DOCK8 Expression in Regulatory T Cells Maintains their Stability and Limits Contact Hypersensitivity

Chronic dermatitis is a hallmark of Dedicator of cytokinesis 8 (DOCK8) deficiency. The migration of DOCK8-deficient T cells to the skin and their survival there have been reported to be defective. Surprisingly, we found that Dock8^-/- mice demonstrated an exaggerated contact hypersensitivity (CHS) response to oxazolone with increased ear swelling, T-cell infiltration, and expression of Ifng. To understand the mechanisms of persistent skin inflammation in DOCK8 deficiency, we examined mice with selective deficiency of DOCK8 in T cells or T regulatory cells (Tregs) and found that both have exaggerated CHS. Moreover, oral tolerance to oxazolone, mediated by Tregs, was impaired in Dock8^-/- mice. Transfer of Tregs from oxazolone-sensitized wild-type mice, but not Dock8^-/- mice, reduced the CHS response of Dock8^-/- recipients. Lack of DOCK8 in Tregs resulted in their acquisition of a pathogenic FOXP3⁺T-bet⁺IFNγ⁺ phenotype at CHS sites and promoted their conversion into ex-Tregs. The transfer of Tregs from Dock8^-/- mice increased the CHS response of wild-type recipients to oxazolone. Thus, DOCK8 expression in Tregs limits CHS by promoting Treg stability and fitness in inflamed skin. Interventions aimed at ameliorating Treg function may be useful in treating skin inflammation in DOCK8 deficiency.

Successful development of methodology for detection of hapten-specific contact hypersensitivity (CHS) memory in swine

Hapten contact hypersensitivity (CHS) elicits a well-documented inflammation response that can be used to illustrate training of immune cells through hapten-specific CHS memory. The education of hapten-specific memory T cells has been well-established, recent research in mice has expanded the “adaptive” characteristic of a memory response from solely a function of the adaptive immune system, to innate cells as well. To test whether similar responses are seen in a non-rodent model, we used hapten-specific CHS to measure the ear inflammation response of outbred pigs to dinitrofluorobenzene (DNFB), oxazolone (OXA), or vehicle controls. We adapted mouse innate memory literature protocols to the domestic pig model. Animals were challenged up to 32 days post initial sensitization exposure to the hapten, and specific ear swelling responses to this challenge were significant for 7, 21, and 32 days post-sensitization. We established hapten-specific CHS memory exists in a non-rodent model. We also developed a successful protocol for demonstrating these CHS responses in a porcine system.

Keratinocyte Proline-Rich Protein Deficiency in Atopic Dermatitis Leads to Barrier Disruption

Atopic dermatitis is a common inflammatory skin disease caused by the interaction of genetic and environmental factors. By allelic copy number analysis at missense single-nucleotide polymorphisms on 26 genes with copy number variation, we identified a significant association between atopic dermatitis and human KPRP. Human KPRP expression, which was localized to the upper granular layer of epidermis, was significantly decreased in atopic dermatitis compared with normal skin. KPRP was histologically colocalized with loricrin and was mainly detected in cytoskeleton fractions of human keratinocytes. To further investigate the role of KPRP in skin, Kprp-knockout mice were generated. Heterozygous knockout (Kprp^+/-) mice exhibited reduced KPRP expression to level a similar to that of human AD lesional skin. Kprp^+/- mice showed abnormal desmosome structure and detachment of lower layers of the stratum corneum. Percutaneous inflammation by topical application of croton oil or oxazolone was enhanced, and epicutaneous immunization with ovalbumin induced a high level of IgE in Kprp^+/- mice. Our study, started from allelic copy number analysis in human AD, identified the importance of KPRP, the decrease of which leads to barrier dysfunction.

Lymphatic vessel function in head and neck inflammation

BACKGROUND

Serious infections of the head and neck cause lymphedema that can lead to airway compromise and oropharyngeal obstruction. Lymphangiogenesis occurs in the head and neck during infection and after immunization. The goal of this project was to develop tools to image lymphatic vessels in living animals and to be able to isolate individual lymphatic endothelial cells in order to quantify changes in single cells caused by inflammation.

METHODS

The ProxTom transgenic red-fluorescent reporter mouse was developed specifically for the purpose of imaging lymphatic vessels in vivo. Prox1 is a transcription factor that is necessary for lymphangiogenesis in development and for the maintenance of lymphatics in adulthood. Mice were immunized and their lymphatic vessels in lymph nodes were imaged in vivo. Individual lymphatic endothelial cells were isolated by means of their fluorescence.

RESULTS

The ProxTom transgene has the red-fluorescent reporter td-Tomato under the control of Prox1 regulatory elements. tdTomato was faithfully expressed in lymphatic vessels coincident with endogenous Prox1 expression. We show lymphangiogenesis in vivo after immunization and demonstrate a method for the isolation of lymphatic endothelial cells by their tdTomato red-fluorescence.

CONCLUSIONS

The faithful expression of the red-fluorescent reporter in the lymphatic vessels of ProxTom means that these mice have proven utility for in vivo study of lymphatic vessels in the immune response. ProxTom has been made available for distribution from the Jackson Laboratory: http://jaxmice.jax.org/strain/018128.html .

Intranasally administered antigen 85B gene vaccine in non-replicating human Parainfluenza type 2 virus vector ameliorates mouse atopic dermatitis

Atopic dermatitis (AD) is a refractory and recurrent inflammatory skin disease. Various factors including heredity, environmental agent, innate and acquired immunity, and skin barrier function participate in the pathogenesis of AD. T -helper (Th) 2-dominant immunological milieu has been suggested in the acute phase of AD. Antigen 85B (Ag85B) is a 30-kDa secretory protein well conserved in Mycobacterium species. Ag85B has strong Th1-type cytokine inducing activity, and is expected to ameliorate Th2 condition in allergic disease. To perform Ag85B function in vivo, effective and less invasive vaccination method is required. Recently, we have established a novel functional virus vector; recombinant human parainfluenza type 2 virus vector (rhPIV2): highly expressive, replication-deficient, and very low-pathogenic vector. In this study, we investigated the efficacy of rhPIV2 engineered to express Ag85B (rhPIV2/Ag85B) in a mouse AD model induced by repeated oxazolone (OX) challenge. Ear swelling, dermal cell infiltrations and serum IgE level were significantly suppressed in the rhPIV2/Ag85B treated mouse group accompanied with elevated IFN-γ and IL-10 mRNA expressions, and suppressed IL-4, TNF-α and MIP-2 mRNA expressions. The treated mice showed no clinical symptom of croup or systemic adverse reactions. The respiratory tract epithelium captured rhPIV2 effectively without remarkable cytotoxic effects. These results suggested that rhPIV2/Ag85B might be a potent therapeutic tool to control allergic disorders.

Toll-like receptor 2 is important for the T(H)1 response to cutaneous sensitization

BACKGROUND

Atopic dermatitis and allergic contact dermatitis are skin disorders triggered by epicutaneous sensitization with protein antigens and contact sensitization with haptens, respectively. Skin is colonized with bacteria, which are a source of Toll-like receptor (TLR) 2 ligands.

OBJECTIVE

We sought to examine the role of TLR2 in murine models of atopic dermatitis and allergic contact dermatitis.

METHODS

TLR2(-/-) mice and wild-type littermates were epicutaneously sensitized with ovalbumin (OVA) or contact sensitized with oxazolone (OX). Skin histology was assessed by means of hematoxylin and eosin staining and immunohistochemistry. Ear swelling was measured with a micrometer. Cytokine mRNA expression was examined by means of quantitative RT-PCR. Antibody levels and splenocyte secretion of cytokines in response to OVA stimulation were measured by means of ELISA. Dendritic cells were examined for their ability to polarize T-cell receptor/OVA transgenic naive T cells to T(H)1 and T(H)2.

RESULTS

In response to OVA sensitization, TLR2(-/-) mice experienced skin infiltration with eosinophils and CD4(+) cells, as well as upregulation of T(H)2 cytokine mRNAs that was comparable with that seen in wild-type littermates. In contrast, epidermal thickening, IFN-gamma expression in the skin, IFN-gamma production by splenocytes, and IgG2a anti-OVA antibody levels were impaired in TLR2(-/-) mice. After OX ear challenge, contact sensitized TLR2(-/-) mice exhibited defective ear swelling with impaired cellular infiltration, decreased epidermal thickening and local IFN-gamma expression, and impaired OX-specific IgG2a responses. Dendritic cells from TLR2(-/-) mice induced significantly lower production of IFN-gamma but normal IL-4 and IL-13 production in naive T cells.

CONCLUSIONS

These results indicate that TLR2 promotes the IFN-gamma response to cutaneously introduced antigens.

Chinese herbal medicine (Tuhuai extract) exhibits topical anti-proliferative and anti-inflammatory activity in murine disease models

While psoriasis is one of the most common skin disorders in humans, effective, safe and inexpensive treatments are still largely unavailable. Chinese herbal medicine (CHM) has been used for centuries for treating psoriasis and several reports claim that systemic administration of one such CHM, Tuhuai, mainly composed of flos sophorae, smilax glabra roxb and licorice, is effective in psoriasis. However, the mechanisms by which this CHM improves psoriasis are not yet clear. Two universal features of psoriasis are epidermal hyperplasia and inflammation. Moreover, drugs that specifically inhibit epidermal hyperplasia and/or inflammation are widely used to treat psoriasis. Here, we investigated whether topical applications of Tuhuai extract exhibit anti-proliferative and anti-inflammatory activities in two murine models of inflammatory dermatoses. To assess Tuhuai's potential anti-proliferative effect, we disrupted epidermal barrier function twice-daily for 4 days in normal hairless mice followed by topical applications of either 1% Tuhuai extract or Vehicle to both flanks immediately after each barrier perturbation. Changes in epidermal proliferation and apoptosis were evaluated by immunohistochemistry and TUNEL staining. To assess the anti-inflammatory effects of Tuhuai, both irritant (phorbol ester) and acute allergic contact dermatitis (oxazolone) models were used. Whereas topical Tuhuai extract did not alter epidermal proliferation or induce irritation in normal skin, it both reduced epidermal hyperplasia in the epidermal hyperproliferative model, and reduced inflammation in both irritant and allergic contact dermatitis models. As topical Tuhuai extract exhibits anti-proliferative and anti-inflammatory properties in a variety of human models of inflammatory dermatoses, Tuhuai could provide an effective, relatively safe and inexpensive therapeutic alternative for the treatment of inflammatory dermatoses, including psoriasis.

Effect of skin painting with oxazolone on the local extravasation of mononuclear cells in sheep

A characteristic feature of the induction of cell-mediated delayed hypersensitivity reactions by chemicals such as oxazolone is the enlargement of lymphocyte traffic areas in the paracortices of regional lymph nodes. In sheep oxazolone is a powerful immunogen but the cellular changes in lymph efferent from nodes draining areas of oxazolone-painted skin do not differ significantly from responses to conventional antigens. Specific complement-binding antibodies appear in the plasma of sensitized sheep, which respond to secondary challenges with an immediate Arthus reaction. In studies of peripheral lymph from areas of skin painted with oxazolone the number of mononuclear cells in the lymph increased 10--50-fold two days or so after skin painting. Most of these cells were small lymphocytes lacking surface immunoglobulin (presumptive 'T' cells). This big increase in lymphocyte traffic through the skin may be a consequence of the binding to local structural proteins of myriads of oxazolone epitopes. If so, and bearing in mind the large doses of immunogen used in experiments on mice, it is easy to envisage how the traffic areas of lymph nodes expand and become congested with lymphocytes after being flooded with a highly immunogenic and reactive chemical like oxazolone. Whether this is relevant to the induction of cell-mediated immunity is unknown.

Thymus-independent type 2 antigen induces a long-term IgG-related network memory

Thymus-independent type 2 (TI-2) antigens occasionally induce long-lasting IgM memory, but do not prime for typical secondary IgG responses. However, contrary to current understanding, we detected several TI-2-induced long-term memory effects in subsequent thymus-dependent (TD) responses to the hapten 2-phenyloxazolone coupled to a protein carrier. The early primary TD response, even 3 months after TI-2 immunization, included non-mutated IgM as well as IgG antibodies exhibiting higher affinities than the Ox1 idiotype which dominates and has highest affinity in sole TD responses. The secondary exclusive IgG response 8 weeks later contained major hitherto non-observed clones. Somatic hypermutation on the normally dominant V(H)Ox1 gene was largely silenced while the associated VkappaOx1 exhibited the classical affinity-enhancing mutations, thus suggesting a separate regulation of this process for V(H) and V(L) genes. Mutations accumulated in genes which normally are rarely or non-expressed or non-mutating. First evidence is presented that receptor revision by V(H) replacement may occur during immune maturation in genetically non-engineered wildtype mice. We conclude that the TI-2 antigen-induced altered selection of TD Ag-inducible clones and its severe gene-specific influence on further somatic mutations and affinity maturation represents a network memory, which we hypothesize to be mediated by anti-idiotypic regulatory T cells.

T cells specific to hapten carrier but not to carrier alone assist in the production of anti-hapten and anti-carrier antibodies

We examined the immune response of Balb/c mice to antigens prepared by conjugating 2-phenyloxazolone (phOx) to a foreign protein, ovalbumin (OVA), or a self-protein, mouse serum albumin (MSA), in order to study how these chemical modifications would affect immune recognition. We found that anti-OVA antibodies and CD4(+) T cells produced by OVA immunization reacted with OVA as well as with phOx-OVA. Anti-phOx antibodies were produced by phOx-OVA immunization and, interestingly, T cells from these mice reacted only with phOx-OVA but not with the intact OVA. These results suggested that the classical model of hapten-carrier immunization, in which B cells specific to hapten are activated with assistance from T cells specific to a carrier protein, might not be a major route for production of anti-hapten antibodies in hapten-carrier immunization. Furthermore, phOx-MSA immunization induced production of anti-phOx antibodies, which could not be accounted for in terms of the assistance of carrier-specific T cells because of the absence of MSA-specific T cells. Therefore, we proposed a new model in which anti-hapten B cells are assisted by T cells specific to the haptenated carrier.

Characterization of a hapten-induced, murine model with multiple features of atopic dermatitis: structural, immunologic, and biochemical changes following single versus multiple oxazolone challenges

Atopic dermatitis (AD) is a chronic dermatosis bearing clinical, histological, and immunologic similarities to chronic allergic contact dermatitis (ACD). AD shows a Th2 cell-dominant inflammatory infiltrate, elevated serum IgE levels, a permeability barrier abnormality, and Staphylococcus aureus colonization. Repeated hapten challenges reportedly produce a Th2-like hypersensitivity reaction (Th2-like HR). Here, 9-10 challenges with oxazolone (Ox) to hairless mice also produced a chronic Th2-like HR. Permeability barrier function and expression of differentiation proteins, filaggrin, loricrin, and involucrin, became abnormal. CRTH-positive Th2-dominant inflammatory infiltrate, with increased IL-4 expression, and a large increase in serum IgE levels were observed. The barrier abnormality was associated with decreased stratum corneum (SC) ceramide content and impaired lamellar body secretion, resulting in abnormal lamellar membranes, as in human AD. Furthermore, as in human AD, epidermal serine protease activity in SC increased and expression of two lamellar body-derived antimicrobial peptides, CRAMP and mBD3, declined after Ox challenges, paralleling the decrease of their human homologues in AD. Thus, multiple Ox challenges to normal murine skin produce a chronic Th2-like HR, with multiple features of human AD. Because of its reproducibility, predictability, and low cost, this model could prove useful for evaluating both pathogenic mechanisms and potential therapies for AD.

Antigen-specific immunoglobulin E+ B cells are preferentially localized within germinal centres

Allergen-specific immunoglobulin E (IgE) mediates immediate-type hypersensitivity reactions and plays a central role in allergic diseases. Although antigen-driven B-cell maturation and isotype switching occur within germinal centres (GCs), the role of GCs in IgE production is poorly understood. In view of this, we investigated the development of IgE-expressing cells within GCs in response to an extensively characterized antigen, 2-phenyloxazolone (phOx). The phOx-specific IgE-expressing cells localized within GCs 7 days after immunization, and peaked in number on day 11. Surprisingly, very few IgE-positive cells were found in the T-cell areas of the lymph node. Flow cytometric studies confirmed that IgE was expressed by B cells and was not the result of trapping by follicular dendritic cells. The specificity of the antibody response was confirmed by microdissection and reverse transcription-polymerase chain reaction using phOx-specific IgE primers. IgE-positive cells were primarily found within GCs while, in contrast, many IgG1-positive cells could also be detected outside GCs in the T-cell areas. Taken together, these data highlight the importance of GCs in the production of antigen-specific IgE antibody.

Synchrony of High Endothelial Venules and Lymphatic Vessels Revealed by Immunization

The mature phenotype of peripheral lymph node (LN) high endothelial venules (HEVs), defined as MAdCAM-1(low) PNAd(high) LTbetaR(high) HEC-6ST(high), is dependent on signaling through the lymphotoxin-beta receptor (LTbetaR). Plasticity of PLN HEVs during immunization with oxazolone was apparent as a reversion to an immature phenotype (MAdCAM-1(high) PNAd(low) LTbetaR(low) HEC-6ST(low)) followed by recovery to the mature phenotype. The recovery was dependent on B cells and was inhibited by LTbetaR-Ig treatment. Concurrent with HEV reversion, at day 4 following oxazolone or OVA immunization, reduced accumulation of Evans blue dye and newly activated DCs in the draining LNs revealed a temporary afferent lymphatic vessel (LV) functional insufficiency. T cell priming to a second Ag was temporarily inhibited. At day 7, lymphangiogenesis peaked in both the skin and draining LN, and afferent LV function was restored at the same time as HEV phenotype recovery. This process was delayed in the absence of B cells. LV and HEV both express the LTbetaR. During lymphangiogenesis in the draining LN, HEV, and LV were directly apposed; some vessels appeared to express both PNAd and LYVE-1. Pretreatment with LTbetaR-Ig drastically reduced the number of PNAd+ LYVE-1+ vessels, suggesting a reduction in LV and HEV cross-talk. The concordance in time and function and the close physical contact between LVs and HEVs in the remodeling process after immunization indicate that the two vascular systems are in synchrony and engage in cross-talk through B cells and LTbetaR.

Interleukin 5 Plays an Essential Role in Elicitation of Contact Sensitivity through Dual Effects on Eosinophils and B-1 Cells

BACKGROUND

Elicitation of contact sensitivity (CS) depends on B-1-cell-derived antigen-specific immunoglobulin M (IgM) antibodies that recruit CS effector T cells into the local tissue, which is followed by infiltration of antigen-nonspecific mononuclear cells and polymorphonuclear cells, such as neutrophils and eosinophils. In this study, we investigated the role of interleukin (IL)-5, which has broad effects on both eosinophils and B-1 cells, in elicitation of CS.

METHODS

IL-5 receptor alpha-chain-deficient (IL-5Ralpha-/-) mice and IL-5Ralpha+/+ mice were contact sensitized with oxazolone hapten. Four days later, mice were challenged with the same hapten, and ear swelling responses were measured at 24 h after challenge. Eosinophil infiltration into the local tissue was determined by examination of skin histology and eosinophil peroxidase activity. To investigate the role of IL-5 in B-1 cell activation, the number of oxazolone-specific IgM-producing cells in the spleen was determined by enzyme-linked immunospot assay.

RESULTS

Ear swelling responses in IL-5Ralpha-/- mice were about half of those in IL-5Ralpha+/+ mice, and nearly no eosinophil infiltration was observed in IL-5Ralpha-/- mouse skin. Eosinophil peroxidase activity in the sensitized and challenged IL-5Ralpha-/- mice was about 11 times less than that in immunized IL-5Ralpha+/+ mice. Contact sensitization significantly increased in numbers of oxazolne-specific IgM-producing cells in IL-5Ralpha+/+ mouse spleen, but not in IL-5Ralpha-/- mouse spleen.

CONCLUSION

We conclude that IL-5-dependent activation of eosinophils and B-1 cells is necessary for induction and elicitation of CS. These findings provide a new insight into complicated mechanisms of CS elicitation and suggest a novel role of IL-5 in the regulation of immune responses.

Toll-like receptor ligands reverse suppression of contact hypersensitivity reactions induced by epicutaneous immunization with protein antigen

BACKGROUND

Epicutaneous (EC) immunization with protein antigens has been shown to induce antigen nonspecific suppression of subsequent T cell-dependent contact hypersensitivity (CS) reactions after active immunization. The aim of this work was to test if EC application of Toll-like receptor (TLR) ligands together with protein antigen could reverse suppression of CS.

METHODS

Mice were EC immunized by applying gauze patches soaked with a solution of protein antigen alone or in the presence of crude bacterial material (bacterial lysates or heat-killed bacteria) or purified TLR ligands and then tested for CS response. To test if reversal of EC-induced suppression is antigen-specific, mice were patched with TNP- or OX-substituted mouse Ig alone or together with LPS and then tested for CS with corresponding or non-cross-reacting hapten. Influence of EC immunization on cytokine production by lymph node cells was measured by ELISA.

RESULTS

EC immunization with protein antigen induces antigen nonspecific suppression that can be reversed by crude bacterial material as well as purified TLR-2, TLR-3, TLR-4, and TLR-9 ligands. The effect of TLR-4 ligand LPS was not observed in the Tlr-4 mutant C3H/HeJ mouse, indicating that this effect was dependent upon intact TLR-4 signaling. Unlike the antigen nonspecific suppression of CS by EC immunization with antigen alone, the reversal of suppression by TLR ligands was specific for the protein antigen applied in the EC protocol.

CONCLUSIONS

Our results strongly suggest that EC immunization with protein antigen together with TLR ligands induces a particular antigen-specific cell population, akin to previously described contrasuppressor cells, which protects immune cells against the action of suppressor cells but have no direct influence on antigen nonspecific suppressor cells induced by antigen alone.

Antibody buffering of a ligand in vivo

Clearance is the practical limit on drug action. Here we propose a means of slowing clearance, thereby extending drug lifetime in vivo by "antibody buffering." In this process, a drug and an anti-drug antibody are coadministered. Most of the drug is bound to the antibody, preventing the drug from acting, but also preventing its elimination. A dynamic free drug pool is established by reversible dissociation from the antibody. The free drug is active and can be eliminated, but the free pool is constantly replenished by reequilibration from the antibody-drug complex, giving a long effective lifetime. Here we explore antibody buffering experimentally by using a model compound, 2-phenyloxazol-5-one-gamma-aminobutyrate (Ox), as a drug proxy. We show that antibody buffering can extend by an order of magnitude the plasma lifetime of Ox in rats, and that the steady-state Ox level depends on the molecular properties of the antibody used to buffer the Ox. In addition, the anti-Ox antibody can be recharged with drug in vivo to extend Ox lifetime without additional antibody administration, making this technique even more suitable for possible clinical application.

Immune sensitization in the skin is enhanced by antigen-independent effects of IgE on mast cells

Contact sensitivity responses require both effective immune sensitization following cutaneous exposure to chemical haptens and antigen-specific elicitation of inflammation upon subsequent hapten challenge. We have observed that that antigen-independent effects of immunoglobulin E (IgE) antibodies promote immune sensitization to haptens in the skin. Contact sensitivity is markedly impaired in IgE-/- mice but can be restored by either transfer of sensitized cells from wild-type mice or administration of hapten-irrelevant IgE before sensitization. Moreover, IgE-/- mice exhibit impairment in the emigration of dendritic cells from the epidermis after hapten exposure. Monomeric IgE has been reported to influence mast cell function. We observe diminished contact sensitivity in mice lacking FcepsilonRI or mast cells, and mRNA for several mast cell-associated genes is reduced in IgE-/- vs. wild-type skin after hapten exposure. We propose that levels of IgE normally present in mice favour immune sensitization via antigen-independent effects on mast cells.

B cells are not required for T cell priming in low zone tolerance to contact allergens and contact hypersensitivity

Low zone tolerance (LZT) to contact allergens is induced by epicutaneous exposure to haptens in subsensitizing doses resulting in an inhibition of contact hypersensitivity (CHS), which, in contrast, occurs after sensitization with immunogenic doses of allergens. Performing the protocol of tolerance induction resulted in robust LZT to allergens in B cell-deficient mice in vivo, indicating that B cells are not required for the induction and effector phase of LZT. However, CHS reactions in vivo were restricted in B cell-deficient mice as compared to wild-type (WT) mice. In contrast, analysis of hapten-specific T cell activation in vitro revealed a strong proliferative response of T cells derived from both WT and B cell-deficient sensitized mice. Similar to WT animals, T cells obtained from tolerized B cell-deficient mice produced a Tc2 cytokine pattern of LZT with high levels of IL-4 and IL-10, whereas sensitization of B cell-deficient mice resulted in the typical Tc1 cytokine profile of CHS. Adoptive transfer of CD8+ effector T cells from tolerized or sensitized B cell-deficient mice induced significant LZT or CHS reactions, respectively, in WT recipients, demonstrating that the development of hapten-specific effector CD8+ T cells of LZT and CHS is independent of B cells.

Anti-allergic activity of 18beta-glycyrrhetinic acid-3-O-beta-D-glucuronide

Glycyrrhizin (18beta-glycyrrhetinic acid-3-O-beta-D-glucuronopyranosyl-(1 --> 2)-beta-D-glucuronide, GL) was transformed to 18beta-glycyrrhetinic acid-3-O-beta-D-glucuronide (GAMG) by Streptococcus LJ-22. The antiallergic activities of GL and GAMG was measured using a RBL cell assay system and contact hypersensitivity model mice. GAMG exhibited anti-allergic activity with IC50 values of 0.28 mM. GAMG, which is sweeter than GL, and 18beta-glycyrrhetinic acid, which is a GAMG metabolite by human intestinal bacteria, also inhibited the passive cutaneous anaphylaxis and skin contact inflammation. In conclusion, GAMG may be useful as a new sweet food additive and an anti-allergic agent.

Impaired dendritic-cell homing in vivo in the absence of Wiskott-Aldrich syndrome protein

Regulated migration and spatial localization of dendritic cells (DCs) are critical events during the initiation of physiologic immune responses and maintenance of tolerance. Here we have used cells deficient in the Wiskott-Aldrich syndrome protein (WASp) to demonstrate the importance of dynamic remodeling of the actin cytoskeleton for these trafficking processes to occur in vitro and in vivo. On fibronectin-coated surfaces, WASp-null immature murine DCs exhibited defects both of attachment and detachment, resulting in impaired net translocation compared with normal cells. The chemokinetic response to CCL21, which is critical for normal lymphatic trafficking, was also abrogated in the absence of WASp. In vivo in both fluorescein isothiocyanate (FITC) and oxazolone contact hypersensitivity models, WASp-null Langerhans cell (LC) migration was compromised, as judged by exit from the skin as well as by homing to the draining lymph node (LN). Furthermore, following systemic challenge with lipopolysaccharide (LPS) or toxoplasma-derived antigen, WASp-null DCs showed incomplete redistribution to T-cell areas in the spleen. Instead, they were retained ectopically in the marginal zone. DC trafficking in vivo is therefore dependent on a normally regulated actin cytoskeleton, which performs an essential function during maintenance of physiologic immunity and when disturbed may contribute significantly to the immunopathology of Wiskott-Aldrich Syndrome.

Inhibitory Effects of the C-2 Epimeric Isomers of Tea Catechins on Mouse Type IV Allergy

The inhibitory effects of C-2 epimeric isomers of (-)-epigallocatechin-3-O-gallate (EGCG) and two O-methylated EGCG derivatives, (-)-epigallocatechin-3-O-(3-O-methyl)gallate (EGCG3''Me) and (-)-epigallocatechin-3-O-(4-O-methyl)gallate (EGCG4''Me), against oxazolone-induced type IV allergy in male mice were investigated. These compounds exhibited strong antiallergic effects by percutaneous administration at a dose of 0.13 mg/ear. The inhibition rates of (-)-gallocatechin-3-O-gallate (GCG), (-)-gallocatechin-3-O-(3-O-methyl)gallate (GCG3''Me), and (-)-gallocatechin-3-O-(4-O-methyl)gallate (GCG4''Me) on mouse type IV allergy were 52.1, 53.3, and 54.8%, respectively. However, the antiallergic effects were weaker than those of their corresponding original tea catechins (2R,3R type). The inhibition rates of those were 88.0, 73.2, and 77.6%, respectively. For all of the catechins tested, oral administration at a dose of 50 mg/kg body weight significantly suppressed the allergic symptoms. The inhibitory rates varied from 24.0 to 60.6%. No significant differences were observed between the effects of the epimers (2S,3R type) and their corresponding original catechins (2R,3R type). The antiallergic effects of tea catechins and their C-2 epimers observed in this study were dose-dependent. These results suggest that C-2 epimers of tea catechins, which are produced during heat processing at high temperatures, could be disadvantageous for the antiallergic effects on type IV allergy.

Melatonin blocks dexamethasone-induced immunosuppression in a seasonally breeding rodent Indian palm squirrel, Funambulus pennanti

In vivo effect of dexamethasone and melatonin on immunomodulation has been investigated by studying the lymphocyte proliferation to the mitogen Con A from various lymphoid tissues including bone marrow cells of a seasonally breeding rodent adult male F. pennanti during reproductively inactive phase (October to December). During this phase, animal faces the maximum challenges of the nature (hypothermic stress, scarcity of food and shelter). Dexamethasone treatment (60 microg/day/squirrel) for 60 consecutive days significantly decreased the thymus and spleen activity. The lymphoid tissues mass, total leukocyte, lymphocyte count of peripheral blood, bone marrow and T-cell mediated immune function was also significantly suppressed following the dexamethasone treatment but treatment of melatonin (25 microg/squirrel/day) along with dexamethasone significantly restored the suppressed immune status in squirrels. Further, histological study of the thymus showed profound changes in the cellularity with a depletion of thymocytes in the cortex region of thymic lobules and increased in connective tissues and spindle cells. Melatonin treatment alone increased thymocytes density in thymic cortex, clearly suggesting that melatonin counteracted the experimentally induced immune stress by dexamethasone. Therefore, in nature during reproductively inactive phase of the squirrel a high level of melatonin was noted, that is required to combat nature's stress, which might have increased the internal level of corticoids.

A critical temporal window for selectin-dependent CD4+ lymphocyte homing and initiation of late-phase inflammation in contact sensitivity

Contact sensitivity (CS) is an inflammatory disorder characterized by early and late phases of leukocyte recruitment. We used a noninvasive intravital microscopy technique allowing for the direct visualization of leukocyte rolling and adhesion on blood vessel endothelium. By blocking specific adhesion molecules, we elucidated the molecular mechanisms mediating early leukocyte recruitment to be E- and P-selectin and demonstrated that leukocyte recruitment in the late phase had a different adhesive profile (mainly α₄-integrin). Complete blockade of E- and P-selectin within the first 2 h of leukocyte–endothelial cell interactions (but not later) eliminated selectin-independent leukocyte recruitment at 24 h. Despite the predominance of neutrophils in the early phase, specific elimination of CD4⁺ lymphocytes in the early phase eliminated the late response. CD4⁺ lymphocytes homed to skin via E- and P-selectin within the early phase and induced the late phase response. Addition of these same CD4⁺ lymphocytes 2 h after antigen challenge was too late for these cells to home to the skin and induce late phase responses. Our data clearly demonstrate that the antigen-challenged microenvironment is only accessible to CD4⁺ lymphocytes for the first 2 h, and that this process is essential for the subsequent recruitment of other leukocyte populations in late phase responses.

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.

Regulatory effects of osteoprotegerin on cellular and humoral immune responses

The interaction between receptor activator of nuclear factor-kappaB ligand (RANKL) and RANK has been reported to regulate immunity in addition to bone metabolism. The aim of this study was to determine if osteoprotegerin (OPG), an inhibitor of the RANKL-RANK interaction and possibly a new drug against osteoporosis, would adversely affect immunity. OPG was used to treat mice developing different models of cellular and humoral immune responses and also in vitro in T and B cell assays. In mice, OPG does not affect cell-mediated reactions such as contact hypersensitivity to the hapten oxazolone and liver damage, granuloma formation, and infectious load induced by mycobacterial infection. However, OPG increases humoral reactions such as the production of IgM, IgG, and IgE against the T cell dependent antigen keyhole limpet hemocyanin and the production of IgM against the T cell independent antigen Pneumovax. In vitro, OPG modestly co-stimulates T cells but does not affect the proliferation of B cells. OPG has modest immunoregulatory effects that seem to be confined to the humoral response to specific antigens.

Generation and function of reactive oxygen species in dendritic cells during antigen presentation

Although reactive oxygen species (ROS) have long been considered to play pathogenic roles in various disorders, this classic view is now being challenged by the recent discovery of their physiological roles in cellular signaling. To determine the immunological consequence of pharmacological disruption of endogenous redox regulation, we used a selenium-containing antioxidant compound ebselen known to modulate both thioredoxin and glutaredoxin pathways. Ebselen at 5-20 micro M inhibited Con A-induced proliferation and cytokine production by the HDK-1 T cell line as well as the LPS-triggered cytokine production by XS52 dendritic cell (DC) line. Working with the in vitro-reconstituted Ag presentation system composed of bone marrow-derived DC, CD4(+) T cells purified from DO11.10 TCR-transgenic mice and OVA peptide (serving as Ag), we observed that 1) both T cells and DC elevate intracellular oxidation states upon Ag-specific interaction; 2) ebselen significantly inhibits ROS production in both populations; and 3) ebselen at 5-20 micro M inhibits DC-induced proliferation and cytokine production by T cells as well as T cell-induced cytokine production by DC. Thus, Ag-specific, bidirectional DC-T cell communication can be blocked by interfering with the redox regulation pathways. Allergic contact hypersensitivity responses in BALB/c mice to oxazolone, but not irritant contact hypersensitivity responses to croton oil, were suppressed significantly by postchallenge treatment with oral administrations of ebselen (100 mg/kg per day). These results provide both conceptual and technical frameworks for studying ROS-dependent regulation of DC-T cell communication during Ag presentation and for testing the potential utility of antioxidants for the treatment of immunological disease.

Comparative study on the effects of ointments of tinidazole, hydrocortisone and clobetasol on animal models for inflammatory dermatitis in mice

To understand further the possible clinical effects of tinidazole ointment at relatively high concentration (2%) for atopic dermatitis (AD), we performed a comparative study with readily available topical corticosteroids, clobetasol propionate (0.005 or 0.05%) and hydrocorotisone butyrate (0.1%) (hereafter referred as clobetasol and hydrocortisone, respectively), on inflammatory dermatitis in mice. We also observed the effects of combined application of tinidazole with clobetasol (0.005%, one tenth of the clinical use) in comparison with tinidazole itself, clobetasol (0.05%) or hydrocortisone (0.1%) on the animal model. All ointments suppressed inflammatory dermatitis induced by trinitrochlorobenzen (TNCB) or oxazolone. The rank order of the potency to suppress the ear edema was clobetasol (0.05%), tinidazole (2%) with clobetasol (0.005%) > clobetasol (0.005%) > tinidazole (2%) in TNCB-induced dermatitis, and hydrocortisone (0.1%), clobetasol (0.05%) > tinidazole (2%), tinidazole with clobetasol (0.005%) > clobetasol (0.005%) in case of oxazolone-induced dermatitis. We confirmed that tinidazole (2%) suppresses immediate and late phase reactions in mice passively sensitized with anti-DNP IgE Mab. In addition, tinidazole (2%) was much more potent than hydrocortisone (0.1%) in suppressing the amount of scratching, presumably due to itching, in passively sensitized mice. These results indicate that the advantage of using ointments of tinidazole would be that it has stronger anti-itching effects than corticosteroids.

Non-genetic inheritable potential of maternal antibodies

Maternal antibodies (IgG and IgA) not only provide passive protection against microbial infections, but also exert a variety of equally important active, idiotypically-mediated immunoregulatory functions. Since the generation of maternal antibodies depends entirely on the stimulation of the mother's immune system by external mainly thymus-dependent antigens, with long-lived antigen independent plasma cells in the bone marrow, maternal antibodies represent the mother's collective ontogenetic immunological experience. Although their stimulatory potential in mice is restricted to the neonatal imprinting period, maternal antibodies exert a life-long determinative influence which is even dominant over seemingly genetic predispositions. Therefore, the functional impact of maternal IgG antibodies appears phenotypically as a non-genetic inheritance.

Role of Fas/Fas ligand-mediated apoptosis in murine contact hypersensitivity

Apoptosis plays an important role in immune responses, but little is known about its involvement in contact hypersensitivity (CH). In this study, we have investigated the role of Fas/Fas ligand (FasL)-mediated apoptosis in the pathogenesis of CH. Mice were sensitized by one topical application of 100 microl of 3% oxazolone to shaved skin of the abdomen. Six days later, CH was provoked by challenging both sides of sensitized mouse right ear with 15 microl of 1% oxazolone. Using a DNA ladder assay, we found that apoptosis was induced in the skin of oxazolone-sensitized mice 24-96 h after allergen challenge. Annexin V-fluorescein isothiocyanate (FITC)-propidium iodide (PI) apoptosis flow cytometric assay showed that early apoptotic CD4(+) T cells (annexin V-FITC(+)PI(-)), but not late apoptotic CD4(+) T cells (annexin V-FITC(+)PI(+)), increased in the inflamed skin of mice with CH. Moreover, the expressions of mRNAs for T helper (Th2) cytokine (interleukin (IL)-4), Th1 cytokine (interferon (IFN)-gamma) and proapoptotic molecules (Bax, Fas, FasL and IL-1beta-converting enzyme (ICE)/caspase-1) were significantly elevated in the oxazolone-sensitized mouse skin 6-72 h after allergen challenge. Dramatic increase in IL-10 mRNA was only observed in the sensitized mouse skin 6 and 12 h after allergen challenge. Furthermore, CH was significantly inhibited with decreased apoptosis and early apoptotic CD4(+) T cells in inflamed skin in Fas mutant lpr/lpr mice compared to wild-type mice, whereas there were no significant differences in IL-4, IFN-gamma, IL-10, Bax and ICE mRNAs in the inflamed skin of CH between lpr/lpr and wild-type mice. Our results thus suggest that Fas/FasL pathway partially contributes to apoptosis in murine CH and that Fas/FasL-mediated apoptosis plays a partial role in the development of CH. The contribution of Fas/FasL-mediated apoptosis to CH appears independent of Th1 and Th2 cytokines.

Genistein as an anti-inflammatory agent

OBJECTIVE AND DESIGN

The aim of this study was to investigate the impact of the isoflavone genistein on in vivo cell-mediated responses. In addition, we wanted to study the influence of genistein on collagen induced arthritis (CIA) in mice.

METHODS

Delayed type hypersensitivity reaction (DTH) to oxazolone and the inflammatory response to olive oil were measured in mice treated with genistein. In addition, the impact of genistein treatment on disease progression and outcome of collagen induced arthritis (CIA) was examined.

RESULTS

The DTH reaction to oxazolone and the granulocyte-mediated response were significantly suppressed in genistein-treated as compared to control mice. Also, genistein treatment led to decreased levels of oxazolone-specific antibodies. Histologically, mice exposed to genistein and immunized with collagen II displayed somewhat lower degree of inflammation and joint destruction. In addition, serum levels of autoantibodies to collagen II were significantly lower following genistein-treatment in immunized mice.

CONCLUSION

We conclude that genistein exerts evident anti-inflammatory properties affecting granulocytes, monocytes, and lymphocytes.

Why are there so few key mutant clones? The influence of stochastic selection and blocking on affinity maturation in the germinal center

A small number of key somatic mutations lead to high-affinity binding in the anti-hapten immune responses to 2-phenyl-5-oxazolone (phOx) and (4-hydroxy-3-nitrophenyl)acetyl (NP). Affinity maturation models of the germinal center hold that B cells carrying these key mutations are preferentially selected for expansion within the germinal centers. However, additional factors are required to account for some quantitative aspects of affinity maturation in vivo. Radmacher et al. have shown that key mutants are observed in vivo significantly less frequently than expected by these models. To account for this finding, they propose that selection is a stochastic process where key mutants may be overlooked by positive selection or recruited out of the germinal center. While acknowledging that a minimal amount of stochastic selection is probably unavoidable in the germinal center, we instead propose a structural explanation for this key mutant discrepancy. This model is based on the existence of a large number of blocking mutations whose presence can prevent the ability of key mutations to confer high-affinity binding. Using mathematical modeling and computer simulation, we show that in addition to reconciling the key mutant discrepancy, the blocking model accounts for other aspects of experimental data that are not predicted by the stochastic selection model. In particular, the blocking model is consistent with the observation that key mutants generally exhibit a higher number of mutations per sequence in the phOx response, but a lower number in the NP response.

Impaired contact hypersensitivity in macrophage migration inhibitory factor-deficient mice

To determine whether macrophage migration inhibitory factor (MIF) is required for contact hypersensitivity (CHS) response, MIF-deficient (MIF KO) and wild-type (WT) mice were sensitized with trinitrochlorobenzene (TNCB) or oxazolone on their abdominal skin and challenged on the dorsum skin of one ear 5 days later. Significant ear swelling was observed in the WT mice, but this response was inhibited in the MIF KO mice (p<0.01 for MIF KO vs. WT mice in 24 h). In addition, lymph node cells from hapten-sensitized MIF KO mice showed a decreased capacity for transferring the CHS response. A topical application of TNCB (200 microg) caused a significant decline in epidermal Langerhans cell (LC) density (20.3%; p<0.01 compared with vehicle) 4 h after application in WT mice, but it failed to provoke a significant epidermal LC migration in MIF KO mice (7.4%). By mixed lymphocyte reaction, the T cell proliferative response to alloantigen was significantly decreased in the MIF KO mice compared with WT mice (p<0.005). Taken together, these results indicate that MIF is pivotal in the regulation of cutaneous immune responses and plays a central role in LC migration and T cell proliferation for the CHS response.

L-selectin or ICAM-1 deficiency reduces an immediate-type hypersensitivity response by preventing mast cell recruitment in repeated elicitation of contact hypersensitivity

Repeated Ag exposure results in a shift in the time course of contact hypersensitivity (CH) from a typical delayed-type to an immediate-type response followed by a late phase reaction. Chronic CH responses are clinically relevant to human skin allergic diseases, such as atopic dermatitis, that are usually caused by repeated stimulation with environmental Ags. Chronic inflammatory responses result in part from infiltrating leukocytes. To determine the role of leukocyte adhesion molecules in chronic inflammation, chronic CH responses were assessed in mice lacking L-selectin, ICAM-1, or both adhesion molecules. Following repeated hapten sensitization for 24 days at 2-day intervals, wild-type littermates developed an immediate-type response at 30 min after elicitation, followed by a late phase reaction. By contrast, loss of ICAM-1, L-selectin, or both, eliminated the immediate-type response and inhibited the late phase reaction. Similar results were obtained when wild-type littermates repeatedly exposed to hapten for 22 days were treated with mAbs to L-selectin and/or ICAM-1 before the elicitation on day 24. The lack of an immediate-type response on day 24 paralleled a lack of mast cell accumulation after 30 min of elicitation and decreased serum IgE production. Repeated Ag exposure in wild-type littermates resulted in increased levels of serum L-selectin, a finding also observed in atopic dermatitis patients. The current study demonstrates that L-selectin and ICAM-1 cooperatively regulate the induction of the immediate-type response by mediating mast cell accumulation into inflammatory sites and suggests that L-selectin and ICAM-1 are potential therapeutic targets for regulating human allergic reactions.

Investigations into the immunomodulatory activity of Argyreia speciosa

The objective of the present study was to investigate the immunomodulatory activity of Argyreia speciosa on cellular and humoral immunity. Oral administration of the ethanolic extract of A. speciosa root (ASEE), at the doses of 50, 100 and 200 mg/kg in mice, dose-dependently potentiated the delayed-type hypersensitivity reaction induced both by sheep red blood cells (SRBC) and oxazolone. It significantly enhanced the production of circulating antibody titre in mice in response to SRBC. ASEE failed to show any effect on macrophage phagocytosis. Chronic administration of ASEE significantly ameliorated the total white blood cell count and also restored the myelosuppressive effects induced by cyclophosphamide. The present investigation reveals that ASEE possesses immunomodulatory activity.

Contribution of Langerhans cell-derived IL-18 to contact hypersensitivity

The epidermal Langerhans cells (LC), a member of the dendritic cell family, and the LC-derived cytokine IL-12 play a pivotal role in the initiation of contact hypersensitivity (CHS), a Th1 immune response in the skin. Because IL-18, another LC-derived cytokine, shares functional and biological properties with IL-12, we examined a potential role for IL-18 in CHS initiation. Our studies demonstrated that during the induction phase of murine CHS, IL-18 mRNA was significantly up-regulated in the skin-draining lymph nodes (LN). Migratory hapten-modified LC in LN expressed high levels of IL-18 mRNA and secreted functional IL-18 protein. LN cells produced significant amounts of IFN-gamma following in vitro IL-12 stimulation, which could be partially blocked by anti-IL-18 Ab, suggesting a synergistic role for endogenous IL-18 in IFN-gamma production by LN cells. Because mature IL-18 requires cleavage of immature precursors by caspase-1, we further examined IL-12-induced IFN-gamma production in caspase-1(-/-) LN cells. An impaired IFN-gamma production was seen in caspase-1(-/-) LN cells, which could be restored by addition of exogenous IL-18, supporting a role for caspase-1-cleaved, mature IL-18 in IFN-gamma production. Finally, in vivo studies showed that CHS responses were significantly inhibited in mice treated with neutralizing IL-18 Ab as well as in caspase-1(-/-) mice deficient in mature IL-18, indicating functional relevance for IL-18 in CHS. Taken together, our studies demonstrate that LC-derived IL-18 significantly contributes to CHS initiation.

The selective triggering of CD40 on keratinocytes in vivo enhances cell-mediated immunity

CD40 is expressed on a wide array of hematopoietic and non-hematopoietic cells, including keratinocytes. The pivotal in vivo function of CD40 on hematopoietic cells in the regulation of both humoral and cell-mediated immunity is well established. However, whether CD40 expression on non-hematopoietic cells influences immunity has until now not been addressed. Therefore, we transgenically expressed human CD40 (hCD40) under the control of the keratin 14 promoter to drive expression of hCD40 in basal keratinocytes of mice. When we selectively engaged hCD40 in vivo on the keratinocytes of these mice, the keratinocytes secreted TNF-alpha, resulting in dendritic cell migration to draining lymph nodes and enhanced in vitro T cell priming to an epicutaneously applied chemical sensitizer. Exclusive CD40 engagement on keratinocytes during a contact hypersensitivity response displayed exacerbated and prolonged cutaneous immune reactions relative to control mice. Thus, CD40 engagement on non-hematopoietic cells, such as keratinocytes, can amplify cutaneous and regional T cell responses in vivo.

Mechanism of action of combined short-term CTLA4Ig and anti-CD40 ligand in murine systemic lupus erythematosus

Short-term combination therapy with the costimulatory antagonists CTLA4Ig and anti-CD40 ligand induces prolonged suppression of disease onset in New Zealand Black/New Zealand White F(1) systemic lupus erythematosus-prone mice. To determine the mechanism for this effect, 20- to 22-wk-old New Zealand Black/New Zealand White F(1) mice were treated with six doses each of CTLA4Ig and anti-CD40 ligand Ab over 2 wk. Combination-treated mice, but not mice treated with either agent alone, had prolonged survival and the production of pathogenic IgG anti-dsDNA Ab was suppressed. Twenty weeks after completion of treatment the frequency of activated B cells producing anti-dsDNA Ab was decreased, and the abnormal transition of T cells from the naive to the memory compartment was blocked. Combination treatment partially suppressed class switching and decreased the frequency of somatic mutations in the V(H)BW-16 gene, which is expressed by pathogenic anti-DNA Abs. Treated mice were still able to respond to the hapten oxazolone when it was given 8 wk after treatment initiation, and they mounted a somatically mutated IgG anti-oxazolone response that was noncross-reactive with dsDNA. Fifty to 60% of previously treated mice, but only 14% of previously untreated mice, responded within 2-3 wk to a second course of therapy given at the onset of fixed proteinuria and remained well for a further 3-4 mo. Although this treatment had no immediate effect on serum anti-dsDNA Abs or on the abnormal T cell activation observed in sick mice, 25% of treated mice lived for >18 mo compared with 5% of untreated controls. These results suggest that the effect of costimulatory blockade in remission induction must be mediated by a different mechanism than is demonstrated in the disease prevention studies.

Increased and prolonged inflammation and angiogenesis in delayed-type hypersensitivity reactions elicited in the skin of thrombospondin-2--deficient mice

Angiogenesis and enhanced microvascular permeability are hallmarks of a large number of inflammatory diseases. Although up-regulation of proangiogenic factors such as vascular endothelial growth factor and interleukin-8 have been previously reported in inflamed tissue, the biologic role of endogenous inhibitors of angiogenesis in inflammation has remained unclear. To investigate the biologic role of the potent angiogenesis inhibitor thrombospondin-2 (TSP-2) in the control of cutaneous inflammation, delayed-type hypersensitivity reactions were elicited in the ear skin of wild-type and TSP-2-deficient mice by topical sensitization and challenge with oxazolone. Cutaneous TSP-2 expression was up-regulated in the inflamed skin of wild-type mice, predominantly in dermal fibroblasts and microvessels. Lack of TSP-2 resulted in a significantly enhanced inflammatory response with increased angiogenesis, edema formation, and inflammatory infiltration. Ear swelling and inflammation persisted for more than 2 weeks in TSP-2-deficient mice, as compared with 1 week in wild-type mice. Although baseline vascular permeability was unchanged, significantly enhanced microvascular leakage was found in the inflamed skin of TSP-2-deficient mice. Moreover, the fraction of rolling leukocytes was significantly increased in the untreated skin of TSP-2-deficient mice. These results reveal an important role of TSP-2 in limiting the extent and the duration of edema formation, angiogenesis, and inflammatory cell infiltration during acute and chronic inflammation.

Biochemical changes in the efferent lymph plasma after oxazolone stimulation

The lymph node is a specialized microenvironment for the regulation of immune responses. The reticular network of the lymph node provides a structure that facilitates not only intercellular interactions, but the intranodal flow of lymph fluid. To assess biochemical changes in the nodal lymph plasma after antigen stimulation, prescapular lymph nodes in sheep were stimulated with the epicutaneous antigen oxazolone. The efferent lymph from both antigen-stimulated and contralateral control prescapular lymph nodes was continuously monitored for more than 120 h. The oxazolone-stimulated lymph plasma was associated with a selective increase in cholesterol content during the 'recruitment' phase of lymph node enlargement. The peak in cholesterol was followed closely by a significant increase in lymph plasma LDH concentration. In contrast, there was no significant difference between oxazolone-stimulated and control lymph plasma in the concentration of triglycerides, albumin, alkaline phosphatase, and alanine transferase. These selective biochemical changes in the efferent lymph appeared to reflect the dynamics of lymphocyte activation within the lymph node as well as provide a practical measure of the lymph node response to antigen stimulation.

Topical peroxisome proliferator activated receptor-alpha activators reduce inflammation in irritant and allergic contact dermatitis models

Activators of peroxisome proliferator activated receptor-alpha, a nuclear hormone receptor that heterodimerizes with retinoid X receptor, stimulate epidermal differentiation and inhibit proliferation. Here we determined the anti-inflammatory effects of peroxisome proliferator activated receptor-alpha agonists in models of irritant and allergic contact dermatitis produced in mouse ears by topical treatment with 12-O-tetradecanoylphorbol-13-acetate and oxazalone, respectively. As expected, 12-O-tetradecanoylphorbol-13-acetate treatment resulted in a marked increase in the thickness and weight of the ears and provoked an inflammatory cell infiltrate in the dermis. Topical treatment with three different peroxisome proliferator activated receptor-alpha agonists, clofibrate, WY 14643, or linoleic acid, 45 min and 4 h after 12-O-tetradecanoylphorbol-13-acetate application, resulted in a marked decrease in ear thickness and weight and a reduction in the number of inflammatory cells in the dermis. The reduction in inflammation by these peroxisome proliferator activated receptor-alpha agonists was of similar magnitude to that seen with a potent topical glucocorticoid, clobetasol. In contrast, stearic acid, a free fatty acid that does not activate peroxisome proliferator activated receptor-alpha, had no effect on the 12-O-tetradecanoylphorbol-13-acetate-induced inflammation. Moreover, clofibrate did not significantly alter ear thickness following 12-O-tetradecanoylphorbol-13-acetate treatment in peroxisome proliferator activated receptor-alpha-/- mice, indicating that the anti-inflammatory effect is mediated by peroxisome proliferator activated receptor-alpha. As tumor necrosis factor-alpha and interleukin-1alpha are major mediators of cutaneous inflammation we next used immunohistochemistry to determine whether the peroxisome proliferator activated receptor-alpha agonists reduce the levels of these cytokines in 12-O-tetradecanoylphorbol-13-acetate-treated skin. 12-O-tetradecanoylphorbol-13-acetate treatment resulted in an increase in tumor necrosis factor and interleukin-1alpha staining in the epidermis that was reduced by clofibrate treatment. Finally, clofibrate treatment also reduced ear thickness and weight in oxazalone-induced allergic dermatitis, a change that was accompanied by a reduction in inflammatory cells in the dermis and a decrease in tumor necrosis factor-alpha and interleukin-1alpha levels in the oxazalone-treated epidermis. These studies demonstrate that topically applied peroxisome proliferator activated receptor-alpha agonists possess receptor mediated, anti-inflammatory activity in both irritant and allergic contact dermatitis animal models. The anti-inflammatory properties of peroxisome proliferator activated receptor-alpha agonists, coupled with their anti-proliferative and pro-differentiating effects, suggest that they could be beneficial for the treatment of a variety of cutaneous diseases.

Focal topographic changes in inflammatory microcirculation associated with lymphocyte slowing and transmigration

Microcirculation is the primary mechanism for delivering lymphocytes to inflammatory tissues. Blood flow within microvessels ensures a supply of lymphocytes at the blood-endothelial interface. Whether the structure of the inflammatory microcirculation facilitates lymphocyte transmigration is less clear. To illuminate the microcirculatory changes associated with lymphocyte transmigration, we used intravital videomicroscopy to examine the dermal microcirculation after application of the epicutaneous antigen oxazolone. Intravascular injection of fluorescein-labeled dextran demonstrated focal topographic changes in the microcirculation. These focal changes had the appearance of loops or hairpin turns in the oxazolone-stimulated skin. Changes were maximal at 96 h and coincided with peak lymphocyte recruitment. To determine whether these changes were associated with lymphocyte transmigration, lymphocytes obtained from efferent lymph of draining lymph nodes at 96 h were fluorescently labeled and reinjected into inflammatory microcirculation. Epifuorescence intravital video microscopy demonstrated focal areas were associated with lymphocyte slowing and occasional transmigration. In contrast, focal loops and lymphocyte slowing were rarely observed in the contralateral control microcirculation. Results suggest that structural adaptations in inflammatory microcirculation represented by focal topographic changes may contribute to regulation of tissue entry by recirculating lymphocytes.

Hapten-specific tolerance induced by acute, low-dose ultraviolet B radiation of skin requires mast cell degranulation

The deleterious effects of ultraviolet B radiation (UVR) on cutaneous immunity are mediated in part by cytokines released from cutaneous cells following radiation exposure. On the one hand, TNF-alpha has been advocated as the primary mediator of failed contact hypersensitivity induction, and, on the other hand, IL-10 has been held responsible for tolerance. While keratinocytes exposed to UVR have been found to produce both TNF-alpha and IL-10, there is reason to question whether these major cellular constituents of the epidermis are the relevant source of immunomodulatory cytokines after UVR. Dermal mast cells also produce TNF-alpha and IL-10, and we have recently reported that mast cell-derived TNF-alpha is required for UVR-induced impairment of CH induction. In this study, we have examined whether mast cells are also a relevant source of IL-10 in UVR-dependent tolerance. We found that (a) UVR fails to induce tolerance in mast cell-deficient mice, and (b) that tolerance occurs if mast cells are triggered to degranulate after ligation of the IgE receptor. Both types of tolerance were neutralized with anti-IL-10 antibodies, are hapten specific, and are associated with regulatory lymphoid cells. We conclude that mast cells are required in UVR-induced tolerance and may be one of the major sources of IL-10 that mediates the tolerance induced by acute, low-dose UVR.

Stimulatory effects of B7-related protein-1 on cellular and humoral immune responses in mice

Inducible costimulator (ICOS) and B7-related protein-1 (B7RP-1) constitute a receptor-ligand pair involved in T cell costimulation. In this study, the stimulatory effects of B7RP-1 on cellular and humoral immune responses were investigated giving mice a construct with the extracellular domain of murine B7RP-1 fused with human IgG1 Fc (B7RP-1-Fc). B7RP-1-Fc stimulated contact hypersensitivity (CH) given near either the time of sensitization or challenge with oxazolone. When given near challenge time, B7RP-1-Fc stimulated CH more than a construct containing the extracellular domain of murine B7.2 and Fc (B7.2-Fc). B7RP-1-Fc increased the number of cells in lymph nodes draining the skin sensitized with oxazolone, especially activated T cells. B7RP-1-Fc also increased the ability of the cells in these lymph nodes to induce CH when transfused into naive mice. B7RP-1-Fc stimulated the production of anti-keyhole limpet hemocyanin (KLH) Ab, increasing anti-KLH IgG, IgG2a, and IgE, whereas B7.2-Fc did not affect this production. B7RP-1-Fc also increased the number of cells in lymph nodes draining the skin immunized with KLH and their production of IFN-gamma, IL-4, and IL-10 in response to KLH. Finally, B7RP-1-Fc increased the presence of eosinophils in the bronchoalveolar lavage and lungs of mice sensitized and challenged with OVA so to mount an asthmatic reaction. B7RP-1-Fc stimulates both cellular and humoral immune responses in vivo by increasing number and function of T and B cells reacting to Ag exposure.

Interleukin (IL)-18 induces Langerhans cell migration by a tumour necrosis factor-alpha- and IL-1beta-dependent mechanism

Following skin sensitization a proportion of epidermal Langerhans cells (LC) are stimulated to leave the skin and to migrate, via afferent lymphatics, to draining lymph nodes where they accumulate as immunostimulatory dendritic cells (DC). It has been demonstrated previously that tumour necrosis factor-alpha (TNF-alpha), an inducible product of epidermal keratinocytes, and interleukin (IL)-1beta, produced exclusively by LC in murine epidermis, provide important signals for the initiation of this response. Recently, it has been demonstrated that IL-18, a cytokine produced by both LC and keratinocytes within the epidermis, may also participate in immune responses induced following skin sensitization. In the present investigations, the ability of IL-18 to contribute to the regulation of LC migration and the accumulation of DC in draining lymph nodes has been examined. It was found that, like IL-1beta, IL-18 administered intradermally to mice resulted in a significant reduction in epidermal major histocompatibility complex (MHC) class II+ LC densities and a marked increase in lymph node DC numbers. Using neutralizing anti-TNF-alpha and blocking anti-type I IL-1 receptor (IL-1RI) antibodies, it was shown also that the induction by IL-18 of both LC mobilization and DC accumulation in regional lymph nodes was dependent upon availability of TNF-alpha and the integrity of IL-1RI signalling. Furthermore, using IL-1beta converting enzyme (caspase-1) knockout mice, IL-18-induced LC migration was found to have a mandatory requirement for active IL-1beta. Importantly, not only was IL-18 able to contribute to the regulation of LC migration, it was found to be essential for the manifestation of these processes in response to topical sensitization with the contact allergen oxazolone.

Signals that initiate somatic hypermutation of B cells in vitro

Somatic hypermutation is initiated as B lymphocytes proliferate in germinal centers. The signals that switch on the mutation process are unknown. We have derived an in vitro system to define signals that will initiate mutation in normal, naive splenic B cells. We find that three signals are required to allow detection of somatic mutation in vitro; these are anti-Ig, anti-CD40, and anti-CD38. If any one of these is omitted, mutation remains off. We show that CD40 is obligatory in vivo, as CD40 knockout mice exhibit no Ag-driven mutation. In contrast, CD38 is not, as CD38 knockout mice mutate normally. We believe that, in vitro, CD38, in combination with other stimuli, drives extensive cell division, allowing the detection of mutated sequences. However, in germinal centers in vivo, proliferative activity is instigated by a different molecule. This is the first demonstration of the initiation of hypermutation in vitro with normal splenic B cells using defined stimuli.

Pineal modulation of thymus and immune function in a seasonally breeding tropical rodent, Funambulus pennanti

The immune system driven by cytokines is now known to be influenced by various other endocrine glands and its hormones. Results of the present study indicate a bidirectional relation between the pineal-thymus axis and the immune system status of an Indian tropical rodent, Funambulus pennanti, during winter months (reproductive inactive phase), when it faces maximum challenges from nature. Pinealectomy during the reproductive inactive phase inhibited thymus and spleen functions, which resulted in significant changes in leukocyte and lymphocyte counts and T-cell-mediated immune function (measured in terms of delayed-type hypersensitivity response to oxazolone). Blastogenic responses of lymphoid cells (thymocytes, splenocytes, and lymph node cells) also decreased following ablation of the pineal gland. To check the definite role of the pineal gland we injected melatonin into pinealectomized squirrels, and the suppressed immune function was significantly restored. Neuroendocrine control of the pineal gland on the histocompatible tissues in this seasonal breeder, F. pennanti, suggests an adaptive mechanism of the immune system for survival in the tropical zone. J. Exp. Zool. 289:90-98, 2001.

Stochastic regulation of cell migration from the efferent lymph to oxazolone-stimulated skin

The systemic immune response is a dynamic process involving the trafficking of lymphocytes from the Ag-stimulated lymph node to the peripheral tissue. Studies in sheep have demonstrated several phases of cell output in the efferent lymph after Ag stimulation. When skin contact sensitizers are used as Ag, the efferent lymph cell output peaks approximately 96 h after Ag stimulation and is temporally associated with the recruitment of cells into the skin. To investigate the relative contribution of this high-output phase of efferent lymphocytes to lymphocytic inflammation in the skin, we used a common contact sensitizer 2-phenyl-4-ethoxymethylene-5-oxazolone (oxazolone) to stimulate the skin and draining prescapular lymph node of adult sheep. The efferent lymph ducts draining the Ag-stimulated and contralateral control lymph nodes were cannulated throughout the experimental period. The lymphocytes leaving the lymph nodes during the 72-h period before maximum infiltration were differentially labeled with fluorescent tracers, reinjected into the arterial circulation, and tracked to the site of Ag stimulation. Quantitative tissue cytometry of the skin at the conclusion of the injection period (96 h after Ag stimulation) demonstrated more migratory cells derived from the Ag-stimulated lymph node than the contralateral control (median 18.5 vs 15.5 per field; p < 0.05). However, when corrected for total cell output of the lymph node, the Ag-stimulated migratory cells were 3.8-fold more prevalent in the skin than the contralateral control cells. These results suggest that the in situ immune response generally mirrors the frequency of recruitable lymphocytes in the peripheral blood.