Cross-talk between gammadelta T lymphocytes and immune cells in humoral response

Gene expression pattern of TCR repertoire and alteration expression of IL-17A gene of γδ T cells in patients with acute myocardial infarction

BACKGROUND

γδ T cells are associated with the pathogenesis of coronary atherosclerotic heart disease, but the relationship between the development of acute myocardial infarction (AMI) and γδ T cells is not clear. So we attempt to investigate the expression pattern and clonality of T cell receptor (TCR) repertoire of γδ T cells in AMI patients, analyze the expression levels of regulatory genes Foxp3 and IL-17A, and characterize the correlation between γδ T cells and the pathogenesis of AMI.

METHODS

25 patients diagnosed with ST-segment-elevation AMI were enrolled and 14 healthy individuals were recruited as the controls. RT-PCR and GeneScan were used to analyze the complementarity-determining region 3 sizes of TCR γδ repertoire genes in sorted γδ T cells from peripheral blood mononuclear cells (PBMCs). RQ-PCR was used to detect the gene expression levels of Foxp3, IL-17A and TCR Vγ subfamilies in sorted γδ T cells. All the patients were followed up for recordings of clinical endpoints.

RESULTS

The mRNA gene expression levels of TCR Vγ1, Vγ2, and Vγ3 subfamilies in AMI patients were significantly higher than those in healthy controls. The expression pattern was Vγ1 > Vγ2 > Vγ3 in AMI patients, while Vγ1 > Vγ3 > Vγ2 in healthy controls. The significantly restricted expression of TCR Vδ subfamilies were also found in AMI patients. The expression frequencies of TCR Vδ7 and TCR Vδ6 in AMI patients were significantly lower than those in healthy controls. The high clonal expansion frequencies of the TCR Vδ8, Vδ4 and Vδ3 were determined in AMI patients. High expression of Foxp3 gene was found in AMI PBMCs, while high expression of IL-17A was found in AMI γδ+ cells.

CONCLUSIONS

Restrictive expression of TCR γδ repertoire and alteration expression of IL-17A gene are the important characteristics of γδ T cells in AMI patients, which might be related to the immune response and clinical outcome. γδ T cells might play a key role in the pathological progress of AMI and associated with the IL-17A mediated pathway.

Gene expression pattern of Treg and TCR Vγ subfamily T cells before and after specific immunotherapy in allergic rhinitis

BACKGROUND

T regulatory cell (Treg) plays a critical role in respiratory allergy and allergen-specific immunotherapy (SIT), and γδ T cells might participate in mediating Treg quantity and/or function in some immunological diseases. To further characterize whether γδ T cells could influence Treg in allergic rhinitis (AR) and SIT, we investigated the expression pattern of Treg's Foxp3 gene and γδ T cell receptor (TCR) Vγ subfamily genes in peripheral blood mononuclear cells (PBMCs) of AR patients before and after SIT.

METHODS

Eighteen AR patients undergoing effective SIT with house dust mite extract for one year were recruited. Visual Analogue Scale (VAS) was applied to evaluate the severity. Immunofluorescence quantification analysis was performed to determine the serum specific IgE (sIgE) content. Real-time PCR was used to detect the expression levels of Foxp3 and TCR Vγ subfamilies. Ten healthy volunteers were recruited as the controls.

RESULTS

Nasal uni-VAS score after SIT was significantly lower than that before SIT, while serum sIgE content was similar before and after SIT. Expression levels of Foxp3 and TCR Vγ subfamilies in AR patients before treatment were significantly lower than those in healthy subjects. Expression levels of VγI and II were similar before and after SIT, while expression levels of Foxp3 and VγIII after SIT were significantly higher than those before. Before SIT, the significant positive correlation was observed between expression levels of Foxp3 and VγI, II, III, while negative correlation was observed between Foxp3, VγIII and VAS. After SIT, the significant positive correlation between expression levels of Foxp3 and VγIII and negative correlation between Foxp3, VγIII and VAS were observed.

CONCLUSIONS

Treg and Vγ subfamily T cells were in a dynamic equilibrium in AR patients before and after effective immunotherapy for one year. The early improvement of symptoms following immunotherapy might be independent of the serum sIgE content in AR patients, but associated with the reconstitution of T cell immunity.

Epicutaneous immunization with DNP-BSA induces CD4+ CD25+ Treg cells that inhibit Tc1-mediated CS

As we have shown previously that protein antigen applied epicutaneously (EC) in mice inhibits TNP-specific Th1-mediated contact sensitivity (CS), we postulated that the maneuver of EC immunization might also suppress Tc1-dependent CS response. Here we showed that EC immunization of normal mice with 2,4-dinitrophenylated bovine serum albumin (DNP-BSA) applied on the skin in the form of a patch induces a state of subsequent unresponsiveness due to regulatory T cells (Treg) that inhibited sensitization and elicitation of effector T-cell responses. Suppression is transferable in vivo by TCRαβ(+) CD4(+) CD25(+) lymphocytes harvested from lymph nodes (LNs) of skin-patched animals. Flow cytometry revealed that EC immunization with DNP-BSA increased TCRαβ(+) CD4(+) CD25(+) FoxP3(+) lymphocytes in subcutaneous LNs, suggesting that observed suppression was mediated by Treg cells. Further, in vitro experiments showed that EC immunization with DNP-BSA prior to 1-fluoro-2,4-dinitrobenzen sensitization suppressed LN cell proliferation and inhibited production of TNF-α, IL-12 and IFN-γ. Using a transwell system or anti-CTLA-4 mAb, we found that EC induced suppression required direct Treg-effector cell contact and is CTLA-4-dependent.

Functions of skin-resident γδ T cells

The murine epidermis contains resident T cells that express a canonical γδ TCR and arise from fetal thymic precursors. These cells are termed dendritic epidermal T cells (DETC) and use a TCR that is restricted to the skin in adult animals. DETC produce low levels of cytokines and growth factors that contribute to epidermal homeostasis. Upon activation, DETC can secrete large amounts of inflammatory molecules which participate in the communication between DETC, neighboring keratinocytes and langerhans cells. Chemokines produced by DETC may recruit inflammatory cells to the epidermis. In addition, cell-cell mediated immune responses also appear important for epidermal-T cell communication. Information is provided which supports a crucial role for DETC in inflammation, wound healing, and tumor surveillance.

GammadeltaT cells regulate the development of hapten-specific CD8+ effector T cells in contact hypersensitivity responses

It has been reported that gammadeltaT cells are required for transfer of contact hypersensitivity responses by hapten-primed T cells. The mechanism by which they do so, however, remains to be elucidated. To specifically investigate the role of gammadeltaT cells in the development of contact hypersensitivity, this study employed Tdelta gene knockout mice that are deficient in gammadeltaT cells but are normal in the development of alphabetaT cells. The result indicates that contact hypersensitivity responses were significantly greater in gammadeltaT cell deficient mice than in wild-type mice. Similar results were obtained when wild-type mice were depleted of gammadeltaT cells with antibody treatment before hapten sensitization. Depletion of CD4+ T cells did not affect the increased contact hypersensitivity response in gammadeltaT cell deficient mice, suggesting that the effect of gammadeltaT cells is on CD8+ T cells and does not require CD4+ T cells. Further experiments demonstrated that primed CD8+ T cells from the deficient mice exhibited significantly higher CTL activity. The cytokine profile of CD4+ T cells was not significantly altered. Transfer of primed lymph node cells from hapten-primed gammadeltaT cell deficient mice elicited a similar level of contact hypersensitivity in naive wild-type and the deficient recipient mice, indicating that gammadeltaT cells have little effect on the elicitation of primed T cells and contact hypersensitivity responses. We conclude that gammadeltaT cells downregulate contact hypersensitivity responses to hapten sensitization by limiting the development of hapten-specific CD8+ effector T cells during sensitization and that this effect is independent of CD4+ T cells.

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.