Role of interleukin-4 in down-regulation of contact sensitivity by gammadelta T cells from tolerized T-cell receptor alpha-/- mice

Obesity aggravates contact hypersensitivity reaction in mice

BACKGROUND

Obesity is associated with chronic, low-grade inflammation in tissues and predisposes to various complications, including inflammatory skin diseases. However, the link between obesity and contact hypersensitivity (CHS) is not fully understood.

OBJECTIVES

We sought to determine the influence of obesity on T helper 1 (Th1)-mediated CHS.

METHODS

The activity/phenotype/cytokine profile of the immune cells was tested in vivo and in vitro. Using quantitative polymerase chain reaction (qPCR) and fecal microbiota transplantation (FMT), we tested the role of a high-fat diet (HFD)-induced gut microbiota (GM) dysbiosis in increasing the effects of CHS.

RESULTS

Exacerbated CHS correlates with an increased inflammation-inducing GM in obese mice. We showed a proinflammatory milieu in the subcutaneous adipose tissue of obese mice, accompanied by proinflammatory CD4+ T cells and dendritic cells in skin draining lymph nodes and spleen. Obese interleukin (IL)-17A-/-B6 mice are protected from CHS aggravation, suggesting the importance of IL-17A in CHS aggravation in obesity.

CONCLUSIONS

Obesity creates a milieu that induces more potent CHS-effector cells but does not have effects on already activated CHS-effector cells. IL-17A is essential for the pathogenesis of enhanced CHS during obesity. Our study provides novel knowledge about antigen-specific responses in obesity, which may help with the improvement of existing treatment and/or in designing novel treatment for obesity-associated skin disorders.

Inhibitory effect of antidepressant drugs on contact hypersensitivity reaction is connected with their suppressive effect on NKT and CD8(+) T cells but not on TCR delta T cells

BACKGROUND

Contact hypersensitivity (CHS) reaction induced by a topical application of hapten is a cell-mediated antigen-specific type of skin inflammation mediated by interaction of several subtypes of T cell subpopulations. Recently, it has been shown that antidepressant drugs inhibit CHS reaction, although the mechanism of this effect remains unknown. The aim of the present study was to investigate the effect of 2-week desipramine or fluoxetine administration on the CHS reaction induced by picryl chloride (PCL) application in B10.PL mice and in knock-out mice established on B10.PL background: TCRδ(-/-) mice lacking TCRγδ T lymphocytes; β2m(-/-) mice lacking CD8(+) T lymphocytes and CD1d(-/-) mice lacking CD1d dependent natural killer T (NKT) lymphocytes.

METHODS

B10.PL, TCRδ(-/-), β2m(-/-) and CD1d(-/-) mice were divided into six groups: 1) vehicle-treated negative control group; 2) desipramine-treated negative control group; 3) fluoxetine-treated negative control group; 4) vehicle and PCL-treated group (positive control group); 5) desipramine and PCL-treated group; and 6) fluoxetine and PCL-treated group. CHS to PCL was tested by evaluation of ear swelling. Metabolic activity of spleen and lymph node cells were estimated by MTT test.

RESULTS

The antidepressants significantly suppressed the CHS reaction in B10.PL mice: desipramine by 55% and fluoxetine by 42% compared to the positive control. This effect was even stronger in TCRδ(-/-) mice, in which fluoxetine reduced the ear swelling by 73% in comparison with the vehicle-treated positive control group. On the other hand, desipramine and fluoxetine did not inhibit CHS reaction in β2m(-/-) and CD1d(-/-) mice. Moreover, PCL increased metabolic and/or proliferative activity of splenocytes in all four strains of mice whereas the antidepressants decreased this activity of splenocytes in B10.PL, TCRδ(-/-) and CD1d(-/-) mice.

CONCLUSION

The results of the present study show that lack of CD8(+) T cells or NKT cells abolishes the immunosuppressive effect of antidepressant drugs on PCL-induced CHS reaction in mice. These results suggest that antidepressant drug-induced inhibition of CHS reaction is connected with their inhibitory effect on ability of CD8(+) T cells and NKT cells to induce and/or escalate CHS reaction. TCRγδ cells seem not to be involved in antidepressant-induced suppression of CHS.

Direct crosstalk between mast cell-TNF and TNFR1-expressing endothelia mediates local tissue inflammation

Signaling through tumor necrosis factor receptor 1 (TNFR1) controls bacterial infections and the induction of inflammatory Th1 cell-mediated autoimmune diseases. By dissecting Th1 cell-mediated delayed-type hypersensitivity responses (DTHRs) into single steps, we localized a central defect to the missing TNFR1 expression by endothelial cells (ECs). Adoptive transfer and mast cell knockin experiments into Kit(W)/Kit(W-v), TNF(-/-), and TNFR1(-/-) mice showed that the signaling defect exclusively affects mast cell-EC interactions but not T cells or antigen-presenting cells. As a consequence, TNFR1(-/-) mice had strongly reduced mRNA and protein expression of P-selectin, E-selectin, ICAM-1, and VCAM-1 during DTHR elicitation. In consequence, intravital fluorescence microscopy revealed up to 80% reduction of leukocyte rolling and firm adhesion in TNFR1(-/-) mice. As substitution of TNF(-/-) mice with TNF-producing mast cells fully restored DTHR in these mice, signaling of mast cell-derived TNF through TNFR1-expressing ECs is essential for the recruitment of leukocytes into sites of inflammation.

Epithelial Defence by γδ T Cells

Gamma delta T cells constitute a separate lineage of T lymphocytes which differ from conventional alpha beta T cells with regard to T cell receptor (TCR) repertoire and tissue localization. In murine skin, gamma delta T cells expressing a canonical V gamma5 TCR are abundant and contribute as so-called dendritic epidermal T cells to local immune surveillance. In humans, major subsets of gammadelta T cells are recognized on the basis of their TCR V delta usage. While V delta2 cells dominate in the peripheral blood, V delta1 cells are preferentially localized in mucosal tissue including the intestinal epithelia. In this article we summarize basic features of intraepithelial gamma delta T cells and discuss their possible role in epithelial defence.

Potentiation of immunological tolerance induction in adult mice by co-administration of pooled normal IgG and oral tolerogens: a potential therapeutic approach for autoimmune diseases

Oral tolerance can be defined as the inability of an adult animal to produce specific antibodies or cellular immune responses upon conventional immunization, after oral antigenic administration. Recently, the oral administration of antigens has gained renewed interest because of the possibility of inducing tolerance in nonimmunized adult animals and, consequently, opening up the theoretical possibility of preventing or treating diseases caused by malfunction of the immune system. This strategy has been proven to be useful in the prevention of allergic and autoimmune diseases in rodents, as well as in the amelioration of certain autoimmune diseases in humans. Although there is experimental and clinical evidence for the usefulness of oral tolerance in medical practice, the mechanisms responsible for this phenomenon are still poorly understood, and the results obtained are not always satisfactory. Herein, we show that the thymus is required for the induction and maintenance of oral tolerance, providing evidence that it is not a pure form of clonal deletion-based peripheral tolerance. Oral tolerance could therefore depend on the formation and release to the periphery of regulatory T cells, such as gammadelta or alphabeta T cells, by the thymus. This finding may have profound implications for the treatment of autoimmune diseases, since most of them are associated with thymic hypofunction. On the other hand, due to so far unknown mechanisms, the intraperitoneal co-administration of normal IgG to mice orally treated with tolerogen leads to a sustained and intense immunological tolerance, both in euthymic and thymectomized mice, including those of the lupus erythematosus-prone NZB x NZW lineage. This approach for inducing and maintaining tolerance in thymus-deficient conditions is discussed and put forth herein as a new evidence-based proposition for the therapy of autoimmune diseases.

Restoration of human immunodeficiency virus-1-specific responses in patients changing from protease to non-nucleoside reverse transcriptase inhibitor-based antiretroviral therapy

The effect of altering antiretroviral therapy (ART) on responses to viral, recall and human immunodeficiency virus (HIV)-1-specific recombinant antigens and interleukin-2 (IL-2) in HIV-1-infected patients was assessed. A longitudinal cohort study in eight HIV-1 infected individuals following a clinically indicated therapy change (seven for drug intolerance and one for virological failure) from protease inhibitor (PI) to non-nucleoside reverse transcriptase inhibitor (NNRTI)-based antiretroviral regimens was performed. CD4 T-cell counts, viral loads, lymphoproliferative responses, cytokine production and latent proviral deoxyribonucleic acid (DNA) were measured at baseline and at weeks 12 and 24 after therapy substitution. Following therapy-switch there was a 33% proportional increase in mitogen response (95% confidence interval (CI), 3-33%) and a 31% increase (95% CI, 15-48%) in viral and recall-antigen responses. Six patients developed proliferative responses to low concentration IL-2 stimulation. All patients demonstrated an increase in median HIV-1-specific responses, as three had detectable virus at baseline (two being viral rebound); this may reflect an autovaccination effect. Proviral DNA changes largely reflected plasma HIV-1 ribonucleic acid (RNA). In conclusion, NNRTI substitution for a PI may favour immune reconstitution with an improvement in HIV-1-specific responses, which may reflect differential effects on antigen processing and presentation, an autovaccination effect or alternatively a potential suppressive effect of the PI.

Th2 cytokines, IgE and mast cells play a crucial role in the induction of para-phenylenediamine-induced contact hypersensitivity in mice

We previously reported the establishment of a mouse model system of contact hypersensitivity (CHS) to paraphenylemediamine (PPD). In order to analyse the functional contribution of Th2 cytokines, IL-4 and IL-5, in PPD induced CHS, STAT6 deficient (STAT6-/-) and wild-type control (WT) mice (C57BL/6) were immunized by the topical application of a PPD solution, and then the subsequent skin reactions were examined. Ear swelling was significantly reduced with a delayed peak response in STAT6-/- mice as compared with that of WT mice. A histological analysis showed the infiltration of both eosinophils and neutrophils in the skin of STAT6-/- mice challenged 24 h previously to significantly decrease in comparison with that in the WT mice. The expression of Th2 cytokines (IL-4, IL-5) by ELISA in the PPD-challenged skin tissue specimens as well as the IgE and IgG1 response after challenge were also profoundly reduced in the STAT6-/- mice. The adoptive transfer of the serum obtained from sensitized WT mice for the putative IgE transfer induced a peak response at 3 h and 24 h after challenge. To further investigate the role of mast cells in the induction of PPD-CHS, mast cell deficient W/Wv mice were sensitized with PPD and then were challenged. Maximal ear swelling was detected from 12 to 24 h and another small peak response was observed at 1 h in+/+mice, whereas only a small peak response at 24 h was detected in W/Wv mice. These data indicate that not only Th2 cytokines and IgE but also mast cells play an essential role in the induction of PPD-CHS.

IL-12 reverses established tolerance mediated by TCRalphabeta+ but not by TCRgammadelta+ suppressor T cells

Topical cutaneous painting with chemically reactive haptens induces the ability to subsequently elicit contact sensitivity (CS) responses in the skin. These CS responses are in vivo examples of acquired, antigen (Ag)-specific T cell immunity, and are a form of delayed-type hypersensitivity (DTH). In contrast, high dose i.v. administration of the hapten can induce Ag-specific tolerance. In some instances this specific immune hyporeactivity is due to suppressor T cells. We investigated the effect of IL-12 on reversal of tolerance due to suppressor T cells that were induced by i.v. administration of hapten in either normal TCRalpha+/+, or in immunodeficient TCRalpha-/- mice. In the TCRalpha+/+ mice, tolerance is mediated by TCRalphabeta+ suppressor T cells, while in the TCRalpha-/- mice the tolerance is due to suppressive TCRgammadelta+ cells. Treatment with IL-12 reversed suppressor mediated by the TCRalphabeta+ cells, but did not affect tolerance due to TCRgammadelta+ suppressor cells. Another difference was that the alphabetaTCR+ suppressor cells produced a soluble suppressor factor that could replace the surppressor cells, while gammadeltaTCR+ suppressor cells did not. We hypothesized that IL-12 may strengthen responses of target CS-effector T cells influenced by the hapten-MHC-specificity of alphabeta suppresssor cells, or suppressor factor. On the other hand, gammadeltaTCR+ suppressive cells likely have specificity for the hapten alone, and are not MHC-restricted, and therefore probably do not operate via peptide-MHC interactions, that could be strengthened by IL-12. The ability of IL-12 to strengthen the resistance of CS-effector T cells to alphabeta TCR suppressor cells, may be due to the ability of IL-12 to increase T cell costimulation mediated by signaling mechanisms acting via B7.1 and B7.2. In contrast, gammadeltaTCR+ suppressor cells, that are largely hapten-specific, probably do not interact with peptide/MHC complexes on APC, and thus are not affected by IL-12 strengthening of co-stimulation.