Therapeutic potential of lipids obtained from γ-irradiated PBMCs in dendritic cell-mediated skin inflammation

BACKGROUND

Since numerous pathological conditions are evoked by unwanted dendritic cell (DC) activity, therapeutic agents modulating DC functions are of great medical interest. In regenerative medicine, cellular secretomes have gained increasing attention and valuable immunomodulatory properties have been attributed to the secretome of γ-irradiated peripheral blood mononuclear cells (PBMCs). Potential effects of the PBMC secretome (PBMCsec) on key DC functions have not been elucidated so far.

METHODS

We used a hapten-mediated murine model of contact hypersensitivity (CH) to study the effects of PBMCsec on DCs in vivo. Effects of PBMCsec on human DCs were investigated in monocyte-derived DCs (MoDC) and ex vivo skin cultures. DCs were phenotypically characterised by transcriptomics analyses and flow cytometry. DC function was evaluated by cytokine secretion, antigen uptake, PBMC proliferation and T-cell priming.

FINDINGS

PBMCsec significantly alleviated tissue inflammation and cellular infiltration in hapten-sensitized mice. We found that PBMCsec abrogated differentiation of MoDCs, indicated by lower expression of classical DC markers CD1a, CD11c and MHC class II molecules. Furthermore, PBMCsec reduced DC maturation, antigen uptake, lipopolysaccharides-induced cytokine secretion, and DC-mediated immune cell proliferation. Moreover, MoDCs differentiated with PBMCsec displayed diminished ability to prime naïve CD4+T-cells into TH1 and TH2 cells. Furthermore, PBMCsec modulated the phenotype of DCs present in the skin in situ. Mechanistically, we identified lipids as the main biomolecule accountable for the observed immunomodulatory effects.

INTERPRETATION

Together, our data describe DC-modulatory actions of lipids secreted by stressed PBMCs and suggest PBMCsec as a therapeutic option for treatment of DC-mediated inflammatory skin conditions.

FUNDING

This research project was supported by the Austrian Research Promotion Agency (Vienna, Austria; grant "APOSEC" 862068; 2015-2019) and the Vienna Business Agency (Vienna, Austria; grant "APOSEC to clinic" 2343727).

Epidermal NLRP10 contributes to contact hypersensitivity responses in mice

The nucleotide binding and oligomerization domain-like receptor (NLR) protein NLRP10 is highly expressed in the epidermis and contributes to cell-autonomous responses against invasive bacteria. To investigate the role of NLRP10 in inflammatory responses of the skin we analyzed the effect of full-body and keratinocyte-specific depletion of NLRP10 in croton oil-induced irritant contact dermatitis (ICD) and 1-fluoro-2,4-dinitrobenzene (DNFB)-induced contact hypersensitivity (CHS) in mice. Nlrp10(-/-) mice were phenotypically normal and skin repair after wounding was not affected by lack of NLRP10. Similarly, we did not detect a contribution of NLRP10 to the ICD response induced by croton oil. In contrast, Nlrp10(-/-) mice showed significantly reduced inflammation in the DNFB-induced CHS response as compared to control animals. Microscopic analysis revealed significantly reduced numbers of CD4(+) and CD8(+) T cells in the infiltrates of animals lacking NLRP10 expression after CHS challenge. Epidermis-specific deletion of Nlrp10 by keratin-14 promotor driven Cre-recombinase was sufficient to account for this phenotype, although lymphocyte recruitment seemed to be unaltered in animals lacking NLRP10 expression in keratinocytes. Taken together, we provide evidence that NLRP10 contributes to T-cell-mediated inflammatory responses in the skin and highlight a physiological role of NLRP10 in epidermal keratinocytes.

[Study on the immunocompetence of polysaccharide extracted from root of Salvia miltiorrhiza]

OBJECTIVE

To study the immune activity of polysaccharide extracted from root of Salvia miltiorrhiza.

METHODS

Investigated the effects of polysaccharide extracted from root of Salvia miltiorrhiza on lymphocyte proliferation response of mouse induced by LPS (the lipopolysaccharide LPS), phagocytosis of the peritoneal macrophage of mice to chick erythrocytes and the mouse models of delayed type hypersensitivity (DTH) response induced by DNFB.

RESULTS

Lymphocyte proliferation and phagocytosis of the peritoneal macrophage of mice could be promoted by the polysaccharide, which could inhibit ear edema and capillary permeability increase induced by DNFB and enlarged the thymus and splenic index in mice. The expression of iNOS, IFN-alpha and IL-1beta was inhibited significantly in the treatment group.

CONCLUSION

The polysaccharide extracted from Salvia miltiorrhiza can improve immune function.

Amphiregulin is not essential for induction of contact hypersensitivity

BACKGROUND

Amphiregulin (AR) is expressed in Th2 cells, rather than Th1 cells, and plays an important role in Th2 cell/cytokine-mediated host defense against nematodes. We also found earlier that AR mRNA expression was strongly upregulated in inflamed tissue during Th2 cell/cytokine-mediated fluorescein isothiocyanate (FITC)-induced contact hypersensitivity (CHS), suggesting a contribution of AR to the induction of those responses.

METHODS

To elucidate the role of AR in the induction of FITC- or dinitrofluorobenzene (DNFB)-induced CHS, AR-deficient mice were sensitized and/or challenged with FITC or DNFB epicutaneously. The levels of FITC-mediated skin dendritic cell (DC) migration and FITC-specific lymph node cell proliferation and cytokine production were assessed by flow cytometry, [3H]-thymidine incorporation and ELISA, respectively, after FITC sensitization. The degree of ear swelling, the activities of myeloperoxidase (MPO) and eosinophil peroxidase (EPO) in inflammatory sites and the levels of FITC-specific immunoglobulin (Ig) in sera were determined by histological analysis, colorimetric assay and ELISA, respectively, after FITC challenge.

RESULTS

DC migration and FITC-specific lymph node cell proliferation and cytokine production were normal in the AR-deficient mice. Ear swelling, tissue MPO and EPO activities and FITC-specific serum Ig levels were also similar in AR-deficient and -sufficient mice.

CONCLUSIONS

Amphiregulin is not essential for the induction of FITC- or DNFB-induced CHS responses in mice.

Enhanced contact hypersensitivity by delayed T-helper 2 response in BALB/c mice

T-helper (Th) 1/Th2 balance determines the direction of contact hypersensitivity (CHS). To clarify the immunopathogenesis of contact dermatitis, 2,4-dinitrofluorobenzene (DNFB)-induced CHS reaction was compared between the BALB/c and C57BL/6 mice. The two strains were sensitized with DNFB systemically and challenged with DNFB locally. The CHS reaction in BALB/c mice was intense compared with that in C57BL/6 mice at 24 and 48 hours post-DNFB challenge. The dermal lesions were characterized by infiltration of lymphocytes, eosinophils, neutrophils, and macrophages including CD4+ and CD8+ T cells, and interleukin (IL)-4-producing(+) and interferon (IFN)-gamma+ cells in BALB/c mice. In C57BL/6 mice, the composition of inflammatory cells was same as those in BALB/c mice except for eosinophils, CD4+ T cells, and IL-4+ cells. There was no increase in the number of mast cells in the two strains. Local and systemic productions of IL-4 and IFN-gamma in BALB/c mice were higher than those in C57BL/6 mice. Although blood IgE values increased in BALB/c mice, but not in C57BL/6 mice, at 48 hours postchallenge, its value was low. The delayed Th2-like response together with Th1-like response in BALB/c mice may induce strong CHS reaction compared with C57BL/6 mice, which may dominantly develop Th1-like reaction. Moreover, mast cell and IgE do not appear to be involved in delayed CHS.

Neutralizing anti-IL-10 antibody blocks the protective effect of tapeworm infection in a murine model of chemically induced colitis

There is increasing evidence that parasitic helminth infection has the ability to ameliorate other disease conditions. In this study the ability of the rat tapeworm, Hymenolepis diminuta, to modulate dinitrobenzene sulfonic acid (DNBS)-induced colitis in mice is assessed. Mice receiving DNBS (3 mg intrarectally) developed colitis by 72 h after treatment. Mice infected 8 days before DNBS with five H. diminuta larvae were significantly protected from the colitis, as gauged by reduced clinical disease, histological damage scores, and myeloperoxidase levels. This anticolitic effect was dependent on a viable infection and helminth rejection, because no benefit was observed in mice given killed larvae or in infected STAT6 knockout mice or rats, neither of which eliminate H. diminuta. The anticolitic effect of H. diminuta was associated with increased colonic IL-10 mRNA and stimulated splenocytes from H. diminuta- plus DNBS-treated mice produced more IL-10 than splenocytes from DNBS-only treated mice. Coadministration of an anti-IL-10 Ab blocked the anticolitic effect of prophylactic H. diminuta infection. Also, mice infected 48 h after DNBS treatment showed an enhanced recovery response. Finally, using a model of OVA hypersensitivity, we found no evidence of concomitant H. diminuta infection enhancing enteric responsiveness to subsequent ex vivo OVA challenge. The data show that a viable infection of H. diminuta in a nonpermissive system exerts a profound anticolitic effect (both prophylactically and as a treatment) that is mediated at least in part via IL-10 and does not predispose to enhanced sensitivity to bystander proteins.

Effector CD8+T cells are suppressed by measles virus infection during delayed type hypersensitivity reaction

Measles virus infection reduces or abolishes delayed type hypersensitivity reactions (DTH) in humans. We have previously shown that the primary 2,4-dinitrofluorobenzene (DNFB) response is temporarily suppressed by measles virus in cotton rats. Here, we demonstrate that also the secondary DNFB response (cutaneous hypersensitivity [CHS]) is suppressed in cotton rats by measles virus infection. As in mice, DNFB specific CD8 T cells are the predominant T cell response in cotton rats. After MV infection, CD8 T cells are reduced in their proliferative capacity whereas the CD4/CD8 ratio, the number and activation status of CD8 T cells is not affected. As a result of impaired proliferation of DNFB specific T cells the DTH response (measured as ear swelling) is reduced in measles virus infected cotton rats. At the same time as DNFB specific T cell responses are suppressed, spontaneous proliferation of lymphocytes as evidence for immune activation is found.

Src homology 2 domain-containing protein tyrosine phosphatase substrate 1 regulates the migration of Langerhans cells from the epidermis to draining lymph nodes

Src homology 2 domain-containing protein tyrosine phosphatase substrate 1 (SHPS-1) is a member of the signal regulatory protein family in which the extracellular region interacts with its ligand, CD47. Recent studies have demonstrated that SHPS-1 plays an important role in cell migration and cell adhesion. We demonstrate in this study, using immunohistochemical and flow cytometric analyses, that murine Langerhans cells (LCs) express SHPS-1. Treatment of mice ears with 2,4-dinitro-1-fluorobenzene significantly reduced the number of epidermal LCs, and that reduction could be reversed by pretreatment with mAb to SHPS-1 or the CD47-Fc fusion protein. Treatment with the SHPS-1 mAb in vivo reduced the number of FITC-bearing cells in the lesional lymph nodes after the application of FITC to the skin. The SHPS-1 mAb inhibited the in vivo TNF-alpha-induced migration of LCs. The emigration of dendritic cells expressing I-A(b+) from skin explants to the medium was also reduced by the SHPS-1 mAb. We further demonstrate that the chemotaxis of a murine dendritic cell line, XS52, by macrophage inflammatory protein-3beta was significantly inhibited by treatment with the SHPS-1 mAb or CD47-Fc recombinant protein. Finally, we show that migration of LCs was attenuated in mutant mice that lack the intracellular domain of SHPS-1. These observations show that the ligation of SHPS-1 with the SHPS-1 mAb or with CD47-Fc abrogates the migration of LCs in vivo and in vitro, which suggests that the SHPS-1-CD47 interaction may negatively regulate LC migration.

Ultraviolet radiation-induced regulatory T cells not only inhibit the induction but can suppress the effector phase of contact hypersensitivity

Epicutaneous application of haptens to UV-exposed skin induces hapten-specific tolerance. This is mediated via regulatory T cells (Tr), as i.v. injection of T cells from UV-tolerized mice into naive animals renders the recipients unresponsive to the respective hapten. However, when UV-induced Tr are injected i.v. into sensitized mice, contact hypersensitivity (CHS) is not suppressed, suggesting that Tr inhibit the induction, but not the elicitation, of CHS and are inferior to T effector cells. As sensitization takes place in the lymph nodes, but elicitation occurs in the area of challenge, we postulated that Tr injected i.v. locate to the lymph nodes and not to the periphery and therefore only suppress the induction, not the elicitation, of CHS. Indeed, i.v. injection of Tr into sensitized mice did not inhibit CHS, although injection of Tr into the ears of sensitized mice suppressed the challenge. Inhibition was hapten specific, as injection of dinitrofluorobenzene (DNFB)-specific Tr into the ears of oxazolone (OXA)-sensitized mice did not affect challenge with OXA. However, when ears of OXA-sensitized mice were injected with DNFB-specific Tr and painted with DNFB before OXA challenge, CHS was suppressed. Inhibition correlated with the local expression of IL-10. Depletion studies and FACS analysis revealed that Tr express the lymph node-homing receptor L-selectin, but not the ligands for the skin-homing receptors E- and P-selectin, suggesting that UV-induced Tr, although able to inhibit T effector cells, do not suppress the elicitation of CHS upon i.v. injection, because they obviously do not migrate into the skin.

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.

Neuronal repellent Slit2 inhibits dendritic cell migration and the development of immune responses

One of the essential functions of dendritic cells is to take up Ags in peripheral tissues and migrate into secondary lymphoid organs to present Ags to lymphocytes for the induction of immune responses. Although many studies have demonstrated that the migration of dendritic cells is closely associated with the development of immune responses, little is known about factors that inhibit dendritic cell migration and control the extent of immune responses to Ag stimulation. We show that Slit2, a neuronal repellent factor, is up-regulated in the skin by allergen sensitization and down-regulates the migration of Langerhans cells. The effect is mediated by direct interaction of Slit2 with cells that express a Slit-specific receptor, Robo1. Slit2-mediated inhibition of Langerhans cell migration results in suppression of contact hypersensitivity responses. These findings provide insights into a novel mechanism by which Slit2 functions as an anti-inflammatory factor for the initiation of immune responses.

Cutting Edge: Vasoactive Intestinal Peptide Acts as a Potent Suppressor of Inflammation In Vivo byTrans-Deactivating Chemokine Receptors

Chemokines mediate trafficking of leukocytes to sites of inflammation and immune responses through activation of G protein-coupled receptors, which thereby provide appealing targets for novel anti-inflammatory agents. Vasoactive intestinal peptide (VIP) is an immunosuppressive neurotransmitter. We show that VIP inhibited the function of chemokine receptors on monocytes and CD4(+) T lymphocytes, with impaired chemotaxis and calcium flux in response to the cognate chemokine ligands CXCL12, CCL3, CCL4, and CCL5. This was mediated by VIP receptor type 1 and was not caused by chemokine receptor internalization. However, VIP caused dose-dependent phosphorylation of the chemokine receptor CCR5. This trans-deactivation process was studied in a murine model of delayed-type hypersensitivity: continuous infusion of VIP resulted in significant abrogation of monocyte and lymphocyte infiltration. Circulating mononuclear cells from VIP-infused mice were unable to respond to chemokines. VIP may provide a novel approach to treatment of inflammatory diseases through inhibition of chemokine-dependent leukocyte recruitment.

Innate CD4+CD25+ regulatory T cells are required for oral tolerance and inhibition of CD8+ T cells mediating skin inflammation

To elucidate the role of CD4+CD25+ regulatory T cells in oral tolerance, we used the model of contact hypersensitivity (CHS) to 2,4-dinitrofluorobenzene (DNFB), which is mediated by CD8+ Tc1 effector cells independently of CD4+ T-cell help. Conversely to normal mice, invariant chain knock-out (KO) (Ii degrees / degrees ) mice, which are deficient in CD4+ T cells, cannot be orally tolerized and develop a chronic hapten-specific CHS response. Transfer of naive CD4+ T cells before hapten gavage into Ii degrees / degrees mice restores oral tolerance by a mechanism independent of interleukin-10 (IL-10) production by CD4+ T cells. That naturally occurring CD4+CD25+ T cells are critical for oral tolerance induction is demonstrated by the finding that (1) transfer of CD4+CD25+ but not CD4+CD25- T cells into Ii degrees / degrees recipients completely prevents the CHS response and skin infiltration by CD8+ T cells, by blocking development of hapten-specific CD8+ T cells; (2) in vivo depletion of CD4+CD25+ cells by antibody treatment in normal mice impairs oral tolerance; and (3) CD4+CD25+ T cells inhibit hapten-specific CD8+ T-cell proliferation and interferon gamma (IFN gamma) production, in vitro. These data show that naturally occurring CD4+CD25+ T cells are instrumental for orally induced tolerance and are key actors for the control of antigen-specific CD8+ T-cell effectors mediating skin inflammation.

Psychological Stress Exerts an Adjuvant Effect on Skin Dendritic Cell Functions In Vivo

Psychological stress affects the pathophysiology of infectious, inflammatory, and autoimmune diseases. However, the mechanisms by which stress could modulate immune responses in vivo are poorly understood. In this study, we report that application of a psychological stress before immunization exerts an adjuvant effect on dendritic cell (DC), resulting in increased primary and memory Ag-specific T cell immune responses. Acute stress dramatically enhanced the skin delayed-type hypersensitivity reaction to haptens, which is mediated by CD8(+) CTLs. This effect was due to increased migration of skin DCs, resulting in augmented CD8(+) T cell priming in draining lymph nodes and enhanced recruitment of CD8(+) T cell effectors in the skin upon challenge. This adjuvant effect of stress was mediated by norepinephrine (NE), but not corticosteroids, as demonstrated by normalization of the skin delayed-type hypersensitivity reaction and DC migratory properties following selective depletion of NE. These results suggest that release of NE by sympathetic nerve termini during a psychological stress exerts an adjuvant effect on DC by promoting enhanced migration to lymph nodes, resulting in increased Ag-specific T cell responses. Our findings may open new ways in the treatment of inflammatory diseases, e.g., psoriasis, allergic contact dermatitis, and atopic dermatitis.

Involvement of Dectin-2 in Ultraviolet Radiation-Induced Tolerance

Hapten sensitization through UV-exposed skin induces hapten-specific tolerance which can be adoptively transferred by injecting T cells into naive recipients. The exact phenotype of the regulatory T cells responsible for inhibiting the immune response and their mode of action remain largely unclear. Dectin-2 is a C-type lectin receptor expressed on APCs. It was postulated that dectin-2 interacts with its putative ligands on T cells and that the interaction may deliver costimulatory signals in naive T cells. Using a soluble fusion protein of dectin-2 (sDec2) which should inhibit this interaction, we studied the effect on contact hypersensitivity (CHS) and its modulation by UV radiation. Injection of sDec2 affected neither the induction nor the elicitation phase of CHS. In contrast, UV-induced inhibition of the CHS induction was prevented upon injection of sDec2. In addition, hapten-specific tolerance did not develop. Even more importantly, injection of sDec2 into tolerized mice rendered the recipients susceptible to the specific hapten, indicating that sDec2 can break established tolerance. FACS analysis of spleen and lymph node cells revealed a significantly increased portion of sDec2-binding T cells in UV-tolerized mice. Furthermore, transfer of UV-mediated suppression was lost upon depletion of the sDec2-positive T cells. Taken together, these data indicate that dectin-2 and its yet unidentified ligand may play a crucial role in the mediation of UV-induced immunosuppression. Moreover, sDec2-reactive T cells appear to represent the regulatory T cells responsible for mediating UV-induced tolerance.

IL-18 binding protein protects against contact hypersensitivity

Allergic contact dermatitis, the clinical manifestation of contact hypersensitivity, is one of the most common disorders of the skin. It is elicited upon multiple cutaneous re-exposure of sensitized individuals to the sensitizing agent. In this study, we demonstrate that using IL-18 binding protein (IL-18BP) to neutralize IL-18 significantly reduced clinical symptoms in a murine model of contact hypersensitivity. Furthermore, IL-18BP alleviated the relapses during established disease, as indicated by significant protection during re-exposure of mice that had previously undergone a contact hypersensitivity response without treatment. Although edema was not influenced, IL-18BP reduced the number of T cells homing to sites of inflammation, resulting in diminished local production of IFN-gamma. Thus, by preventing the accumulation of effector T cells to the target tissue, IL-18BP appears to be a potent protective mediator to counter skin inflammation during contact hypersensitivity. Taken together with the evidence that IL-18 is present in tissue samples of the human disease, our data reinforces IL-18BP as a candidate for this therapeutic indication.

Differential regulation of sensitizer-induced inflammation and immunity by acute restraint stress in allergic contact dermatitis

Previously, we demonstrated that restraint stress applied before chemical sensitization modulates allergic contact dermatitis (ACD) differently than restraint applied before challenge. In this study, we asked if these dichotomous restraint-induced changes reflect modulation of the cutaneous microenvironment or changes in development of antigen-specific immunity in the lymph node (LN) of BALB/c mice. Our data confirm that restraint suppresses T cell-dependent immunity in ACD when applied prior to sensitization or prior to challenge and demonstrate that the stress-induced increase in ear swelling is due to heightened inflammation associated with ACD and is dependent upon the sensitization status of the mouse.

Assessment of glycosylation-dependent cell adhesion molecule 1 as a correlate of allergen-stimulated lymph node activation

Early changes in gene expression have been identified by cDNA microarray technology. Analysis of draining auricular lymph node tissue sampled at 48 h following exposure to the potent contact allergen 2,4-dinitrofluorobenzene (DNFB) provided examples of up- and down-regulated genes, including onzin and guanylate binding protein 2, and glycosylation-dependent cell adhesion molecule 1 (GlyCAM-1), respectively. Allergen-induced changes in these three genes were confirmed in dose-response and kinetic analyses using Northern blotting and/or reverse transcription-polymerase chain reaction techniques. The results confirmed that these genes are robust and relatively sensitive markers of early changes provoked in the lymph node by contact allergen. Upon further investigation, it was found that altered expression of the adhesion molecule GlyCAM-1 was not restricted to treatment with DNFB. Topical sensitization of mice to a chemically unrelated contact allergen, oxazolone, was also associated with a decrease in the expression of mRNA for GlyCAM-1. Supplementary experiments revealed that changes in expression of this gene are independent of the stimulation by chemical allergens of proliferative responses by draining lymph node cells. Taken together these data indicate that the expression of GlyCAM-1 is down-regulated rapidly following epicutaneous treatment of mice with chemical allergens, but that this reduction is associated primarily with changes in lymph node cell number, or some other aspect of lymph node activation, rather than proliferation.

IL-13 is necessary, not simply sufficient, for epicutaneously induced Th2 responses to soluble protein antigen

Th2 responses are clearly involved in the pathogenesis of atopic disease. Thus, understanding the factors responsible for Th2 sensitization at sites of allergen exposure, such as airway and skin, is crucial for directing therapeutic or preventive strategies. Contrary to other models of Th2 sensitization to proteins, we have reported that Th2 responses induced by epicutaneous exposure to OVA are IL-4 independent. Combined deficiency of both IL-4 and IL-13 signaling did prevent Th2 generation, suggesting that IL-13 was mediating these IL-4-independent responses. It was not clear, however, whether IL-13 was simply replacing the need for IL-4 in genetically deficient mice or if IL-13 played a unique role. In the present study, we show that Th2 responses induced by epicutaneous OVA exposure (including lung inflammatory responses after inhaled Ag challenge, OVA-specific IgG1, and draining lymph node IL-5 production) are impaired in IL-13-deficient (IL-13(-/-)) mice compared with wild type. In contrast, i.p. sensitization of IL-13(-/-) mice resulted in responses equivalent to wild type. Generation of contact hypersensitivity to dinitrofluorobenzene, which involves Th1 and CD8(+) effector cells, was also intact in IL-13(-/-) mice. Taken together, the data indicate that IL-13 is the major inducer of Th2 generation in the cutaneous microenvironment, being required independently of IL-4. This fact, in combination with the known abundance of IL-13 in atopic dermatitis skin lesions, emphasizes the potentially important role of the skin as a site for Th2 sensitization to environmental allergens, particularly in atopic individuals.

Hepatic leukocyte recruitment in a model of acute colitis

There is a close relationship between inflammatory bowel disease (IBD) and various hepatobiliary disorders. The objective of this study was to determine whether hepatic leukocyte recruitment occurs in experimental colitis. We used the murine model of colitis induced by 2,4-dinitrobenezenesulfonic acid (DNBS). Male C57Bl/6 mice received an intrarectal injection of 4 mg DNBS in 100 microl 50% ethanol. Controls received 100 microl 50% ethanol. The hepatic microcirculation was examined at 3 and 14 days post-DNBS by intravital video microscopy. Three days post-DNBS, when mice had developed acute colitis, there was associated hepatic leukocyte recruitment. Within the postsinusoidal venules there was a fourfold increase in the flux of rolling leukocytes that was P-selectin dependent but not alpha(4)-integrin dependent. There was also an increase in stationary leukocytes within the sinusoids, although this was not associated with an increase in serum alanine transaminase. By 14 days post-DNBS when macroscopic evidence of colonic inflammation was resolved, rolling within the postsinusoidal venules had returned to control levels. In this murine model of colitis, we describe a link between acute colonic inflammation and remote hepatic leukocyte recruitment that is P-selectin dependent. Active IBD may lead to remote hepatic inflammation.

Effect of the dose and composition of an autologous hapten-modified melanoma vaccine on the development of delayed-type hypersensitivity responses

We have reported that treatment of melanoma patients with a vaccine consisting of autologous tumor cells modified with the hapten, dinitrophenyl (DNP) and preceded by low-dose cyclophosphamide induces delayed-type hypersensitivity (DTH) to autologous, unmodified tumor cells and that this response is a significant predictor of survival. We analyzed the vaccines prepared for 284 patients who were treated following resection of regional or distant metastases to find out whether the dose and composition determined the immunological response. A positive DTH response (> or =5 mm induration) to unmodified autologous tumor cells was induced in 57% of the patients (median: 5 mm; range: 0-22 mm). Regression analysis showed no significant association between the magnitude of DTH and the number of live (trypan blue exclusion) melanoma cells per dose over a dosage range of 0.5-25.0 x 10(6). Surprisingly, there was a small but significant positive relationship between the mean number of dead cells in the vaccines of a given patient and that patient's maximum DTH to unmodified melanoma cells. Only 37% of patients whose vaccines contained >50% live cells developed DTH, as compared with 69% and 65% of patients whose vaccines contained 26% to 50% or < or =25% live cells, respectively. Thus, it appears that dead tumor cells contribute to the immunogenicity of the DNP vaccine, but other factors such as the administration schedule may be more important determinants of immunological and clinical outcome.

Chymase participates in chronic dermatitis by inducing eosinophil infiltration

An epicutaneous application of 2,4-dinitrofluorobenzene (DNFB) to a mouse ear caused a transient skin swelling, and the repetition of the challenge enlarged the contact dermatitis. The repeated challenge with DNFB also induced eosinophil infiltration on the application site. Administration of a chymase inhibitor significantly inhibited the ear swelling as well as eosinophil accumulation. An intradermal injection of human chymase to the mouse ear also elicited transient skin swelling and eosinophil infiltration, both of which were augmented in proportion to the number of injections. Human serum albumin and heat-inactivated chymase failed to induce such skin reactions, suggesting the participation of proteolytic activity of the enzyme. In addition, chymase stimulated eosinophil migration in vitro in a concentration-dependent manner. Taken together, these observations suggest that mast cell chymase may contribute to development of the DNFB-induced dermatitis, probably by promoting eosinophil infiltration. It is therefore possible that chymase plays a role in pathogenesis of chronic dermatitis such as atopic dermatitis.

Mast cell-derived TNF-alpha primes sensory nerve endings in a pulmonary hypersensitivity reaction

TNF-alpha is a cytokine associated with inflammatory diseases, including asthma. Increased levels of TNF-alpha were found in the bronchoalveolar lavage fluid of mice undergoing a dinitrofluorobenzene (DNFB)-induced non-IgE-mediated pulmonary hypersensitivity reaction. We report in this work that TNF-alpha increases the susceptibility of sensory neurons to dinitrobenzene sulfonic acid (DNS) and capsaicin, leading to a tracheal vascular hyperpermeability response in DNFB-sensitized and DNS-challenged mice. mAb against TNF-alpha or the TNFR1 inhibited this hyperpermeability response in DNFB-sensitized and DNS-challenged mice. Furthermore, the hyperpermeability response after DNS challenge was abolished in DNFB-sensitized mast cell-deficient WBB6F(1)-W/W(V) mice. These animals showed a remarked decrease of TNF-alpha bronchoalveolar lavage fluid levels after a single DNS challenge. The hyperpermeability response after DNS challenge was regained in mast cell-deficient mice after mast cell reconstitution. These findings indicate a prominent role for TNF-alpha and its TNFR1 in the DNFB-induced tracheal hyperpermeability response. We propose that a priming effect of mast cell-derived TNF-alpha on the sensory neurons could be the mechanism of action of TNF-alpha in the vascular hyperpermeability response in tracheas of mice undergoing a pulmonary hypersensitivity reaction.

Hypersensitivity reactions in mouse airways after a single and a repeated hapten challenge

OBJECTIVE AND DESIGN

In this study, we examined the effect of a single and a repeated hapten-challenge on inflammatory processes in the airways of mice undergoing a hapten-induced non-IgE mediated hypersensitivity reaction.

METHODS

BALB/c mice were skin-sensitized with the hapten dinitroflourobenzene (DNFB) and intra-airway challenged with dinitrobenzene sulphonic acid (DNS). Mucosal exudation, tracheal vascular permeability, cellular accumulation, and serum murine mast cell protease (MMCP) were investigated at different time points after the first DNS-challenge and 30 min after a repeated DNS-challenge.

RESULTS

MMCP levels in serum were increased at all time points after single challenge and repeated challenge. Increased vascular permeability as determined by Monastral blue staining, was found in the trachea of DNFB-sensitized mice after single DNS-challenge. A second exposure to DNS profoundly enhanced the Monastral blue labeling of the tracheal blood vessels of DNFB-sensitized mice. Furthermore, increased mucosal exudation and polymorphonuclear cell (PMN) accumulation were present in DNFB-sensitized mice compared to vehicle-sensitized animals after the first DNS challenge.

CONCLUSIONS

Increased mucosal exudation, vascular permeability, and PMN accumulation are prominent inflammatory features of the DNFB-induced hypersensitivity reaction in the airways. Furthermore, mast cell activation is associated with this hapten-induced hypersensitivity reaction.

Carcinogen-induced inflammation and immunosuppression are enhanced in xeroderma pigmentosum group A model mice associated with hyperproduction of prostaglandin E2

Xeroderma pigmentosum group A (XPA) gene-deficient mice easily developed skin cancers by the application of topical chemical carcinogens as well as by UV irradiation. As certain chemical carcinogens have been shown to be immunosuppressive, we examined the inflammatory and immunosuppressive effects of dimethylbenz(a)anthracene (DMBA) on XPA mice. Compared with wild-type mice, XPA mice showed greater ear swelling and reduction of epidermal Langerhans cells after DMBA application. Topical application of DMBA impaired the induction of contact hypersensitivity, initiated either locally or at distant sites. These DMBA-induced local and systemic immunosuppressions were more greatly enhanced in XPA mice than in wild-type mice. DMBA application induced pronounced production of PGE(2), IL-10, and TNF-alpha in the skin of XPA mice. Treatment with indomethacin, a potent inhibitor of PG biosynthesis, inhibited DMBA-induced inflammation and local immunosuppression. In XPA mice, increased serum IL-10 was detected after DMBA treatment. Excess production of PGE(2), TNF-alpha, and IL-10 after DMBA application may be involved in the enhanced local and systemic immunosuppression in DMBA-treated XPA mice. Susceptibility to DMBA-induced skin tumors in XPA mice may be due to easy impairment of the immune system by DMBA in addition to a defect in the repair of DMBA-DNA adduct. Enhanced immunosuppression by chemical carcinogens as well as the mutagenicity of these mutagens might be associated with the high incidence of internal malignancies seen in XP patients. Moreover, these results supported the hypothesis that persistent DNA damage is a trigger for the production of immunoregulatory cytokines.

Involvement of substance P and central opioid receptors in morphine modulation of the CHS response

Morphine administration prior to challenge with the antigen 2,4-dinitro-fluorobenzene increases the contact hypersensitivity (CHS) response in rats. The present study extended these findings by showing that central, but not systemic, administration of N-methylnaltrexone antagonized the morphine-induced enhancement of the CHS response. The importance of the neuroimmune mediator substance P was shown via the attenuation of the morphine-induced enhancement following both systemic and topical administration of the NK-1 antagonist WIN51,708. Taken together, the findings of the present study provide new data showing that central opioid receptors and peripheral substance P are involved in the morphine-induced enhancement of the CHS response.

Functional caspase-1 is required for Langerhans cell migration and optimal contact sensitization in mice

Langerhans cell (LC) migration from epidermis to draining lymph node is a critical first step in cutaneous immune responses. Both TNF-alpha and IL-1 beta are important signals governing this process, but the potential regulatory role of IL-1 alpha processing by caspase-1 is unknown. In wild-type (WT) mice, application of the contact allergens 2,4-dinitrofluorobenzine and oxazolone lead to a marked reduction in epidermal LC numbers, but in caspase-1-deficient mice this reduction was not observed. Moreover, although intradermal injection of TNF-alpha (50 ng) induced epidermal LC migration in WT mice, this cytokine failed to induce LC migration in caspase-1-deficient mice. Intradermal IL-1 beta (50 ng) caused a similar reduction in epidermal LC numbers in both WT and caspase-1-deficient mice, indicating that, given an appropriate signal, caspase-1-deficient epidermal LC are capable of migration. Contact hypersensitivity to both 2,4-dinitrofluorobenzine and oxazolone was inhibited in caspase-1-deficient mice, indicating a functional consequence of the LC migration defect. In organ culture the caspase-1 inhibitor Ac-YVAD-cmk, but not control peptide, potently inhibited the epidermal LC migration that occurs in this system, and reduced spontaneous migration of LC was observed in skin derived from caspase-1-deficient mice. Moreover, Ac-YVAD-cmk applied to BALB/c mouse skin before application of contact sensitizers inhibited LC migration and contact hypersensitivity in vivo. Taken together, these data indicate that caspase-1 may play a central role in the regulation of LC migration and suggest that the activity of this enzyme is amenable to control by specific inhibitors both in vivo and in vitro.

The determination of draining lymph node cell cytokine mRNA levels in BALB/c mice following dermal sodium lauryl sulfate, dinitrofluorobenzene, and toluene diisocyanate exposure

Differential modulation has been demonstrated in interleukin-4 (IL-4), IL-10, and interferon gamma (IFN-gamma) mRNA and protein secretion patterns of cells isolated from the draining lymph nodes of mice following exposure to T cell and respiratory sensitizers. Using a multiprobe ribonuclease protection assay, the following investigation examined the mRNA expression patterns of multiple cytokines associated with respiratory sensitization for modulation following exposure to chemicals known primarily to induce irritation (sodium lauryl sulfate), respiratory sensitization (toluene diisocyanate), or T cell-mediated hypersensitivity (dinitrofluorobenzene) responses. On days 0 and +5 female BALB/c mice were exposed to either test article or vehicle on the shaven dorsal lumbar region; on days +10 through +12 the mice received test article on the dorsal aspect of each ear. On day +13 animals were euthanized, draining lymph nodes were excised, and mRNA was isolated immediately or following 24 or 48 h of culture in the presence or absence of concanavalin (Con) A. Differential expression of cytokine mRNA was most notable following 24 h incubation with Con A. Modulation of IL-4, -10, and IFN-gamma following chemical exposure was consistent with previous studies. In addition, IL-9, -13, and -15 were significantly elevated only following toluene diisocyanate exposure. Further investigations of these cytokines may provide additional insight into the mechanisms of chemically induced respiratory sensitization and provide endpoints for the detection of a chemical's ability to elicit IgE-mediated hypersensitivity responses.

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.

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.

Differential production of prostaglandin E(2) in male and female mice subjected to thermal injury contributes to the gender difference in immune function: possible role for 15-hydroxyprostaglandin dehydrogenase

We have previously reported a macrophage-mediated gender difference in postburn immunosuppression, which was dependent upon elevated levels of circulating 17beta-estradiol (E(2)) and, in part, interleukin-6. Herein we examined the role of prostaglandin E(2) (PGE(2)), a potent suppressor of cell-mediated immunity. Circulating levels of PGE(2) were significantly elevated in females but not males at 10 days postburn (P < 0.01), and indomethacin treatment fully restored the delayed-type hypersensitivity and splenocyte proliferative responses of thermally injured females. While there was no difference in cyclooxygenase-2 protein expression in the lungs and liver of thermally injured male and female mice, there was a marked decrease in the protein expression of 15-hydroxyprostaglandin dehydrogenase in females. These data demonstrate that PGE(2) is a critical mediator of immunosuppression in thermally injured female mice and that the increase in circulating PGE(2) is derived, in part, from decreased degradation and clearance of PGE(2).

Inhibition of functional T cell priming and contact hypersensitivity responses by treatment with anti-secondary lymphoid chemokine antibody during hapten sensitization

Recent studies have suggested a pivotal role for secondary lymphoid chemokine (SLC) in directing dendritic cell trafficking from peripheral to lymphoid tissues. As an extension of these studies, we examined the consequences of anti-SLC Ab treatment during Ag priming on T cell function in an inflammatory response. We used a model of T cell-mediated inflammation, contact hypersensitivity (CHS), where priming of the effector T cells is dependent upon epidermal dendritic cell, Langerhans cells, and migration from the hapten sensitization site in the skin to draining lymph nodes. A single injection of anti-SLC Ab given at the time of sensitization with FITC inhibited Langerhans cell migration into draining lymph nodes for at least 3 days. The CHS response to hapten challenge was inhibited by anti-SLC Ab treatment in a dose-dependent manner. Despite the inhibition of CHS, T cells producing IFN-gamma following in vitro stimulation with anti-CD3 mAb or with hapten-labeled cells were present in the skin-draining lymph nodes of mice treated with anti-SLC Ab during hapten sensitization. These T cells were unable, however, to passively transfer CHS to naive recipients. Animals treated with anti-SLC Ab during hapten sensitization were not tolerant to subsequent sensitization and challenge with the hapten. In addition, anti-SLC Ab did not inhibit CHS responses when given at the time of hapten challenge. These results indicate an important role for SLC during sensitization for CHS and suggest a strategy to circumvent functional T cell priming for inflammatory responses through administration of an Ab inhibiting dendritic cell trafficking.

Oral administration of hapten inhibits in vivo induction of specific cytotoxic CD8+ T cells mediating tissue inflammation: a role for regulatory CD4+ T cells

We investigated whether oral tolerance could block the development of an inflammatory response mediated by CD8+ T cells, using a mouse model of oral tolerance of contact sensitivity (CS) to the hapten 2, 4-dinitrofluorobenzene (DNFB). In this system, the skin inflammatory response is initiated by hapten-specific class I-restricted cytotoxic CD8+ T (CTL) cells, independently of CD4 help. Oral delivery of DNFB before skin sensitization blocked the CS response by impairing the development of DNFB-specific CD8+ effector T cells in secondary lymphoid organs. This was shown by complete inhibition of DNFB-specific CTL and proliferative responses of CD8+ T cells, lack of specific IFN-gamma-producing CD8+ T cells, and inability of CD8+ T cells to transfer CS in RAG20/0 mice. RT-PCR and immunohistochemical analysis confirmed that recruitment of CD8+ effectors of CS in the skin at the site of hapten challenge was impaired in orally tolerized mice. Sequential anti-CD4 Ab treatment showed that only depletion of CD4+ T cells during the afferent phase of CS abrogated oral tolerance induction by restoring high numbers of specific CD8+ effectors in lymphoid organs, whereas CD4 depletion during the efferent phase of CS did not affect oral tolerance. These data demonstrate that a single intragastric administration of hapten can block in vivo induction of DNFB-specific CD8+ CTL responsible for tissue inflammation and that a subset of regulatory CD4+ T cells mediate oral tolerance by inhibiting expansion of specific CD8+ effectors in lymph nodes.

Contact hypersensitivity responses following ribavirin treatment in vivo are influenced by type 1 cytokine polarization, regulation of IL-10 expression, and costimulatory signaling

We previously described the promotion of type 1 cytokine responses by the nucleoside analogue, ribavirin, in human T cells in vitro. In this study, we examined whether type 1 cytokine polarization by ribavirin in vivo could promote contact hypersensitivity (CHS) responses to dinitrofluorobenzene, a type 1 cytokine-mediated immune response. Unexpectedly, although type 1 cytokine responses were enhanced following ribavirin treatment in vitro and in vivo, the magnitude of CHS responses in BALB/c and C57BL/6 mice was influenced more by a second ribavirin-regulated pathway. The key regulatory molecule in this pathway was IL-10. Ribavirin-mediated suppression of IL-10 in BALB/c mice was associated with increased B7-2 expression and enhanced CHS responses, whereas enhanced IL-10 levels, following ribavirin administration, led to increased B7-1 expression and impaired CHS responses in C57BL/6 mice. The effect of ribavirin on the expression of B7 molecules and on CHS responses was neutralized by IL-10 administration in BALB/c and by anti-IL-10 Ab in C57BL/6. Thus, ribavirin controlled CHS responses directly through the modulation of IL-10 expression, and in vivo outcome was dictated by the preferential expression of either B7-1, an inappropriate costimulatory molecule in CHS, or B7-2, the predominant costimulatory molecule in CHS. Replacing dinitrofluorobenzene priming with IFN-alpha stimulation, we showed that the ribavirin-regulated pathway could function independent of Ag priming. Altogether, these data showed that, although ribavirin treatment induced a type 1 cytokine bias in contact allergen-primed BALB/c and C57BL/6 mice, in vivo CHS responses were dependent on ribavirin-mediated regulation of both IL-10 and preferential costimulatory signaling.

Regulation of T lymphocyte trafficking into lymph nodes during an immune response by the chemokines macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta

By virtue of their target cell specificity, chemokines have the potential to selectively recruit leukocyte subpopulations into sites of inflammation. Their role in regulation of T lymphocyte traffic into lymph nodes during the development of an immune response has not previously been explored. The sensitization phase of contact hypersensitivity induced by the hapten, dinitrofluorobenzene (DNFB) in the mouse was used as a model of T lymphocyte trafficking in response to antigenic stimulation. Rapid accumulation of CD8+ and CD4+ T cells in the draining lymph nodes was closely associated with strongly enhanced expression of macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta mRNAs and proteins. Mast cells accumulating in the nodes during DNFB sensitization were the predominant source of MIP-1 beta, whereas MIP-1 alpha was expressed by multiple cell types. Neutralization of these chemokines profoundly inhibited T lymphocyte trafficking into lymph nodes and altered the outcome of a subsequent challenge to DNFB. Thus, beta-chemokines regulate T lymphocyte emigration from the circulation into lymph nodes during an immune response and contribute significantly to the immunologic outcome.

Suppressive effect of ultraviolet B radiation on contact sensitization in mice. II. Systemic immunosuppression is modulated by ultraviolet irradiation and hapten application

Irradiation of mice with ultraviolet-B (UVB) can suppress contact hypersensitivity "systemically", even if hapten is applied to the non-irradiated skin site. We previously reported the factors influencing UVB-induced "local" immunosuppression. To obtain the most effective systemic immunosuppression, we further investigated the effect of the following factors on contact hypersensitivity to dinitrofluorobenzene (DNFB): UVB dose, dividing exposure, timing of sensitization after irradiation, area of exposure, hapten concentration, age, and genetic basis. The suppression was enhanced by increasing UVB dose. When 1 J/cm2 of UVB was exposed, 4 daily divided exposures (0.25 J/cm2 x 4) was more suppressive than a single (1 J/cm2 x 1) or double divided (0.5 J/cm2 x 2) exposure. Five or 10 day intervals between irradiation and sensitization induced stronger suppression than 1 or 3 day intervals. When the total energy (Joule, J) was kept constant, the exposure of low dose-UVB to a large area (0.5 J/ cm2 x 16.45 cm2) suppressed contact hypersensitivity more strongly than did high dose-UVB to a small area (2 J/cm2 x 4.11 cm2). When 25 ml of DNFB solution was applied, high concentration induced lower suppression. The stronger suppression was most prominent in the young (7 week) than in the old (22 week) mice. No difference was found in the systemic immunosuppression between C3H/HeN and Balb/c mice. These results suggest that not only UVB dose but also various factors should be taken into consideration to effectively induce systemic immunosuppression.

Lack of oral tolerance but oral priming for contact sensitivity to dinitrofluorobenzene in major histocompatibility complex class II-deficient mice and in CD4+ T cell-depleted mice

Oral tolerance is defined by immune unresponsiveness after oral administration of soluble antigens and by antigen-specific inhibition of peripheral immune responses induced by prior antigen feeding. The aim of this study was to investigate the implication of the major histocompatibility complex (MHC) class II presentation pathway to CD4+ T cells in oral tolerance of contact sensitivity (CS) to the hapten dinitrofluorobenzene (DNFB). We used MHC class II knockout (AB0/0) and invariant chain knockout (Ii0/0) mice, which have, respectively, a total or partial defect in class II-restricted activation of CD4+ T cells, as well as normal C57BL/6 mice depleted of CD4+ T cells by injection of a specific antibody. Intragastric administration of DNFB prior to skin sensitization induced specific inhibition of contact sensitivity to DNFB in A beta +/0 and Ii+/0 heterozygotes comparable to that observed in C57BL/6 mice. In contrast, no oral tolerance was observed in either MHC class II-deficient A beta 0/0 and Ii0/0 homozygote mutants or in syngeneic anti-CD4-depleted C57Bl/6 mice. Moreover, a single oral administration of DNFB, without skin sensitization, could prime A beta 0/0, Ii0/0 as well as anti-CD4-depleted C57BL/6 mice for DNFB-specific CS. These findings demonstrate that the class II/CD4 pathway is involved in oral tolerance manifested both as the inhibition of CS by hapten feeding prior to skin sensitization, and as immune unresponsiveness of normal mice to oral administration of hapten. Furthermore, our data provide evidence that a single oral feeding with DNFB is able to prime mice for hapten-specific CS, provided that the class II/ CD4 pathway is bypassed.

Neutralization of IL-12 in vivo prevents induction of contact hypersensitivity and induces hapten-specific tolerance

IL-12 is a heterodimeric cytokine with a powerful positive regulatory influence on the development of Th1 cell-mediated immune responses. Th1 cells are critically involved in contact hypersensitivity (CHS), so we were interested in studying whether IL-12 is of relevance in the induction phase of CHS. BALB/c mice were sensitized by epicutaneous application of 0.5% 2,4-dinitrofluorobenzene (DNFB) on the abdomen, draining lymph nodes obtained at various time points thereafter. RNA was extracted, and PCR analysis was performed using primers specific for the IL-12 subunits p35 and p40. Although p35 was constitutively expressed and not affected by hapten application, p40 transcripts were found to be enhanced in lymph nodes obtained between 12 and 24 h after sensitization. To study whether IL-12 is functionally relevant for the induction of CHS, an mAb directed against recombinant murine IL-12 was injected i.p. 3 and 24 h before sensitization. Challenge was performed 5 days later by painting the left ear with 0.3% DNFB. Whereas mice injected with sodium chloride or an isotype control Ab responded with a normal ear swelling after challenge with DNFB, mice treated with anti-IL-12 Ab showed a significantly reduced ear swelling response. To study whether injection of the IL-12 Ab causes transient nonresponsiveness or tolerance, resensitization was performed after a resting period of 14 days. Groups of mice initially treated with the anti-IL-12 Ab plus DNFB showed only a minimal response to DNFB after resensitization, suggesting that these mice became tolerant. Tolerance appeared to be hapten-specific because these mice could be successfully sensitized with the nonrelated hapten 2,4,6-trinitrochlorobenzene. Furthermore, when the anti-IL-12 Ab was injected into already sensitized mice before challenge, ear swelling response was significantly suppressed, suggesting that IL-12 also is involved in the effector phase of CHS. To exclude the possibility that the inhibitory effect of the anti-IL-12 Ab is simply due to an anti-inflammatory activity of the Ab, the anti-IL-12 Ab was injected i.p. 3 and 24 h before epicutaneous application of the toxic compound croton oil. However, irritant dermatitis elicited by croton oil was not affected by the Ab. Thus, the present study demonstrates that in vivo application of an anti-IL-12 Ab inhibits sensitization and induces hapten-specific tolerance and thus suggests that IL-12 may play a dominant in vivo role in the induction of CHS.

Neuropeptide modulation of chemically induced skin irritation

This study addresses the hypothesis that the early symptoms of chemically induced skin irritation are neurally mediated. Several approaches were used to affect nerve transmission in adult Balb/c female mice. These included general anesthesia (i.e., sodium pentobarbital), systemic capsaicin treatment, and pretreatment with specific pharmacological antagonists of the neuropeptides substance P (SP) and neurokinin A (NKA). After these treatments, a strongly irritating dose of dinitrofluorobenzene (DNFB) was applied to the ear and its swelling was measured over several postexposure times as an index of tissue irritation. Ear swelling in Nembutal (30 mg/kg)-anesthetized mice was depressed 62 and 76% at 4 and 24 hr postexposure compared to DNFB-treated unanesthetized animals measured at the same time points. Multiple injections of capsaicin (cumulative dose 30 mg/kg) depressed DNFB-ear swelling relative to non-capsaicin, DNFB-treated controls by 15, 40 (ip), and 44 and 43% (sc) at 4 and 24 hr postexposure, respectively. In mice exposed to acute or multiple injections of the SP antagonist CP-96,345 before DNFB application, ear swelling was depressed (relative to DNFB-treated animals) by 64 and 36% (acute, sc, 10 mg/kg) and 91 and 88% (multiple, ip, cumulative 35 mg/kg) at 0.5 and 1 hr postexposure, respectively. Mice exposed to the NKA antagonist, SR 48968, alone and in combination with the SP antagonist CP-96,345 were also examined after DNFB application. Ear swelling was diminished in mice pretreated with the NKA antagonist (1.0 mg/kg) by 17, 24, 34, and 40% at 0.5, 1, 4, and 24 hr postexposure. When used in combination with the SP antagonist, DNFB-induced ear swelling was reduced by 95% compared to unantagonized, DNFB-exposed mice at the 0.5- and 1-hr time points and remained significantly depressed by 33 and 46% at 4 and 24 hr postexposure. Taken in concert, these data suggest that neuropeptides, especially the tachykinins SP and NKA, modulate the early stages of chemically induced skin irritation.

Effects of immunological responsiveness on Langerhans cell behavior in contact sensitization

The epicutaneous application of haptens results in a functional activation of the antigen-presenting Langerhans cells (LCs) which is necessary for the induction of contact sensitivity. In this ultrastructural study, we investigated the effects of the immune response on these cellular properties of the LCs by using 2 strains of guinea pigs with genetically determined high and non responsiveness, respectively, to the strong sensitizer 2,4-dinitrochlorobenzene (DNCB). After skin painting, both strains showed a similar cellular and endocytotic activation of the LCs and a similar intraepidermal localization of DNCB on immunoelectron microscopical visualization. There were however few LC-lymphoid cell interactions in the non responders, in contrast to numerous such appositions in the other strain. Intravenous tolerization with 2,4-dinitrobenzene-1-sulfonic acid, which is known to block the DNCB receptor of T cells, hampered the lymphoid cell interactions in the DNCB treated high responders, but it did not affect the LC activation. These in vivo observations demonstrate that the hapten-induced changes of the LC properties is the initial, T-cell independent event in contact sensitization.

Tumor necrosis factor alpha polymorphism correlates with deleterious effects of ultraviolet B light on cutaneous immunity

Intradermally injected tumor necrosis factor alpha (TNF-alpha) mimics the effects of UV B light (UVB) radiation and neutralizing anti-TNF-alpha antibodies abolish the deleterious effects of UVB on induction of contact hypersensitivity suggesting that TNF-alpha is the major mediator of UVB effects on cutaneous immunity. In the present study we have shown that in lipopolysaccharide-sensitive inbred strains of mice, the ability of acute, low-dose UVB radiation to impair the induction of contact hypersensitivity to dinitrofluorobenzene is genetically determined by polymorphic alleles at the Tnf alpha locus. We have analyzed by the sequence analysis and restriction fragment length polymorphism the Tnf alpha alleles of numerous inbred strains expressing UVB susceptibility (UVB-S) and UVB-resistance (UVB-R). The Tnf alpha alleles of all UVB-R, but not UVB-S, strains contain a BamHI site in the first intron. Moreover, the 5' regulatory region of the Tnf alpha allele of UVB-R mice possesses a (CA)14 minirepeat that is located immediately 5' of the cytokine response element nearest the tumor-associated transplantation antigen box. By contrast, the Tnf alpha alleles of UVB-S mice display repeats of < > 14 at this site. It is proposed that the unique microsatellite of UVB-R mice impairs transcriptional efficiency at Tnf alpha compared to UVB-S mice and that the quantitative difference in Tnf alpha produced intracutaneously in response to UVB radiation accounts for the phenotypic traits of UVB-R and UVB-S.

Increased level of intracellular MHC class II molecules in murine Langerhans cells following in vivo and in vitro administration of contact allergens

Treatment of murine Langerhans cells (LC) with contact allergens results in increased internalization of cell membrane constituents and therefore in depressed cell-surface expression of major histocompatibility complex (MHC) class II molecules during the first hours after haptenization. In this presentation we show that this downregulation of cell-surface-expressed Ia-antigens is accompanied by an augmentation of the intracellular pool of MHC class II molecules. Rat MoAb 2G9 was developed, which recognizes IA and IE molecules of the d-haplotype. This MoAb competes with the murine MoAb MK-D6 for binding sites to IAd-molecules. After blocking the cell-surface-expressed molecules with 2G9 and permeabilizing the cell membranes this allowed us to measure selectively the intracellular amount of IA molecules by double immunofluorescence staining and flow cytometric analysis. Cell-surface expression of IA molecules was found to be depressed but their internal pool was significantly elevated following in vivo treatment with the contact allergens DNFB, DNCB, oxazolone, and K2Cr2O7 for 3 h. In vitro culture of freshly prepared LC in the presence of 1 microgram/ml DNFB yielded similar results. Blocking of protein biosynthesis with cycloheximide did not prevent this intracellular class II accumulation. An augmented representation of internalized class II molecules in haptenized LC might play an important role in the presentation of contact allergens.

Deleterious effects of cis-urocanic acid and UVB radiation on Langerhans cells and on induction of contact hypersensitivity are mediated by tumor necrosis factor-alpha

Ultraviolet B (UVB) light disrupts epidermal Langerhans cells (LC) universally and impairs the induction of contact hypersensitivity (CH) to epicutaneously applied haptens in certain strains of mice. Similar effects are observed when tumor necrosis factor-alpha (TNF alpha) is injected intradermally (ID) in mice. Trans-urocanic acid (UCA), a photoreceptor for UVB radiation, is known to be immunosuppressive. To determine whether cis-UCA is important in the process by which UVB and/or TNF alpha act in the skin, cis-UCA was injected ID into C57BL/6, C3H/HeN, BALB/c, and C3H/HeJ mice. Whole mounts of epidermis were removed 5 h later and stained immunochemically with anti-Ia antibodies. Microscopy revealed that Ia-bearing LC had lost their dendrites, had rounded up, and were reduced in number in all strains examined. Moreover, when dinitrofluorobenzene (DNFB) was applied epicutaneously to the injected site, induction of CH was grossly impaired. When neutralizing anti-TNF alpha antibodies were administered intraperitoneally 2 h prior to ID injection of cis-UCA, the deleterious effects on LC and CH induction were largely reversed. These results indicate that the actions of cis-UCA on LC and on CH induction are very similar to those achieved by ID injections of TNF alpha and by cutaneous exposure to low-dose UVB. Because the effects of UVB radiation and cis-UCA are reversed by anti-TNF alpha antibodies, we propose that UVB radiation impairs the induction of CH in mice by converting trans-UCA to cis-UCA within the epidermis; cis-UCA in turn causes the local release of TNF alpha, which thwarts sensitization by its ability to alter the functional program of epidermal Langerhans cells, thereby preventing the induction of CH.

Suppression of cell-mediated immunity by purified aflatoxin B1 in broiler chicks

The effect of purified aflatoxin B1 on cell-mediated immunity (CMI) in broiler chicks was assessed using doses of 0.3 and 1 mg/kg feed from hatching to 6 weeks of age. Total lymphocyte and T lymphocyte counts and the 2,4-dinitrofluorobenzene skin sensitivity test, graft-versus-host reaction and nitroblue tetrazolium salt reduction tests were used to evaluate CMI. Both doses of aflatoxin B1, including the apparently nontoxic dose of 0.3 mg/kg feed, caused a significant (P less than 0.05) decline in CMI. The functional activity of splenic macrophages was decreased significantly (P less than 0.05) by both doses of the toxin.

Effect of vitamin A in enteral formulae for burned guinea-pigs

A burned guinea-pig model (30 per cent body surface area) was used to study the effects of dietary vitamin A. Sixty-five female guinea-pigs were infused enterally via gastrostomy feeding tubes with identical formulate (175 kcal/kg/day, 20 per cent of calories as protein) containing varying amounts of vitamin A. Groups I, II, III and IV received formulae containing 0, 10,000 iu (approximately equivalent to the guinea-pigs' RDA), 50,000 iu (5 x RDA) and 250,000 iu (25 x RDA) of vitamin A per litre, respectively. After 14 days of tube feeding, the animals were killed. Group I animals had evidence of vitamin A deficiency including low haemoglobin levels, lower red blood cell counts and lower caecal mucosal weight. Findings of hypervitaminosis A were observed only in animals given the highest dose of vitamin A (25 x RDA). These were elevated serum alkaline phosphatase and complement C3 levels and enlarged adrenal glands. Group IV also showed defective cell-mediated immunity as reflected by reduced delayed cutaneous response to dinitrofluorobenzene. In a second experiment groups I, II, III and IV were given formulas containing 0, 1 x RDA, 5 x RDA, and 10 x RDA of vitamin A respectively for 14 days. Through postburn days 12 to 14 they were injected subcutaneously with 3 x 10(8) of Staphylococcus aureus once daily. On postburn day 15 the animals were killed and the numbers of viable bacteria at each injection site were counted. No significant differences were observed in viable bacterial numbers between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigen-presenting cells in the induction of contact hypersensitivity in mice: evidence that Langerhans cells are sufficient but not required

One explanation for the fact that certain genetically defined strains of mice prove to be resistant to effects of low dose ultraviolet B radiation on the induction of contact hypersensitivity is that ultraviolet B resistant mice possess a second pathway for antigen presentation through the skin--a pathway that is independent of epidermal Langerhans cells and beyond the reach of the damaging effects of ultraviolet B light. As a corollary, ultraviolet-B susceptible mice would be expected to be deficient in this pathway. Several experimental strategies were employed to determine whether Langerhans cells are required for the induction of contact hypersensitivity by epicutaneously applied hapten. The results reveal that tape-stripped skin supports the induction of contact hypersensitivity, whereas surgical excision of hapten-painted skin within 1 h of application fails to permit the development of contact hypersensitivity. Because the former selectively eliminates epidermal Langerhans cells while the latter deletes both Langerhans cells and dermal antigen-presenting cells, we conclude that either Langerhans cells or dermal cells are sufficient to provide antigen presentation in the induction of contact hypersensitivity. When large amounts of hapten are painted epicutaneously, or when hapten is injected subcutaneously or painted on sub-dermal tissues, contact hypersensitivity also results, indicating that induction of contact hypersensitivity does not require that antigen processing and presentation be provided by cutaneous cells. Reasons are presented for concluding that under physiologic circumstances induction of contact hypersensitivity by epicutaneous hapten application relies primarily upon the antigen-presenting capabilities of epidermal (Langerhans cells) and dermal cells.

Flare-up reaction on murine contact hypersensitivity. I. Description of an experimental model: rechallenge system

In this experiment, a 'rechallenge system' was established in BALB/c mice to study a local immunological reaction of contact hypersensitivity (CH). Briefly, mice were sensitized by a single painting with 25 microliters of 0.5% dinitrofluorobenzene (DNFB) on the shaved back skin on Day 0. On Day 5, they were challenged with 20 microliters of 0.2% DNFB on each left ear, and on Day 33 challenged again with either painting 20 microliters of 0.2% DNFB on their both ears or intravenous administration of 15 mg of dinitrobenzene sulphonic acid (DNBS). As the result, marked ear swelling was observed by the second challenge only on the first challenged site and these responses were clarified to be antigen specific. In in vitro experiments, it was shown that only the cells from the regional lymph node of the skin, which were previously elicited on challenge, were enhanced to proliferate by DNBS, which was added into the culture medium. These results suggest that there is a local immunological mechanism to respond to the specific antigen only on the site in which CH reaction has been elicited previously. The results from this 'rechallenge system' may help to explain some pathological mechanisms of such chronic diseases as fixed drug eruption or chronic contact dermatitis, which recur easily in skin lesions involved previously.

ATPase and morphologic changes in Langerhans cells induced by epicutaneous application of a sensitizing dose of DNFB

We have previously described an ATPase Langerhans cell (LC) staining technique allowing progression from light to electron microscope observation. Using this technique we have studied, following epicutaneous application of a sensitizing dose of a hapten, 2,4-dinitro-1-fluorobenzene (DNFB), the fate of the epidermal LC located in the sensitization zone. We wanted to know, under the light microscope, if the density and/or morphology of the LC are modified by such a treatment and, under the electron microscope, what are the ultrastructural changes accompanying the possible light microscope modifications. Under the light microscope, the observation of LC during the 5 d necessary for the development of contact sensitivity to DNFB shows that their number drops in the course of the first 24 h to normalize again 3 d later. Under the electron microscope, observations over the first 24 h revealed that LC remained in the epidermis, but were ATPase-negative. The disappearance of the membrane ATPase activity took place while the LC presented an increased number of coated pits, coated vesicles, endosomes, and lysosome organelles which characterize, at the ultrastructural level, the process of receptor-mediated endocytosis (RME). Following RME, many Birbeck granules (BG) appeared in the cytoplasm. Thus, epicutaneous application of DNFB leads to an endocytic activation of LC. However, the ligand(s) and/or the cell-surface components, which probably internalize during the RME process, remain unknown.

Local murine recombinant gamma interferon enhances the acquisition of allergic contact dermatitis in the mouse

Using the model of allergic contact dermatitis in mice, we have demonstrated that local administration of recombinant (r) murine gamma interferon (gamma-rIFN) to the sensitization site substantially enhances the acquisition of delayed-type hypersensitivity. Single doses of gamma-rIFN from 500 to 2,000 U immunopotentiate successfully, with a suggestion of a better response at the higher doses. The immunoadjuvant effect is lost when the injections of gamma-rIFN are at a site distant from the sensitization site. Kinetic studies imply that gamma-rIFN is most effective when given at the time of sensitization, but significant immunopotentiation can be seen when gamma-rIFN is given several days before or after sensitization.