Interferon-gamma inducible protein (IP-10) expression is mediated by CD8+ T cells and is regulated by CD4+ T cells during the elicitation of contact hypersensitivity

Dendritic Epidermal T Cells in Allergic Contact Dermatitis

Allergic contact dermatitis (ACD) is a common inflammatory skin disease with a prevalence of approximately 20% in the European population. ACD is caused by contact allergens that are reactive chemicals able to modify non-immunogenic self-proteins to become immunogenic proteins. The most frequent contact allergens are metals, fragrances, and preservatives. ACD clinically manifests as pruritic eczematous lesions, erythema, local papules, and oedema. ACD is a T cell-mediated disease, involving both CD4⁺ and CD8⁺ T cells. In addition, γδ T cells appear to play an important role in the immune response to contact allergens. However, it is debated whether γδ T cells act in a pro- or anti-inflammatory manner. A special subset of γδ T cells, named dendritic epidermal T cells (DETC), is found in the epidermis of mice and it plays an important role in immunosurveillance of the skin. DETC are essential in sensing the contact allergen-induced stressed environment. Thus, allergen-induced activation of DETC is partly mediated by numerous allergen-induced stress proteins expressed on the keratinocytes (KC). Several stress proteins, like mouse UL-16-binding protein-like transcript 1 (Mult-1), histocompatibility 60 (H60) and retinoic acid early inducible-1 (Rae-1) α-ε family in mice and major histocompatibility complex (MHC) class I-chain-related A (MICA) in humans, are upregulated on allergen-exposed KC. Allergen-induced stress proteins expressed on the KC are consequently recognized by NKG2D receptor on DETC. This review focuses on the role of γδ T cells in ACD, with DETC in the spotlight, and on the role of stress proteins in contact allergen-induced activation of DETC.

Cytokine Production in Mixed Cultures of Mesenchymal Stromal Cells from Wharton's Jelly and Peripheral Blood Lymphocytes

We compared the production of 19 humoral factors in mixed cultures of mesenchymal stromal cells from Wharton's jelly and allogenic peripheral blood lymphocytes. For evaluation of the specificity of immunosuppressive activity of mesenchymal stromal cells, comparative analysis of the production of these humoral factors in mixed cultures of lymphocytes and epithelial BxPC-3 cells was conducted. The production of soluble factors in both mono- and mixed cultures significantly correlated (p<0.05). The maximum production was found for proinflammatory chemokine IP-10 and IFN-γ and anti-inflammatory cytokine IL-10. The major difference of mesenchymal stromal cells from epithelial BxPC-3 cells was 7-fold higher production of IL-10, which can explain the immunosuppressive effect of mesenchymal stromal cells.

Leukotriene B₄-leukotriene B₄ receptor axis promotes oxazolone-induced contact dermatitis by directing skin homing of neutrophils and CD8⁺ T cells

Leukotriene B4 (LTB4 ) is a lipid mediator that is rapidly generated in inflammatory sites, and its functional receptor, BLT1, is mostly expressed on immune cells. Contact dermatitis is a common inflammatory skin disease characterized by skin oedema and abundant inflammatory infiltrates, primarily including neutrophils and CD8(+) T cells. The role of the LTB4 -BLT1 axis in contact dermatitis remains largely unknown. In this study, we found up-regulated gene expression of 5-lipoxygenase and leukotriene A4 hydrolase, two critical enzymes for LTB4 synthesis, BLT1 and elevated LTB4 levels in skin lesions of oxazolone (OXA)-induced contact dermatitis. BLT1 deficiency or blockade of LTB4 and BLT1 by the antagonists, bestatin and U-75302, respectively, in the elicitation phase caused significant decreases in ear swelling and skin-infiltrating neutrophils and CD8(+) T cells, which was accompanied by significantly reduced skin expression of CXCL1, CXCL2, interferon-γ and interleukin-1β. Furthermore, neutrophil depletion during the elicitation phase of OXA-induced contact dermatitis also caused significant decreases in ear swelling and CD8(+) T-cell infiltration accompanied by significantly decreased LTB4 synthesis and gene expression of CXCL2, interferon-γ and interleukin-1β. Importantly, subcutaneous injection of exogenous LTB4 restored the skin infiltration of CD8(+) T cells in neutrophil-depleted mice following OXA challenge. Collectively, our results demonstrate that the LTB4 -BLT1 axis contributes to OXA-induced contact dermatitis by mediating skin recruitment of neutrophils, which are a major source of LTB4 that sequentially direct CD8(+) T-cell homing to OXA-challenged skin. Hence, LTB4 and BLT1 could be potential therapeutic targets for the treatment of contact dermatitis.

Accumulation of metal-specific T cells in inflamed skin in a novel murine model of chromium-induced allergic contact dermatitis

Chromium (Cr) causes delayed-type hypersensitivity reactions possibly mediated by accumulating T cells into allergic inflamed skin, which are called irritants or allergic contact dermatitis. However, accumulating T cells during development of metal allergy are poorly characterized because a suitable animal model is not available. This study aimed to elucidate the skewing of T-cell receptor (TCR) repertoire and cytokine profiles in accumulated T cells in inflamed skin during elucidation of Cr allergy. A novel model of Cr allergy was induced by two sensitizations of Cr plus lipopolysaccharide solution into mouse groin followed by single Cr challenge into the footpad. TCR repertoires and nucleotide sequences of complementary determining region 3 were assessed in accumulated T cells from inflamed skin. Cytokine expression profiles and T-cell phenotypes were determined by qPCR. CD3+CD4+ T cells accumulated in allergic footpads and produced increased T helper 1 (Th1) type cytokines, Fas, and Fas ligand in the footpads after challenge, suggesting CD4+ Th1 cells locally expanded in response to Cr. Accumulated T cells included natural killer (NK) T cells and Cr-specific T cells with VA11-1/VB14-1 usage, suggesting metal-specific T cells driven by invariant NKT cells might contribute to the pathogenesis of Cr allergy.

Novel anti-inflammatory effects of repaglinide in rodent models of inflammation

BACKGROUND

Repaglinide is an FDA-approved treatment for type 2 diabetes mellitus. The anti-inflammatory effect of repaglinide in the absence of diabetes has not been reported previously. It is the objective of this set of studies to investigate the potential anti-inflammatory effects of repaglinide.

METHOD

The in vivo anti-inflammatory effects of repaglinide were studied in two different models of delay type hyperreactivity (DTH) response induced by sheep red blood cells (sRBC) and 2,5'-dinitrofluorobenzene (DNFB), and in two different rodent models of lipopolysaccharide (LPS) challenge.

RESULTS

In mice systemically sensitized with sRBC, which subsequently received a local injection of sRBC in the footpad, local swelling occurred within 24 h after challenge. Repaglinide was efficacious in attenuating this response. In an orthogonal DTH model using DNFB as the antigen, the animals received topical sensitization with DNFB on their shaved backs, followed by topical challenge on the left ears. Repaglinide efficaciously downregulated the resulting ear swelling response. In mice challenged systemically or intratracheally with LPS, repaglinide significantly decreased serum tumor necrosis factor α level and bronchial alveolar lavage fluid MCP-1 levels, respectively.

CONCLUSION

This set of data suggests novel anti-inflammatory effects of repaglinide in nondiabetic animals. However, the high dose required for an efficacious effect would make this application impractical in the clinic.

Dual functions of prostaglandin D2 in murine contact hypersensitivity via DP and CRTH2

Prostaglandin D2 (PGD2) exerts its effects through two distinct receptors: the chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) and the D prostanoid (DP) receptor. Our previous study demonstrated that CRTH2 mediates contact hypersensitivity (CHS) in mice. However, the function of DP receptor remains to be fully established. In this study, we examine the pathophysiological roles of PGD2 using DP-deficient (DP(-/-)) and CRTH2/DP-deficient (CRTH2(-/-)/DP(-/-)) mice to elucidate receptor-mediated PGD2 action in CHS. We observed profound exacerbation of CHS in DP(-/-) mice. CRTH2(-/-)/DP(-/-) mice showed similar exacerbation, but to a lesser extent. These symptoms were accompanied by increased production of interferon-γ and IL-17. The increase in IL-17 producing γδ T cells was marked and presumably contributed to the enhanced CHS. DP deficiency promoted the in vivo migration of dendritic cells to regional lymph nodes. A DP agonist added to DCs in vitro was able to inhibit production of IL-12 and IL-1β. Interestingly, production of IL-10 in dendritic cells was elevated via the DP pathway, but it was lowered by the CRTH2 pathway. Collectively, PGD2 signals through CRTH2 to mediate CHS inflammation, and conversely, DP signals to exert inhibitory effects on CHS. Thus, we report opposing functions for PGD2 that depend on receptor usage in allergic reactions.

A hassle a day may keep the pathogens away: The fight-or-flight stress response and the augmentation of immune function

Stress is known to suppress or dysregulate immune function and increase susceptibility to disease. Paradoxically, the short-term fight-or-flight stress response is one of nature's fundamental defense mechanisms that galvanizes the neuroendocrine, cardiovascular, and musculoskeletal systems into action to enable survival. Therefore, it is unlikely that short-term stress would suppress immune function at a time when it may be critically required for survival (e.g., in response to wounding and infection by a predator or aggressor). In fact, studies have shown that stress can enhance immune function under certain conditions. Several factors influence the direction (enhancing versus suppressive) of the effects of stress on immune function: (1) DURATION: acute or short-term stress experienced at the time of activation of an immune response enhances innate and adaptive immune responses. Chronic or long-term stress can suppress or dysregulate immune function. (2) Leukocyte distribution: compartments (e.g., skin), that are enriched with immune cells during acute stress show immuno-enhancement, while those that are depleted of leukocytes (e.g., blood), show immuno-suppression. (3) The differential effects of physiologic versus pharmacologic stress hormones: Endogenous hormones in physiological concentrations can have immuno-enhancing effects. Endogenous hormones at pharmacologic concentrations, and synthetic hormones, are immuno-suppressive. (4) Timing: immuno-enhancement is observed when acute stress is experienced during the early stages of an immune response while immuno-suppression may be observed at late stages. The type of immune response (protective, regulatory/inhibitory, or pathological) that is affected determines whether the effects of stress are ultimately beneficial or harmful for the organism. Arguments based on conservation of energy have been invoked to explain potential adaptive benefits of stress-induced immuno-suppression, but generally do not hold true because most mechanisms for immuno-suppression expend, rather than conserve, energy. We propose that it is important to study, and if possible, to clinically harness, the immuno-enhancing effects of the acute stress response that evolution has finely sculpted as a survival mechanism, just as we study its maladaptive ramifications (chronic stress) that evolution has yet to resolve.

Ultraviolet B suppresses immunity by inhibiting effector and memory T cells

Contact hypersensitivity is a T-cell-mediated response to a hapten. Exposing C57BL/6 mice to UV B radiation systemically suppresses both primary and secondary contact hypersensitivity responses. The effects of UVB on in vivo T-cell responses during UVB-induced immunosuppression are unknown. We show here that UVB exposure, before contact sensitization, inhibits the expansion of effector CD4+ and CD8+ T cells in skin-draining lymph nodes and reduces the number of CD4+ and IFN-gamma+ CD8+ T cells infiltrating challenged ear skin. In the absence of UVB, at 10 weeks after initial hapten exposure, the ear skin of sensitized mice was infiltrated by dermal effector memory CD8+ T cells at the site of challenge. However, if mice were previously exposed to UVB, this cell population was absent, suggesting an impaired development of peripheral memory T cells. This finding occurred in the absence of UVB-induced regulatory CD4+ T cells and did not involve prostaglandin E2, suggesting that the importance of these two factors in mediating or initiating UVB-induced immunosuppression is dependent on UVB dose. Together these data indicate that in vivo T-cell responses are prone to immunoregulation by UVB, including a novel effect on both the activated T-cell pool size and the development of memory T cells in peripheral compartments.

Effects of the tumor microenvironment on the efficacy of tumor immunotherapy

Cancer immunotherapy utilizes vaccines targeting tumor antigens or tumor endothelium to prevent or regress tumors. Many cancer vaccines are designed to induce antigen-specific effector T cells that migrate to the tumor site. In an optimal situation, the effector T cells penetrate the tumor, release their effector molecules, induce tumor cell death and tumor regression. However, the tumor microenvironment is frequently immunosuppressive and contributes to a state of immune ignorance, impacting on the vaccine's ability to break tolerance to tumor antigen/s. This review discusses the factors in the tumor microenvironment that can affect the efficacy of cancer vaccines. In particular, the review focuses on pathways leading to effector T cell penetration of tumors or the inhibition of this process.

Reduced 2,4-dinitro-1-fluorobenzene-induced contact hypersensitivity response in IL-15 receptor??-deficient mice correlates with diminished CCL5/RANTES and CXCL10/IP-10 expression

Using a model of 2,4-dinitro-1-fluorobenzene-induced contact hypersensitivity (CHS) we found that, as compared with wild-type mice, IL-15 receptor alpha chain (IL-15Ralpha)-deficient mice showed significantly less ear swelling. This decreased response was associated with diminished expression of CCL5/RANTES and CXCL10/IP-10, chemokines critical for effector cell recruitment, in the inflamed tissue. We determined that both the number of CD8(+) T cells infiltrating the affected skin and the production of CCL5/RANTES by antigen-stimulated CD8(+) T cells were decreased in IL-15Ralpha(-/-) mice. The lower levels of CXCL10/IP-10 suggested that the IL-15Ralpha(-/-) mice had reduced production of IFN-gamma, the primary inducer of CXCL10/IP-10, which was in fact the case. However, by contrast with CCL5/RANTES, the diminished levels of IFN-gamma were likely due to the decreased number of skin-infiltrating CD8(+) T cells, since IFN-gamma production by antigen-stimulated CD8(+) T cells was comparable between wild-type and IL-15Ralpha(-/-) mice. Our data suggest a positive, pro-inflammatory feedback loop involving CCL5/RANTES, IFN-gamma and CXCL10/IP-10 that underlies the CHS reaction and that is disrupted, likely primarily by a defect in CCL5/RANTES production, in mice lacking IL-15Ralpha, resulting in impaired leukocyte recruitment and inflammation. Moreover, it is particularly noteworthy that the defect in CCL5/RANTES expression in CD8(+) T cells is intrinsic to the absence of IL-15Ralpha, indicating that IL-15Ralpha is critical for CCL5/RANTES expression in CD8(+) T cells.

IFN‐γ and TNF‐α are involved in urushiol‐induced contact hypersensitivity in mice

Contact hypersensitivity (CHS) is a cutaneous T-cell-mediated immunological reaction to applied haptens. Activated antigen-specific T cells release several cytokines and chemokines followed by the recruitment of inflammatory cells and skin damage. CD8+ T cells and CD4+ T cells have been involved in the establishment of previously described CHS. In this study, we investigated the induction of CHS by urushiol in mice. Maximum swelling in mouse ears was elicited 24 h after challenge with urushiol on day 9 of sensitization. IFN-gamma, TNF-alpha and IFN-gamma-inducible protein 10 (IP-10) mRNA were expressed after challenge of the antigen in urushiol-sensitized mice, but not in unsensitized mice. IFN-gamma knockout (KO) mice and TNF-alpha KO mice failed to elicit CHS with urushiol. Contact hypersensitivity and expressions of IFN-gamma, TNF-alpha and IP-10 mRNA were markedly suppressed in CD4+ and CD8+ cell-depleted mice. These results suggest that IFN-gamma, TNF-alpha, and possibly IP-10, play a critical role in CHS induced by urushiol, depending on both CD4+ T cells and CD8+ T cells.

A novel role for neutrophils as a source of T cell-recruiting chemokines IP-10 and Mig during the DTH response to HSV-1 antigen

Analogous to CD4+ T cells, neutrophils are essential participants in delayed-type hypersensitivity (DTH) to Herpes simplex virus type 1 antigen. However, what role they play in this cellular immune response is unclear. The recent recognition that neutrophils are potent producers of chemokines led us to hypothesize that they may help recruit CD4+ effector T cells. In the present study, we show that neutrophil depletion was accompanied by a marked decrease in the numbers of CD4+ and CXC receptor 3+ (CXCR3+)-expressing cells migrating to the DTH site and a sharp drop in the levels of interferon-inducible protein 10 (IP-10) and monokine induced by IFN-gamma (Mig). Purified mouse neutrophils were stimulated directly by IFN-gamma to secrete these chemokines, and neutrophils at the DTH site expressed IP-10. IFN-gamma knockout mice, which manifested depressed ear-swelling following DTH challenge, made little IP-10 and no Mig. Reconstitution of these mice with IFN-gamma induced CXCR3 ligand synthesis. Depletion of neutrophils or CD4+ T cells but not CD8+ T cells markedly reduced IFN-gamma levels, suggesting the former were direct (or indirect) cellular sources of this cytokine. Collectively, our results support the hypothesis that neutrophil production of T cell-recruiting chemokines contributes to the regulation and amplification of the DTH response.

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

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

T Lymphocyte-Mediated Immune Responses to Chemical Haptens and Metal Ions: Implications for Allergic and Autoimmune Disease

Chemical haptens and metal ions interact with proteins and thereby become recognizable by T and B lymphocytes. They induce the production of proinflammatory cytokines and chemokines by various cell types due to triggering of innate immune responses. This is an important prerequisite for the activation of the adaptive immune system and the development of diseases like allergic contact dermatitis and adverse drug and autoimmune reactions. Our increasing knowledge about the molecular basis of hapten and metal ion recognition by T cells and about the pathomechanisms of contact hypersensitivity and chemical-induced autoimmune reactions allows concomitant progress in the development of modern strategies for immunotherapy and will hopefully enable more specific intervention in hapten- and metal ion-induced human diseases in the future.

HIGH EXPRESSION OF CHEMOKINE GENE AS A FAVORABLE PROGNOSTIC FACTOR IN RENAL CELL CARCINOMA

PURPOSE

The presence and potential role of chemokines in clinical tumors remain poorly understood. Chemokines are a large family of chemoattractant cytokines with several members that are also able to regulate angiogenesis. We hypothesized that chemokines may have an important role in regulating tumor growth in renal cell carcinoma (RCC). To begin to test this hypothesis chemokine gene expression and its influence on prognosis, cellular infiltration and angiogenesis in RCC were examined.

MATERIALS AND METHODS

A total of 51 patients with sporadic RCC were analyzed for the expression of the 7 chemokine genes interleukin-8, gamma-interferon inducible protein-10 (IP-10), monokine induced by gamma-interferon (MIG), macrophage chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and regulated and activated normal T cells excreted and secreted (RANTES) using semiquantitative reverse transcriptasepolymerase chain reaction. Lymphocyte infiltration and microvessel density were determined immunohistochemically by staining CD8 and CD34 cells, respectively.

RESULTS

: The expression of IP-10, MIG, MIP-1beta and RANTES was significantly increased in tumor compared to normal kidney tissues. The expression of IP-10, MIG and MIP-1beta showed an inverse correlation with tumor size. Stages 1 to 3 tumors expressing high levels of IP-10, MIG, MIP-1beta and RANTES did not recur after curative surgery. Intratumor expression of IP-10, MIG and MIP-1beta showed a positive correlation with the degree of CD8 cell infiltrating in the tumor and an inverse correlation with microvessel density.

CONCLUSIONS

These results suggest that IP-10, MIG and MIP-1beta are expressed at high levels in tumors that rarely recur after surgery. The antitumorigenic effect of IP-10, MIG and MIP-1beta may result from the recruitment of lymphocyte infiltration and/or inhibition of angiogenesis in RCC. The amplification of chemokine expression by immunotherapy or gene therapy may be a practical and effective strategy to promote tumor regression.

Essential role of p38 mitogen-activated protein kinase in contact hypersensitivity

The present study was designed to elucidate the role of p38 mitogen-activated protein kinase (p38) in the pathogenesis of inflammation, using a mouse contact hypersensitivity (CHS) model induced by 2,4-dinitro-1-fluorobenzene (DNFB). Ear swelling was induced by challenge with DNFB, accompanied by infiltration of mononuclear cells, neutrophils, and eosinophils and a marked increase in mRNA levels of cytokines such as interleukin (IL)-2, interferon (IFN)-gamma, IL-4, IL-5, IL-1beta, IL-18, and tumor necrosis factor-alpha in the challenged ear skin. Both ear swelling and the number of infiltrated cells in DNFB-challenged ear skin were significantly inhibited by treatment with SB202190, a p38 inhibitor. Furthermore, the DNFB-induced expression of all cytokines except IL-4 was significantly inhibited by treatment with SB202190. Ribonuclease protection assay revealed that the mRNA levels of chemokines such as IP-10 and MCP-1 in ear skin were markedly increased at 24 h after challenge with DNFB. The induction of these chemokines was significantly inhibited by treatment with SB202190. In p38alpha +/- mice, both ear swelling and infiltration of cells induced by DNFB were reduced compared with those in wild-type mice. However, induction of cytokines by DNFB was also observed in p38alpha +/- mice, although the induction of IFN-gamma, IL-5, and IL-18 was typically reduced compared with that in wild-type mice. Challenge with DNFB slightly induced IP-10 and MCP-1 mRNA in p38alpha +/- mice, with weaker signals than those in SB202190-treated wild-type mice. These results suggest that p38 plays a key role in CHS and is an important target for the treatment of CHS.

Dominant expression of CXCR3 is associated with induced expression of IP-10 at hapten-challenged sites of murine contact hypersensitivity: a possible role for interferon-gamma-producing CD8(+) T cells in IP-10 expression

Murine contact hypersensitivity is elicited as a consequence of immunologic reactions triggered by skin-applied antigen, interactions among Langerhans cells, T cells, keratinocytes and mast cells, and a variety of chemokines generated by cellular interactions. In this study, we sensitized and challenged BALB/c mice with hapten, dinitrofluorobenzene or picryl chloride, and examined the expressions of mRNA for chemokines and their receptors by reverse transcription-polymerase chain reaction in the skin of elicited earlobes. CXC chemokines, IP-10 and Mig, were transcribed 24-48 h after challenge. This was associated with the expression of their agonistic receptor CXCR3, while mRNA for TARC and MDC, and their receptor CCR4 were not detected. Since CXCR3 and CCR4 are expressed preferentially on types 1 (Th1/Tc1) and 2 (Th2) T cells, respectively, the results suggested that the former type of T cells predominantly infiltrate at the elicited sites. Immune lymph node cells of the sensitized mice also expressed mRNA for CXCR3 but not CCR4 with concomitant transcription of interferon-gamma (IFN-gamma) but not interleukin-4 subsequent to challenge. The percentage of lymph node CD8(+) T cells was increased from 16% in naive mice to 30-50% in hapten-challenged mice, and in the immune lymph nodes, CD8(+) cells were the major source of IFN-gamma compared to CD4(+) cells. Since IFN-gamma is known to stimulate keratinocytes to produce IP-10 and Mig, it is suggested that these IFN-gamma-producing CD8(+) T cells enhance the production of these chemokines, thereby functioning as not only the effector cells but also the cytokine source to sustain the challenge reaction.

IFN-gamma-inducible protein 10 (IP-10; CXCL10)-deficient mice reveal a role for IP-10 in effector T cell generation and trafficking

IFN-gamma-inducible protein 10 (IP-10, CXCL10), a chemokine secreted from cells stimulated with type I and II IFNs and LPS, is a chemoattractant for activated T cells. Expression of IP-10 is seen in many Th1-type inflammatory diseases, where it is thought to play an important role in recruiting activated T cells into sites of tissue inflammation. To determine the in vivo function of IP-10, we constructed an IP-10-deficient mouse (IP-10(-/-)) by targeted gene disruption. Immunological analysis revealed that IP-10(-/-) mice had impaired T cell responses. T cell proliferation to allogeneic and antigenic stimulation and IFN-gamma secretion in response to antigenic challenge were impaired in IP-10(-/-) mice. In addition, IP-10(-/-) mice exhibited an impaired contact hypersensitivity response, characterized by decreased ear swelling and reduced inflammatory cell infiltrates. T cells recovered from draining lymph nodes also had a decreased proliferative response to Ag restimulation. Furthermore, IP-10(-/-) mice infected with a neurotropic mouse hepatitis virus had an impaired ability to control viral replication in the brain. This was associated with decreased recruitment of CD4(+) and CD8(+) lymphocytes into the brain, reduced levels of IFN-gamma and the IFN-gamma-induced chemokines monokine induced by IFN-gamma (Mig, CXCL9) and IFN-inducible T cell alpha chemoattractant (I-TAC, CXCL11) in the brain, decreased numbers of virus-specific IFN-gamma-secreting CD8(+) cells in the spleen, and reduced levels of demyelination in the CNS. Taken together, our data suggest a role for IP-10 in both effector T cell generation and trafficking in vivo.

Skin inflammation during contact hypersensitivity is mediated by early recruitment of CD8+ T cytotoxic 1 cells inducing keratinocyte apoptosis

Contact hypersensitivity (CHS) is a T cell-mediated, Ag-specific skin inflammation induced by skin exposure to haptens in sensitized individuals. Th1/T cytotoxic 1 cells are effector cells of CHS, whereas Th2/T regulatory CD4(+) T cells have down-regulating properties. We have previously shown that CHS to 2,4-dinitrofluorobenzene is mediated by specific CD8(+) effector cells, whose cytolytic activity is mandatory for induction of skin inflammation. In this study, using immunohistochemistry and RT-PCR analysis, we show that CD8(+) T cells are rapidly recruited into the skin at the site of hapten challenge before the onset of clinical and histological signs of skin inflammation. This early CD8(+) T cell recruitment is concomitant with: 1) transient IFN-gamma mRNA expression suggesting local activation of effector cells; and 2) induction of keratinocyte (KC) apoptosis which gradually increased to a maximum at the peak of the CHS response. Alternatively, skin infiltration of CD4(+) T cells occurred later and coincided with the peak of the CHS reaction and the beginning of the resolution of skin inflammation. Mice deficient in CD8(+) T cells did not develop CHS, whereas mice deficient in CD4(+) T cells developed an enhanced inflammatory response with increased numbers of CD8(+) T cells recruited in the skin associated with massive KC apoptosis. These data show that CHS is due to the early and selective recruitment in the skin of CD8(+) T cytotoxic 1 effector cells responsible for KC apoptosis.

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

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

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

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

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

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

Subcutaneous or oral administration of rhIL-11 modulated the contact hypersensitivity response

Recombinant human interleukin 11 (rhIL-11) is a multifunctional cytokine with immunomodulatory activity on both T cells and macrophages. The effects of rhIL-11 in a murine model of contact hypersensitivity (CHS) response have been studied. The CHS response is a T cell-mediated response directed against chemically modified self-proteins following epidermal exposure to haptens. CHS is generated in two phases. The sensitization phase involves dermal dendritic cell recognition of haptenized proteins and antigen presentation. The effector phase involves T cell recognition and activation. In mice sensitized with oxazolone, CHS was induced by secondary challenge to the right ear and measured by ear swelling 24 h later. rhIL-11 significantly suppressed CHS as measured by ear swelling and tissue myeloperoxidase activity when injected subcutaneously for 5 days from the day of sensitization or when administered only on the day before and the day of challenge, but was not effective when administered prior to or on the day of sensitization. These results indicate that subcutaneously administered rhIL-11 may modulate the effector phase of CHS. Administration of rhIL-11 as an oral gavage prior to sensitization also reduced CHS. However oral administration of rhIL-11 after sensitization had no effect. These results suggest that orally and subcutaneously administered rhIL-11 may act through different mechanisms to affect CHS.

Early local generation of C5a initiates the elicitation of contact sensitivity by leading to early T cell recruitment

We have shown previously that an early complement C5-dependent cascade is required to recruit T cells to elicit 24-h contact sensitivity (CS) responses. In this paper, we have characterized molecular events of this early required cascade by biochemically analyzing extracts of mouse ears undergoing elicitation of CS. Chemotactic activity was found after local Ag challenge, in CS ear extracts early (by 1 h), in CS ear extracts late (through 24 h), in previously immunized mice, but not in ears of vehicle-immunized or non-immune-challenged mice. The early chemotactic activity at 2 h was likely caused by C5a, because it was neutralized in vitro by anti-C5a Ab, was inactive on C5aR-deficient (C5aR-/-) macrophages, and was absent in C5-deficient mice. The activity was present in T cell-deficient mice, but elaboration was Ag-specific. This T cell-independent, Ag-specific elaboration of C5a early in CS ear responses likely led to T cell recruitment, because subsequent local IFN-gamma mRNA and protein expression, as markers of T cell arrival and activation, began by 4 h after Ag challenge. In contrast to early C5a chemotactic activity, late chemotactic activity 24 h after Ag challenge was unaffected by anti-C5, was active on C5aR-/- macrophages, was T cell-dependent, and by ELISA appeared largely due to chemokines (macrophage-inflammatory protein-1alpha and -1beta, IFN-gamma-inducible protein-10, and monocyte chemoattractant protein-1). Importantly, early generation of C5a was required for T cell recruitment because C5aR-/- mice had absent 24-h CS. Taken together, these findings indicate an important linkage of C5a as a component of early activated innate immunity that is required for later elicitation of acquired T cell immunity, probably by facilitating the initial recruitment of T cells into the Ag-challenged local site in CS responses.

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.

Effect of Am-80, a retinoid derivative, on 2, 4-dinitrofluorobenzene-induced contact dermatitis in mice

Retinoids have many pharmacological activities, including anti-inflammatory action and antiangiogenesis, effected through the regulation of various gene transcriptions. In this study, we investigated the effect of Am-80, one of the retinoic acid derivatives, on hapten-induced contact hypersensitivity in BALB/c mice. After application of 2,4-dinitrofluorobenzene (DNFB) to the ears of the mice, severe contact hypersensitivity with marked infiltration of inflammatory cells and hypertrophy of the epidermis was caused. The thickness of the ears increased biphasically and reached a peak 3 and 24 h after the DNFB challenge. Am-80 significantly inhibited ear thickness in the late-(24 h), but not the early-phase (3 h) reaction in a dose-dependent manner. In a histopathological study, obvious depression of edema and infiltration of inflammatory cells was observed in the ears of mice treated with Am-80. Am-80 inhibited the levels of expression in mice ears of interferon-gamma (IFN-gamma) and interleukin-6 (IL-6), but not tumor necrosis factor-alpha (TNF-alpha) or interleukin-4 (IL-4). Furthermore, Am-80 inhibited the antigen-induced production of some cytokines, including IFN-gamma and IL-6, but not IL-4, in vitro. Therefore, Am-80 inhibited hapten-induced contact hypersensitivity through the direct inhibition of inflammatory cytokines such as IFN-gamma and IL-6.

Secretion of CXC chemokine IP-10 by peripheral blood mononuclear cells from healthy donors and breast cancer patients stimulated with HER-2 peptides

CXC chemokines play an important role in recruitment of T cells to the site of activation and regulation of angiogenesis. CXC chemokines are secreted by T cells stimulated with cytokines or by established cytotoxic T lymphocyte (CTL) lines at recognition of conventional antigen (Ag), but the activation requirements and the relationship of interferon-gamma (IFN-gamma) inducible protein (IP-10) secretion with IFN-gamma induction in lymphocytes are still unclear. We studied the induction of IP-10 from nonadherent peripheral blood mononuclear cells (PBMC) by IFN-gamma, interleukin-12 (IL-12), and the HER-2 peptide E75, which forms a CTL-defined antigen. We found that IFN-gamma alone was a weak inducer of IP-10 in these cells, whereas IL-12 was a significantly stronger inducer of IP-10. In the presence of IL-12, the tumor peptide E75 (HER-2, 369-377) was a stronger inducer of IP-10 than was IL-12 alone. E75 and its variants mutated at position 5 could also induce IP-10 in the absence of exogenous IL-12 or IFN-gamma. IP-10 induction by E75 required HLA-A2 presentation and B7-CD28 interactions and was partially inhibited by blocking of CD40-CD40L interactions. These results indicate that presentation of tumor peptides to peripheral T cells can induce a fast chemokine response, which in its early phase may be higher than the IFN-gamma response. This shows that the IP-10 response was independent of any early-phase IFN-gamma response in peripheral T cells. This may be important for understanding the regulation of the balance between chemoattractant chemokines (CC) and CXC chemokines by tumor Ag and may have implications for understanding the mechanisms of polarization of T cells and conditioning of antigen-presenting cells (APC) by tumor antigens.

Different role of IL-4 in the onset of hapten-induced contact hypersensitivity in BALB/c and C57BL/6 mice

1. To study the role of interleukin (IL)-4 in the onset of contact hypersensitivity (CH) in mice, the effect of IL-4 gene-depletion and anti-IL-4 monoclonal antibody treatment on dinitrofluorobenzene (DNFB)-induced CH was examined. Simultaneously, to clarify the effect of background gene, DNFB-induced CH in BALB/c and C57BL/6 mice was compared. 2. Five repeated topical applications of DNFB to the ears of mice resulted in CH of the ears in terms of increases in ear thickness and histopathological changes. The magnitude of ear thickness increase in BALB/c mice was almost three times greater than that in C57BL/6 mice. 3. The CH in BALB/c mice was significantly suppressed by IL-4 gene-depletion and anti-IL-4 monoclonal antibody treatment. In contrast, the symptoms of dermatitis in C57BL/6 mice were slightly affected by the same treatment. These changes corresponded well to the production of specific IgE antibody. 4. Total IgE antibody production and the expression of productive Cepsilon mRNA were dramatically suppressed by IL-4 gene-depletion and anti-IL-4 treatment in BALB/c and C57BL/6 mice. Neither total IgG nor IgM levels in either strain of mice was altered by depletion of IL-4. 5. The expression of IFN-gamma in the skin lesion was dramatically suppressed by IL-4 gene-depletion in BALB/c mice, but not in C57BL/6 mice. 6. These findings indicate that IL-4 plays an important role in the onset of DNFB-induced CH in BALB/c mice, but not in C57BL/6 mice.

Spatiotemporal changes of fibronectin, tenascin-C, fibulin-1, and fibulin-2 in the skin during the development of chronic contact dermatitis

In order to elucidate how chronic inflammation affects the organization of the extracellular matrix in the skin, a prolonged allergic contact dermatitis was induced in a mouse by repeated application to the ear of 2,4-dinitrofluorobenzene every 3 d for 66 d. Subsequently, the spatiotemporal changes of fibronectin, tenascin-C, fibulin-1, and fibulin-2 in the skin were examined. In the acute phase of inflammation (day 3-day 12), the amount of fibronectin and tenascin-C increased markedly and were degraded, whereas the amount of fibulin-2 changed slightly. Abundant deposition of tenascin-C was observed in the connective tissue. Fibulin-1 and fibulin-2 distributed as fine fibrils. In contrast, the amounts of fibronectin and tenascin-C decreased and their degradation was suppressed in the chronic phase (day 15-day 66), but the amount of fibulin-2 increased. Tenascin-C was observed mainly at and underneath the epidermal basement membrane. In the subepidermal region, many fibulin-2-positive microfibrils were distributed. The amount and distribution of fibulin-1 did not change markedly in either phase. MMP-like enzymes of 62 kDa, probably activated MMP-2, were upregulated in the chronic phase, whereas components of 92, 85, or 67 kDa were highly induced in the acute phase. These results suggest that chronic inflammation in allergic contact dermatitis is associated with temporal changes in the expression, deposition, and degradation of inducible extracellular matrix components.

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

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

Local lymph node assay: differentiating allergic and irritant responses using flow cytometry

The murine local lymph node assay (LLNA) is a method for assessing the contact sensitization potential of chemicals. Based on events that occur during the induction phase of a contact sensitization response, the LLNA measures the in vivo proliferation of cells in the draining lymph nodes (DLNs) of mice following topical exposure to chemicals. In terms of predictive identification of important skin sensitizers, the LLNA has been shown to be at least as sensitive as, and much more reliable than, current guinea pig tests. However, proliferation has also been observed following treatment with some irritants. In an attempt to distinguish allergic from irritant-induced proliferation, flow cytometric techniques have been used to examine the phenotype of lymphocyte subsets in the DLNs as well as markers of T-lymphocyte activation and memory. Mice were treated on the ears for 3 consecutive days with allergens or irritants. The DLNs were harvested 72 h after the final treatment. Single-cell suspensions were prepared, counted, and stained for analysis of the percentages of T cells and B cells and T-cell expression of two adhesion molecules that have been associated with differentiating naïve and activated/memory T cells, CD62L (L-selectin) and CD44 (H-cam). Increases in lymph node cellularity were observed in both allergen- and irritant-treated mice relative to naïve and vehicle-treated animals. Mice treated with allergens showed a preferential increase in the percentage of B220(+) B cells compared with irritant-treated mice. Treatment with allergens, but not irritants, resulted in a selective increase in the percentages of CD4(+) and CD8(+) cells expressing the T-cell activation/memory phenotype CD62L(lo)CD44(hi). Taken together, flow cytometric analysis of cell phenotype and expression of T-cell activation/memory markers may provide important information for differentiating allergen- and irritant-induced proliferative responses in the DLNs of chemically treated mice.

Neutrophil chemokine production in the skin following scald injury

The present study was conducted to determine whether local production of neutrophil chemoattractant cytokines preceded the influx of neutrophils following dermal scald injury. To accomplish this, dermal tissue was examined for inflammatory infiltrate and the level of KC, a murine homolog of human interleukin-8, at various time points after scald injury. The studies reveal that there was a largely neutrophilic infiltrate at 1 day post-injury which persisted for 4 days. Dermal KC levels increased significantly at 4 h, returned to baseline at 8 h and were elevated again from 1 to 3 days post-burn (P < 0.01). At 3 days post-burn, KC was elevated 15-fold above the level in sham treated mice (P < 0.01). These observations demonstrate that the influx of neutrophils into the skin follows the expression of KC in the skin. This suggests that it should be possible to alter neutrophil accumulation at the wound site by manipulating the local chemokine signal.

Cytotoxicity is mandatory for CD8(+) T cell-mediated contact hypersensitivity

Contact hypersensitivity (CHS) is a T cell-mediated skin inflammation induced by epicutaneous exposure to haptens in sensitized individuals. We have previously reported that CHS to dinitrofluorobenzene in mice is mediated by major histocompatibility complex (MHC) class I-restricted CD8(+) T cells. In this study, we show that CD8(+) T cells mediate the skin inflammation through their cytotoxic activity. The contribution of specific cytotoxic T lymphocytes (CTLs) to the CHS reaction was examined both in vivo and in vitro, using mice deficient in perforin and/or Fas/Fas ligand (FasL) pathways involved in cytotoxicity. Mice double deficient in perforin and FasL were able to develop hapten-specific CD8(+) T cells in the lymphoid organs but did not show CHS reaction. However, they did not generate hapten-specific CTLs, demonstrating that the CHS reaction is dependent on cytotoxic activity. In contrast, Fas-deficient lpr mice, FasL-deficient gld mice, and perforin-deficient mice developed a normal CHS reaction and were able to generate hapten-specific CTLs, suggesting that CHS requires either the Fas/FasL or the perforin pathway. This was confirmed by in vitro studies showing that the hapten-specific CTL activity was exclusively mediated by MHC class I-restricted CD8(+) T cells which could use either the perforin or the Fas/FasL pathway for their lytic activity. Thus, cytotoxic CD8(+) T cells, commonly implicated in the host defence against tumors and viral infections, could also mediate harmful delayed-type hypersensitivity reactions.

Epicutaneous administration of hapten through patch application augments TH2 responses which can downregulate the elicitation of murine contact hypersensitivity

BACKGROUND AND OBJECTIVE

Allergic contact dermatitis and its animal model, contact hypersensitivity (CHS), have long been documented as type 1 T-cell-predominant immune responses. Although type 1/type 2 T-cell deviation has been repeatedly demonstrated to play an important role in many human diseases and their animal models, the potential of tilting type 1/type 2 T-cell differentiation of CHS by modulating the manner of administration and dosage of hapten remains unexplored. This study examined the effect of these two factors on type 1/type 2 balance of CHS.

METHODS

ELISA methods for detection of isotypes of hapten-specific antibodies and cytokine profiles of in vitro reactivation culture as well as ear-swelling assay were used to indicate type 1 or type 2 T-cell immune responses.

RESULTS

In this paper, it was demonstrated that dosage of hapten has no effect on the type 1/ type 2 T-cell balance of CHS, whereas epicutaneous administration of hapten through patch application could tilt the type 1/type 2 balance to decrease type 1 and to augment type 2 T-cell responses. Patch application-induced modulation is still effective in ever-sensitized mice and the augmented type 2 T-cell responses are persistent and increase progressively in strength after repeated immunizations. Moreover, it was demonstrated that the augmented type 2 T-cell response can downregulate the elicitation of CHS. The major mediating cells of the enhanced type 2 T-cell responses were determined to be CD4+ T cells (TH2 cells).

CONCLUSIONS

These data show that epicutaneous administration of hapten through patch application augments TH2 response which can downregulate the elicitation of murine CHS. This exploration may contribute to the understanding of regulatory mechanisms involved in contact allergy.

Mast cell activation and migration to lymph nodes during induction of an immune response in mice

The mast cell response in skin and lymph nodes was examined during the sensitization phase of dinitrofluorobenzene (DNFB)-induced contact hypersensitivity in mice. Degranulation of 62% of mast cells in DNFB-exposed skin was evident within 30 min of a dual application of DNFB, reaching a peak of 77% at 24 h, and persisting in 42% after 5 d. Abundant expression of macrophage inflammatory protein (MIP)-1alpha and MIP-1beta mRNAs and proteins was observed in keratinocytes, and mast cell degranulation was significantly inhibited after administration of neutralizing antibodies to MIP-1alpha, but not MIP-1beta. During DNFB sensitization, the mast cell density in the skin decreased by half, concurrent with a fivefold expansion of mast cell numbers in draining lymph nodes. Fluorescent-labeled mast cells injected into the skin appeared in draining lymph nodes after application of DNFB, followed by subsequent migration to the spleen. In lymph nodes, mast cells were an abundant and predominant source of MIP-1beta, neutralization of which partially inhibited T lymphocyte recruitment. These results indicate that mast cells contribute to the induction of this primary immune response by activation at and migration from the site of antigen encounter to draining lymph nodes, wherein they mediate T lymphocyte recruitment by production of MIP-1beta.

Human IP-10 selectively promotes dominance of polyclonally activated and environmental antigen-driven IFN-gamma over IL-4 responses

Human interferon-inducible protein 10 (IP-10) differs from most chemokines in its apparent specificity for activated T lymphocytes. We hypothesized that IP-10 was relevant not only for recruiting T cells to inflammatory sites, but also for regulating cytokine synthesis patterns. We examined the effect of recombinant human IP-10 (rhIP-10) on human interferon gamma (IFN-gamma) and interleukin 4 (IL-4) production by fresh peripheral blood mononuclear cells. We demonstrate for the first time that this CXC chemokine selectively up-regulates human T cell cytokine synthesis, with enhancement selectively targeted to promotion of Th1-like dominance. Superantigen (TSST-1), soluble anti-CD3 mAb, and phytohemagglutinin were used to activate distinct intracellular signaling pathways, thereby inducing quantitatively different IFN-gamma:IL-4 ratios. Selective enhancement of IFN-gamma responses was consistently observed, with median increases of 105-470%. Environmental antigens (Ag) were used to evaluate IP-10's effect on CD4-dependent, chloroquine-sensitive cytokine synthesis. Ag-driven IFN-gamma responses exhibited median 19- to 30-fold increases in the presence of nanomolar concentrations of rhIP-10. IL-4 responses were neither enhanced nor inhibited under any of the conditions tested. These findings suggest a potential role for this T cell-focused chemokine in maintenance of the default Th1-like responses usually seen to environmental Ag and indicate a potential application in the modulation of Ag-driven responses in vivo.

Required early complement activation in contact sensitivity with generation of local C5-dependent chemotactic activity, and late T cell interferon gamma: a possible initiating role of B cells

Complement (C) is an important component of innate immunity, and was also shown recently to participate in induction of acquired B cell humoral immunity. In this study, we present evidence that C also participates in acquired T cell immunity. We found that C was involved in early events of the efferent elicitation phase of contact sensitivity (CS), and delayed-type hypersensitivity (DTH). Thus, CS and DTH were inhibited by administration of a C-blocker, soluble recombinant C receptor-1 (sCR1), when given 30 min before, but not 3 h after local antigen challenge. Among C components, local C5 were thought crucial to elicitation of CS, since local administration of anti-C5 monoclonal antibodies or locally injected C-depleting cobra venom factor also inhibited CS and DTH. These findings were consistent with our previous finding of the importance of C5 for CS elicitation, using congenitally C5-deficient mice. To dissect the mechanism of C dependence in CS, we demonstrated that locally increased early macrophage chemotactic activity (probably C5a) in evolving CS skin extracts, as well as late elaboration of IFN-gamma, were both inhibited by anti-C treatment. In addition, histological analysis showed that leukocyte recruitment into CS ear sites was similarly C-dependent. Furthermore, an initiating role of B cell-derived C-fixing immunoglobulin was suggested by demonstration of impaired CS responses in B cell-deficient mice. In summary, these results suggest that C was activated locally, perhaps via a B cell product, in an important early component of the stepwise events necessary to elicit CS, leading to local production of C5-dependent macrophage chemotactic activity and later IFN-gamma, and subsequently leading to cell infiltration, for development of T cell-dependent CS.

Selective modulation of T cell memory markers CD62L and CD44 on murine draining lymph node cells following allergen and irritant treatment

Naive and activated T cells are known to express different adhesion molecules and are thought to exhibit different migratory patterns that result from their expression of discrete adhesion molecules. Two adhesion molecules that have been associated with differentiating naive and activated/memory T cells are CD62L (L-selectin) and CD44 (H-CAM). It has been demonstrated previously that naive T cells express a CD62LhiCD44lo phenotype, whereas memory T cells exhibit a CD62LloCD44hi phenotype. The purpose of the present investigation was to determine whether chemical allergens, in contrast to irritants, would induce a CD62LloCD44hi phenotype on CD4 and/or CD8 T cells isolated from draining lymph nodes (DLN) of treated mice. Mice were treated on the ears for 3 consecutive days with concentrations of allergens or irritants which caused an increase in the number of DLN cells. The DLN were excised 72 hr following the final chemical treatment and cells prepared for analysis by flow cytometry. In mice treated with the allergen trinitrochlorobenzene an increase in the percentage of CD4+ cells expressing CD62LloCD44(hi) was observed compared to cells isolated from mice treated with the irritant benzalkonium chloride or vehicle treated mice. Mice treated with dintrochlorobenzene had an increase in the percentage of CD4+ cells expressing CD62LloCD44(hi) that was dose dependent and peaked at 72 hr following the final allergen treatment. Concomitant with changes on CD4+ cells, increases in the percentage of CD8+ cells expressing CD62LloCD44hi were observed with allergens, but not with irritants. Increases in the percentage of CD4+ and CD8+ cells expressing CD62LloCD44(hi) were observed with other allergens including oxazolone and alpha-hexylcinnamaldehyde, but not the irritant sodium lauryl sulfate. These data demonstrate that allergens, but not irritants, cause a selective and reproducible increase in the percentage of CD4+ and CD8+ cells expressing the T cell activation/memory phenotype CD62LloCD44hi. Analysis of T cell activation/memory markers may be useful in differentiating allergen and irritant responses in the draining lymph nodes of chemically treated mice.