the response shared basic features with the classical DTH to protein antigens. Lymph node T cells from BCG-immunized guinea pigs specifically increased IFN-γ transcription in response to the GMM liposome, and this response was completely blocked by antibodies to CD1 lipid antigen-presenting molecules. Finally, whereas the T cells increased transcription of both T helper (Th) 1-type (IFN-γ and TNF-α) and Th2-type (IL-5 and IL-10) cytokines in response to the purified protein derivative or tuberculin, their GMM-specific response was skewed to Th1-type cytokine production known to be critical for protection against tuberculosis. Thus, our study reveals a novel form of DTH with medical implications.

Induction of delayed-type hypersensitivity and interferon-gamma to Candida albicans and anti-hen-egg white lysozyme antibody as phenotypic markers of enhanced bovine immune response

Delayed-type hypersensitivity (DTH) is a protective localized cell-mediated immune response (CMIR), primarily against intracellular pathogens. DTH is widely used in research to assess immune responsiveness and has been a valuable diagnostic test in commercial settings. In pigs and other species both antibody (AMIR) and CMIR have been considered as reliable phenotypic markers of selection programs for disease resistance. Therefore in cattle, it was also considered important to find antigen/adjuvant combinations capable of inducing AMIR and CMIR without interfering with diagnostic tests. The objectives of the present study were to evaluate the combined use of hen-egg white lysozyme (HEWL) and Candida albicans adjuvanted with Quil A in lactacting Holstein cows for the induction of anti-HEWL antibody, as well as DTH and IFN-γ to C. albicans as phenotypic markers of enhanced immune responsiveness. Thirty one lactating Holstein cows were immunized with HEWL to induce antibody responses and C. albicans to sensitize for DTH. Two test antigens, candin and C. albicans whole cell (CaWC), were used to induce the effector phase of DTH. PBS was used as the negative control. In addition, two different skin sites (neck versus tail) were tested to evaluate differences in skin site responsiveness. C. albicans-induced IFN-γ production, as an indicator of a type 1 response, was evaluated by ELISA. Microscopic evaluation of skin samples at DTH sites was performed in five randomly selected cows and these skin biopsies were scored based on inflammation and cell infiltration. Results demonstrated the presence of classical DTH response to C. albicans, in that DTH responses peaked at 24 h post-intradermal injections and cell infiltration was composed largely of mononuclear leukocytes, typical of DTH skin reactions in cattle. The only difference in test antigens was that DTH to candin showed a higher early response (6 h) than CaWC and a rapid decrease in inflammation from 24 to 48 h. The neck was significantly more sensitive than the tail skin-fold as a DTH test site. IFN-γ was detected on days 14 and 21 post-immunization in plasma from blood incubated with candin. Significant primary and secondary anti-HEWL antibodies were also detected, indicating that this combination of test antigens could be used as phenotypic markers of immune responsiveness in cattle.

Trehalose Dimycolate Elicits Eosinophilic Skin Hypersensitivity in Mycobacteria-Infected Guinea Pigs

Delayed-type hypersensitivity represents high levels of protein Ag-specific adaptive immunity induced by mycobacterial infection, and can be monitored in the Ag-challenged skin. Besides protein Ags, recent evidence has suggested that a substantial immunity directed against glycolipid Ags is also elicited in response to mycobacterial infection, but skin hypersensitivity to this class of Ags has not been fully assessed. To address this issue directly, glycolipid-specific skin reactions were evaluated in guinea pigs infected with Mycobacterium avium complex (MAC). Significant skin induration was observed in MAC-infected, but not mock-infected, guinea pigs, following intradermal administration of a mixture of MAC-derived glycolipids. Surprisingly, this glycolipid-specific skin response involved up-regulated expression of IL-5 mRNA in situ and marked local infiltration of eosinophils. Challenge experiments with individual glycolipid components detected an outstanding capability for trehalose dimycolate (TDM), but not a structurally related glycolipid, glucose monomycolate, to elicit the skin response. T lymphocytes derived from the spleen of MAC-infected, but not uninfected, guinea pigs specifically responded to TDM in vitro by up-regulating IL-5 transcription, and this response was not blocked by Abs that reacted to the known guinea pig group 1 CD1 proteins. Finally, the eosinophilic skin hypersensitivity to TDM was also elicited in guinea pigs vaccinated with bacillus Calmette-Guerin, which contrasted sharply with the classical delayed-type hypersensitivity response to the purified protein derivative. Therefore, the TDM-elicited eosinophilic response defines a new form of hypersensitivity in mycobacterial infection, which may account for local infiltration of eosinophils often observed at the site of infection.

Divergent in vitro and in vivo correlates of HIV-specific T-cell responses during onset of HIV viraemia

Cellular immune responses to HIV-1 have been examined mainly in peripheral blood mononuclear cells (PBMC). During onset of HIV replication and antigenaemia after discontinuation of highly active antiretroviral therapy (HAART), PBMC may theoretically contain HIV-specific T cells that are qualitatively and quantitatively different from specific T cells dominating in the tissues. PBMC responses throughout HIV immunotherapy trials may therefore be skewed during recurrent viraemia. To compare cellular HIV-specific in vitro responses in PBMC during onset of HIV viraemia with corresponding in vivo responses, represented by classical delayed-type hypersensitivity tests (DTH). HIV patients (n = 38), pre-immunized with four HIV-1 p24-like consensus peptides (Vacc-4x) during HAART, were subjected to a 14-week treatment interruption with recurrent HIV viraemia. Proliferative T-cell responses to Vacc-4x p24 peptides, HIV p24 protein, and cytomegalovirus (CMV) proteins were measured in PBMC. Corresponding Vacc-4x peptide DTH were expressed as skin infiltrate areas after 48 h. After 14 weeks without HAART, HIV-1 RNA increased to 72,500 copies/ml (median). The Vacc-4x p24 peptide- and HIV-1 p24 protein-induced T-cell proliferation concurrently decreased by 81 and 93% in PBMC during viraemia (medians, P < or = 0.03), whereas proliferative responses to CMV antigens were stable. In contrast, the Vacc-4x DTH areas, rather tended to increase by 36% (P = 0.08) and contained infiltrates dominated by proliferating T cells and macrophages. Divergent in vitro and in vivo HIV-specific cellular immune responses were found during recurrent HIV viraemia. The clinical relevance of both surrogate markers for HIV-related immune responses should be compared in future studies.

Gene expression in the elicitation phase of guinea pig DTH and CHS reactions.

Delayed-type hypersensitivity (DTH) reactions are divided into classical DTH induced by protein antigens and contact hypersensitivity (CHS) induced by haptens. It has been reported that different cytokines and T cell subsets are involved in the induction of each DTH reaction. We previously isolated many genes whose expression is elevated during elicitation of skin DTH reaction in guinea pigs. In this study, we focused on the expression of tryptophanyl-tRNA synthetase (WRS), ferritin heavy chain and major histocompatibility complex (MHC) class II genes to investigate the different regulatory mechanisms in classical DTH and CHS. Furthermore, the expression of various cytokines and chemokines was examined. WRS expression in classical DTH was higher than that in CHS, and the expression of interferon-gamma but not that of transforming growth factor-beta showed similar patterns. MHC class II mRNA increased only in classical DTH. The differential expression of WRS and MHC class II genes in classical DTH might be caused by the differential expression of interferon-gamma and/or the involvement of CD4(+) T cells in classical DTH, respectively. In contrast, the expression of ferritin heavy chain and interleukin-1beta was elevated in CHS, and also by treatment with dinitrochlorobenzene in unsensitized guinea pigs, and expression of both was correlated.

Effects of tumor necrosis factor alpha on dendritic cell accumulation in lymph nodes draining the immunization site and the impact on the anticryptococcal cell-mediated immune response.

Cell-mediated immune (CMI) responses and tumor necrosis factor alpha (TNF-alpha) have been shown to be essential in acquired protection against Cryptococcus neoformans. Induction of a protective anticryptococcal CMI response includes increases in dendritic cells (DC) and activated CD4(+) T cells in draining lymph nodes (DLN). During the expression phase, activated CD4(+) T cells accumulate at a peripheral site where cryptococcal antigen is injected, resulting in a classical delayed-type hypersensitivity (DTH) reaction. Induction of a nonprotective anticryptococcal CMI response results in no significant increases in the numbers of DC or activated CD4(+) T cells in DLN. This study focuses on examining the role of TNF-alpha in induction of protective and nonprotective anticryptococcal CMI responses. We found that neutralization of TNF-alpha at the time of immunization with the protective immunogen (i) reduces the numbers of Langerhans cells, myeloid and lymphoid DC, and activated CD4(+) T cells in DLN and (ii) diminishes the total numbers of cells, the numbers of activated CD4(+) T cells, and amount of gamma interferon at the DTH reaction site. Although TNF-alpha neutralization during induction of the nonprotective CMI response had little effect on cellular and cytokine parameters measured, it did cause a reduction in footpad swelling when mice received challenge in the footpad. Our findings show that TNF-alpha functions during induction of the protective CMI response by influencing the accumulation of all three DC subsets into DLN. Without antigen stimulated DC in DLN, activated CD4(+) T cells are not induced and thus not available for the expression phase of the CMI response.

Differences in components at delayed-type hypersensitivity reaction sites in mice immunized with either a protective or a nonprotective immunogen of Cryptococcus neoformans.

Cell-mediated immunity is the major protective mechanism against Cryptococcus neoformans. Delayed swelling reactions, i.e., delayed-type hypersensitivity (DTH), in response to an intradermal injection of specific antigen are used as a means of detecting a cell-mediated immune (CMI) response to the antigen. We have found previously that the presence of an anticryptococcal DTH response in mice is not always indicative of protection against a cryptococcal infection. Using one immunogen that induces a protective anticryptococcal CMI response and one that induces a nonprotective response, we have shown that mice immunized with the protective immunogen undergo a classical DTH response characterized by mononuclear cell and neutrophil infiltrates and the presence of gamma interferon and NO. In contrast, immunization with the nonprotective immunogen results in an influx of primarily neutrophils and production of tumor necrosis factor alpha (TNF-alpha) at the DTH reaction site. Even when the anticryptococcal DTH response was augmented by blocking the down-regulator, CTLA-4 (CD152), on T cells in the mice given the nonprotective immunogen, the main leukocyte population infiltrating the DTH reaction site is the neutrophil. Although TNF-alpha is increased at the DTH reaction site in mice immunized with the nonprotective immunogen, it is unlikely that TNF-alpha activates the neutrophils, because the density of TNF receptors on the neutrophils is reduced below control levels. Uncoupling of DTH reactivity and protection has been demonstrated in other infectious-disease models; however, the mechanisms differ from our model. These findings stress the importance of defining the cascade of events occurring in response to various immunogens and establishing the relationships between protection and DTH reactions.

Mechanisms involved in the immunotoxicity induced by dermal application of JP-8 jet fuel.

Dermal application of JP-8 jet fuel induces immune suppression. Classic delayed-type hypersensitivity as well as the induction of contact hypersensitivity to allergens applied to the shaved skin of JP-8-treated mice is suppressed. In addition, the ability of T cells isolated from JP-8-treated mice to proliferate in vitro is suppressed. Here we focused on further characterizing the immunotoxicity induced by JP-8 exposure and determining the mechanism involved. Suppression of T-cell proliferation was first noted 3 to 4 days after a single JP-8 treatment and lasted for approximately 3 weeks, at which time T-cell proliferation returned to normal. Cellular immune reactions appear to be more susceptible to the immunosuppressive effects of JP-8, as antibody production in JP-8-treated mice was identical to that found in normal controls. The mechanism through which dermal application of JP-8 suppresses cell-mediated immune reactions appears to be via the release of immune biological-response modifiers. Blocking the production of prostaglandin E(2) with a selective cyclooxygenase-2 inhibitor abrogated JP-8-induced immune suppression. Neutralizing the activity of interleukin-10 with a highly specific monoclonal antibody also blocked JP-8-induced immune suppression. Furthermore, injecting JP-8-treated mice with recombinant interleukin-12, a cytokine that drives cell-mediated immune reactions in vivo, overcame the immunotoxic effects of JP-8 and restored immune function. These data indicate that immune suppressive cytokines, presumably produced by JP-8-treated epidermal cells, are responsible for immune suppression in JP-8-treated mice and that blocking and/or neutralizing their production in vivo overcomes the immunotoxic effects of JP-8.

Chemical Activation of Innate and Specific Immunity in Contact Dermatitis

Recent reports have suggested that chemical-induced allergic contact dermatitis may not be a traditional type IV hypersensitivity, in part due to the dual irritant and antigenic properties of sensitizing chemicals. In order to investigate the contribution of these properties to the molecular and cellular mechanism underlying allergic contact dermatitis, we evaluated oxazolone-induced changes in cell populations and cytokine production in the dermis of transgenic mice with impaired innate immunity (the FcgammaR subunit knockout mouse), and absent specific immunity (the athymic mouse), and the appropriate B6,129F2 and C57BL/6 control mice. Oxazolone and croton oil were applied in a single sensitizing dose, or in sensitizing and challenge doses, and the dermal response was evaluated by immunohistochemistry. In the wild type mice, with or without sensitization to oxazolone or croton oil, we observed mixed Th1/Th2 cytokine production and both CD4+ and CD8+ T lymphocytes; however, the neutrophil was the predominant cell in the dermis, even 72 h after final chemical application. Athymic mice displayed a similar neutrophil response with moderate Th1/Th2 cytokine production, and FcgammaR subunit knockout mice exhibited very mild dermatitis when treated with either oxazolone or croton oil. These results provide support for the hypothesis that allergic contact dermatitis is not a classic delayed type hypersensitivity, demonstrate the importance of the interaction between the irritant and antigenic properties of sensitizing chemicals in the development of allergic contact dermatitis, and suggest that the irritant effect of chemicals may be mediated through the cutaneous innate immune system.

Dermal application of JP-8 jet fuel induces immune suppression.

Chronic exposure to JP-8 jet fuel induces lung toxicity, adverse neurological effects and some liver and kidney dysfunction. In addition, inhalation of JP-8 induces immune suppression. Besides the lung, the other major route of JP-8 exposure is via the skin. In this study we tested the hypothesis that dermal exposure to JP-8 is immune suppressive. JP-8 was applied to the skin of adult female C3H/HeN mice and various immune parameters were examined. Dermal exposure to JP-8, either multiple small exposures (50 microl for 5 days) or a single large dose (250-300 microl) resulted in immune suppression. The induction of contact hypersensitivity was impaired in a dose-dependent manner regardless of whether the contact allergen was applied directly to the JP-8-treated skin or at a distant un-treated site. In addition, the generation of a classic delayed-type hypersensitivity reaction to a bacterial antigen (Borellia burgdorferi) injected into the subcutaneous space was suppressed by dermal application of JP-8 at a distant site. The ability of splenic T lymphocytes from JP-8-treated mice to proliferate in response to plate-bound monoclonal anti-CD3 was also significantly suppressed. Interleukin-10, a cytokine with potent immune suppressive activity, was found in the serum of JP-8-treated mice, suggesting that the mechanism of systemic immune suppression may involve the upregulation of cytokine release by JP-8. These findings confirm the immunosuppressive effects of JP-8 and demonstrate that dermal exposure to JP-8 is immunotoxic.

Dendritic cells in allergy.

Dendritic cells in allergy.

Type 2 Immune Deviation Has Differential Effects on Alloreactive CD4+ and CD8+ T Cells

Allograft rejection has been associated with detection of the type 1 lymphokines, IFN-gamma and IL-2. The role of type 2 cytokines (IL-4 and IL-5) remains controversial, as is whether alloreactive CD4+ and CD8+ T cells behave similarly when exposed to type 2 cytokine-enhancing manipulations. We studied the characteristics of alloreactive CD4+ and CD8+ T cells before and after type 2 immune deviation induced by IL-4 plus anti-IFN-gamma Ab. Alloreactive T cells from naive mice were low in frequency, produced only IL-2, and were predominantly CD4+, while alloreactive T cells from allograft-primed mice were high in frequency, produced IFN-gamma, IL-2, and IL-4, and were predominantly CD8+. Type 2 immune deviation of allospecific CD4+ T cells resulted in IL-4 and IL-5 production without IFN-gamma, consistent with unipolar type 2 immunity. These T cells mediated delayed-type hypersensitivity, but not cytotoxicity. Under identical type 2 cytokine-inducing conditions, allospecific CD8+ T cells were primed to become IL-4, IL-5, and IFN-gamma producers, and exhibited cytotoxicity, but not classic delayed-type hypersensitivity. Adoptive transfer of either cell population into SCID recipients of allogeneic skin resulted in graft rejection, with stable allospecific type 2 cytokine production in vivo. Adoptive transfer of the IL-4/IL-5-producing CD4+ T cells, but not the CD8+ T cells, induced a distinct histopathology characterized by marked eosinophilic infiltration of the skin. We conclude that type 2 immune deviation has differential effects on CD4+ and CD8+ T cells and results in emergence of alternate effector mechanisms capable of destroying allografts.

The role of dendritic cells in contact hypersensitivity

Contact hypersensitivity (CHS) is a hapten-specific skin inflammation mediated by T cells that recognize haptenated peptides presented by major histocompatibility complex (MHC) class I and class II molecules on antigen-presenting cells (APCs). CHS is a self-limited inflammation of short duration which peaks at 24 hours after challenge. CHS spontaneously resolves in a few days, suggesting the existence of potent downregulatory mechanisms which control and/or block the effector cells of contact sensitivity (CS).In a recent Review article on the pathophysiology of CHS, Stephan Grabbe and Thomas Schwarz stressed the differences between CHS and classical delayed-type hypersensitivity (DTH) reactions to proteins [1xGrabbe, S. and Schwarz, T. Immunol. Today. 1998; 19: 37–44Abstract | Full Text PDF | PubMed | Scopus (413)See all References[1]. Whereas DTH responses are mediated by CD4+ effector cells, it has been reported that the CHS inflammatory reaction is mediated by CD8+ effector cells and that CD4+ T cells are endowed with downregulatory properties [2xBour, H., Peyron, E., Gaucherand, M. et al. Eur. J. Immunol. 1995; 25: 3006–3010Crossref | PubMedSee all References, 3xXu, H., Diiulio, N.A., and Fairchild, R.L. J. Exp. Med. 1996; 183: 1001–1012Crossref | PubMedSee all References]. These observations raised the question of the nature of the APCs responsible for priming the hapten-specific CD4+ and CD8+ T cells. Although epidermal dendritic cells (DCs) (Langerhans cells; LCs) have been shown to induce effector cells of CHS, it was hypothesized that they were not responsible for the priming of downregulatory CD4+ cells, instead a special type of APC, lacking appropriate costimulatory signals, could be involved in the phenomenon [1xGrabbe, S. and Schwarz, T. Immunol. Today. 1998; 19: 37–44Abstract | Full Text PDF | PubMed | Scopus (413)See all References[1].We recently addressed the question of the nature of the APC responsible for the priming of downregulatory T cells, in the murine model of CHS induced by treatment with the contact allergen 2,4-dinitrofluorobenzene (DNFB) in which CD8+ cells are effector cells of CS and CD4+ cells behave as downregulatory cells [2xBour, H., Peyron, E., Gaucherand, M. et al. Eur. J. Immunol. 1995; 25: 3006–3010Crossref | PubMedSee all References[2]. Mature DCs were either generated from the skin after overnight culture in granulocyte–macrophage colony-stimulating factor (GM-CSF) or generated in vitro from bone marrow progenitors of wild-type C57BL/6 as well as of β2-microglobulin-deficient (β2-m−/−) and Aβ−/− mice, which are genetically deficient in MHC class I or MHC class II molecules, respectively. These DCs, expressing a mature DC phenotype (CD11c+, DEC-205+, B7-1+, B7-2+, CD40+ and MHC class IIhi), were haptenated in vitro and injected into naive C57BL/6 wild-type recipients which five days later received a cutaneous application of DNFB on the ears. These experiments demonstrated that MHC class I molecules on DCs were mandatory for the induction of CHS reaction inasmuch as DCs recovered from wild-type C57BL/6 [class I+/class II+ (I+/II+)] and Aβ−/− (I+/II−) mice, but not from β2-m−/− (I−/II+), could prime for CHS (Ref. [4xKrasteva, M., Kehren, J., Horand, F. et al. J. Immunol. 1998; 160: 1181–1190PubMedSee all References[4]). Although II+/I− DCs could not sensitize for CS they could prime for hapten-specific CD4+ T cells in the lymphoid organs. More importantly, haptenated II+/I− DCs could induce a down-regulation of CS reaction when injected in wild-type C57BL/6 recipient mice at the time of cutaneous sensitization. Thus, the same type of APC, i.e. mature DCs, which have the remarkable property of presenting exogenous antigens on both MHC class I and MHC class II molecules [5xShen, Z.H., Reznikoff, G., Dranoff, G., and Rock, K.L. J. Immunol. 1997; 158: 2723–2730PubMedSee all References[5], can simultaneously and independently prime for MHC class I-restricted effectors and MHC class II-restricted downregulatory T cells [4xKrasteva, M., Kehren, J., Horand, F. et al. J. Immunol. 1998; 160: 1181–1190PubMedSee all References[4]. It is most likely that skin LCs are involved in processing of haptens bound on self or exogenous proteins into peptides associated to MHC class I and MHC class II molecules [6xLepoittevin, J.P. and Leblond, I. Eur. J. Dermatol. 1997; 7: 151–154See all References[6]and that upon migration to the draining lymph nodes they become efficient in activation of both CD4+ and CD8+ T hapten-specific precursors. Finally, these data suggest that targeting haptens on MHC class II molecules on epidermal DCs could be used to induce antigen-specific tolerance in CHS.

Sequential T cell response involved in tumor rejection of sarcoma, Meth A, in syngeneic mice.

We investigated the type of T cell response involved in Meth A tumor rejection in primary immune and hyperimmune syngeneic mice. It was found that a CD4+ T cell‐mediated delayed‐type hypersensitivity (DTH) response activating non‐specific killer cells such as macrophages, NK and LAK cells, without a specific CD8+ cytotoxic T lymphocyte (CTL) response, was the major immune response leading to Meth A tumor rejection in primary immune mice. In contrast, the specific CD8+ CTL response was the major response leading to the tumor rejection, in addition to CD4+ T cell‐mediated DTH response, in hyperimmune mice. Analysis of CD4+ T cell clones established from primary immune and hyperimmune spleen cells indicated that a CD4+ T cell clone (C9) of primary immune mice (although only one clone was established) was of Th1 type, and induced cytotoxicity in accessory cells by classic DTH in vitro. Eight CD4+ T cell clones were established from hyperimmune spleen cells. Six out of the eight clones were of the Th2 type and two were Th0‐like. However, no Th1‐type CD4+ T cell clone was established from hyperimmune spleen cells. All of these CD4+ T cell clones, even the Th2‐type clones, were capable of inducing cytotoxicity in vitro in T cell‐depleted accessory cells, as in an in vitro DTH response. We postulate on the basis of these results that the T cell response leading to Meth A tumor rejection in vivo sequentially changed from a CD4+ T cell‐mediated classic DTH response to a CD8+ CTL response, in addition to a cellular response mediated probably by Th2‐type cells, during the process of repeated immunization.

Allergic and Immunologic Skin Disorders

The skin represents a unique immunologic organ poised to protect the host from invading organisms and environmental antigens. The skin is also an important target for a variety of allergic and autoimmune responses. Mast cells are key to the pathogenesis of urticaria, angioedema, and mastocytosis. Atopic dermatitis is the consequence of an immunoregulatory abnormality resulting in a skin-directed T helper type 2 response. Allergic contact dermatitis is an example of classic delayed type hypersensitivity. Circulating autoantibodies against the epidermis are a key mechanism by which bullous skin diseases occur.