Generation Of Regulatory CD4 Research Articles

Induction of Regulatory CD4+ Cells and Prolongation of Survival of Fully Allogeneic Murine Cardiac Grafts by Danazol

Danazol, a modified testosterone, has been used to treat endometriosis and pretreatment before in vitro fertilization and embryo transfer, although its reproductive mechanisms remain unclear. We investigated the effect of danazol on alloimmune responses in murine heart transplantation. CBA male mice (H2k) that underwent transplantation of C57BL/6 (B6, H2b) hearts received danazol (0.4 and 4 mg/kg/d) by intraperitoneal injection from the day of transplantation to days 6. We performed an adoptive transfer study to determine regulatory cells as well as cell proliferation, cytokine, and flow cytometry assessments. Danazol-treated (4 mg/kg/d) CBA mice showed prolonged allograft survival (median survival time [MST], 63 days). Moreover, secondary CBA recipients of whole splenocytes and CD4+ cells from primary danazol-treated (4 mg/kg/d) CBA recipients at 30 days after transplantation displayed prolonged allograft survival (MSTs, 29 and 60 days, respectively). Cell proliferation, interleukin (IL)-2, and interferon-γ were suppressed in danazol-treated mice, whereas IL-4 and IL-10 were up-regulated. Moreover, danazol directly suppressed alloproliferation in mixed leukocyte cultures. Flow cytometry studies showed an increased CD4+CD25+Foxp3+ cell population among splenocytes from danazol-treated mice. In conclusion, danazol induced prolonged cardiac allograft survival and generation of regulatory CD4+ cells.

Inhibition of Effector Function but Not T Cell Activation and Increase in FoxP3 Expression in T Cells Differentiated in the Presence of PP14

BackgroundT-helper polarization of naïve T cells is determined by a complex mechanism that involves many factors, eventually leading to activation of Th1, Th2, or Th17 responses or alternatively the generation of regulatory T cells. Placental Protein 14 (PP14) is a 28 kDa glycoprotein highly secreted in early pregnancy that is able to desensitize T cell receptor (TCR) signaling and modulate T cell activation.Methodology/Principal FindingsProlonged antigen-specific stimulation of T cells in the presence of PP14 resulted in an impaired secretion of IFN-γ, IL-5 and IL-17 upon restimulation, although the cells proliferated and expressed activation markers. Furthermore, the generation of regulatory CD4+CD25highFoxp3+ T cells was induced in the presence of PP14, in both antigen-specific as well as polyclonal stimulation. In accordance with previous reports, we found that the induction of FoxP3 expression by PP14 is accompanied by down regulation of the PI3K-mTOR signaling pathway.Conclusions/SignificanceThese data suggest that PP14 arrests T cells in a unique activated state that is not accompanied with the acquisition of effector function, together with promoting the generation of regulatory T cells. Taken together, our results may elucidate the role of PP14 in supporting immune tolerance in pregnancy by reducing T cell effector functions along with augmenting Treg differentiation.

IFN-γ Promotes Generation of IL-10 Secreting CD4+ T Cells that Suppress Generation of CD8 Responses in an Antigen-Experienced Host

Ags characterizing tumors or chronic viral infection are generally presented to the host immune system before specific immunotherapy is initiated, and consequent generation of regulatory CD4(+) T cells can inhibit induction of desired effector CD8 T cell responses. IL-10 produced in response to ongoing Ag exposure inhibits generation of CD8 T cells in an Ag-experienced host. We now show that this IL-10 is produced by Ag experienced CD4(+) glucocorticoid-induced tumor necrosis factor receptor(+) T cells that also secrete IFN-gamma upon antigenic stimulation, that IL-10 secretion by these cells is enhanced through IFN-gamma signaling, and, unexpectedly, that IFN-gamma signaling is required for inhibition of generation of Ag-specific CD8 T cell responses in an Ag-experienced host. Systemic inhibition of both IL-10 and IFN-gamma at the time of immunization may therefore facilitate induction of effective immunotherapeutic responses against tumor specific and viral Ags.

Involvement of the Liver in the Induction of CD8 T Cell Tolerance towards Oral Antigen

The liver is an organ with unique immune regulatory potential. This review highlights the experimental evidence for the involvement of hepatic cell populations in the induction of oral tolerance. Although immune tolerance towards oral antigens is mainly induced in the gastrointestinal tract within gut associated lymphatic tissue via generation of regulatory CD4 T cells, there is a further need for tolerance induction outside the gastrointestinal tract, because oral antigens rapidly distribute within minutes systemically through the blood stream. Besides hepatic dendritic cells, liver sinusoidal endothelial cells are active in the uptake and cross-presentation of oral antigens from portal venous blood and engage in the induction of CD8 T cell tolerance towards these antigens. These reports strengthen the notion that the liver participates in the induction of oral tolerance.

CD40 and Dendritic Cell Function

CD40 has emerged as a key signaling pathway for the function of B cells, monocytes, and dendritic cells (DC) in the immune system, and plays a major role in inflammatory pathways of nonhemopoietic cells. CD40 is expressed by monocytes and DC and is up-regulated when DC migrate from the periphery to draining lymph nodes (DLN) in response to microbial challenge. CD154 signaling by MHC-restricted, activated CD4+ T cells induces differentiation of DC, as defined by an increased surface expression of MHC, costimulatory, and adhesion molecules. Thus, CD40 functions in the adaptive immune response as a trigger for the expression of costimulatory molecules for efficient T-cell activation. CD40 ligation of DC also has the capacity to induce high levels of the cytokine IL-12, which polarizes CD4+ T cells toward a T helper 1 (Th1) type, enhances proliferation of CD8+ T cells, and activates NK cells. CD40 may also play an important role in the decision between tolerance and immunity and the generation of regulatory CD4+ T cells that are thought to maintain peripheral self-tolerance in vivo.