[Show abstract][Hide abstract] ABSTRACT: Regulatory T cells (Tregs) are a specialized subpopulation of T cells that control the immune response and thereby maintain immune system homeostasis and tolerance to self-antigens. Many subsets of CD4(+) Tregs have been identified, including Foxp3(+), Tr1, Th3, and Foxp3neg iT(R)35 cells. In this study, we identified a new subset of CD4(+)VEGFR1(high) Tregs that have immunosuppressive capacity. CD4(+)VEGFR1high T cells, which constitute approximately 1.0% of CD4(+) T cells, are hyporesponsive to T-cell antigen receptor stimulation. Surface marker and FoxP3 expression analysis revealed that CD4(+)VEGFR1(high) T cells are distinct from known Tregs. CD4(+)VEGFR1(high) T cells suppressed the proliferation of CD4(+)CD25(-) T cell as efficiently as CD4(+)CD25(high) natural Tregs in a contact-independent manner. Furthermore, adoptive transfer of CD4(+)VEGFR1(+) T cells from wild type to RAG-2-deficient C57BL/6 mice inhibited effector T-cell-mediated inflammatory bowel disease. Thus, we report CD4(+) VEGFR1(high) T cells as a novel subset of Tregs that regulate the inflammatory response in the intestinal tract.Cellular & Molecular Immunology advance online publication, 27 July 2015; doi:10.1038/cmi.2015.71.
[Show abstract][Hide abstract] ABSTRACT: Maximum engraftment of transplanted islets is essential for the clinical application of a subcutaneous site. Significant barriers to the current approaches are associated with their low effectiveness, complexity and unproven biosafety. Here, we evaluated and optimized a fibrin-islet composite for effective glycemic control in a subcutaneous site whose environment is highly hypoxic due to low vascularization potential. In the setting of xenogeneic porcine islet transplantation into the subcutaneous space of a diabetic mouse, the in vivo islet functions were greatly affected by the concentrations of fibrinogen and thrombin. The optimized hydrogel-type fibrin remarkably reduced the marginal islet mass to approximately one tenth that of islets without fibrin. This marginal islet mass was comparable to that in the setting of the subcapsular space of the kidney, which is a highly vascularized organ. Highly vascularized structures were generated inside and on the outer surface of the grafts. A hydrogel-type fibrin-islet composite established early diabetic control within an average of 3.4days after the transplantation. In the mechanistic studies, fibrin promoted local angiogenesis, enhanced islet viability and prevented fragmentation of islets into single cells. In conclusion, in situ application of hydrogel-type fibrin-islet composite may be a promising modality in the clinical success of subcutaneous islet transplantation.
[Show abstract][Hide abstract] ABSTRACT: Mesenchymal stem cells (MSCs) are multipotent, non-hematopoietic stem cells that exhibit the capacity to inhibit the proliferation of a variety of immune cells. However, the underlying mechanisms of the immunosuppressive effects of MSCs are still obscure. Therefore, we attempted to identify the mechanisms underlying immunosuppression toward the activated T lymphocytes by MSCs in a murine model. In particular, we aimed to find possible factors derived from MSCs that drive this phenomenon. We found that T lymphocytes incubated with conditioned media of MSCs (MSC CM) entered into apoptosis and were subjected to cell cycle arrest during the course of activation, and these phenomena were accompanied by the reduction of IL-2 production. Specifically, matrix metalloproteinases (MMPs) derived from MSCs caused cleavage of IL-2 receptor α (CD25) from the surface of activated T cells, and as a consequence, IL-2 signaling in response to engagement of the IL-2 receptor (IL-2R) was downregulated. The inhibition of MMP activity in the MSC CM by GM6001 abrogated CD25 cleavage and restored IL-2 production from the activated splenocytes. However, the blockade of MMP activity could not fully restore the proliferative response and apoptosis of T cells altered by MSC CM. In conclusion, MSC-derived MMPs have a significant role in the suppression of IL-2 production through induction of CD25 cleavage and have a partial role in the suppression of T cell proliferation.
[Show abstract][Hide abstract] ABSTRACT: Memory T cells specific for donor antigens are currently recognized as a significant barrier for maintaining a successful transplant. Furthermore, it has been shown that commonly used immunosuppressive drugs do not alleviate this memory response. Here, we report that rapamycin allows significant proliferation of memory T cells and bortezomib can abrogate the proliferation of rapamycin-resistant memory T cells when preserving the survival of regulatory T cells.
Peripheral blood mononuclear cells freshly isolated from non-human primates were stimulated with anti-CD3/CD28 antibodies, and inhibitory and apoptotic effects of rapamycin and bortezomib on memory T-cell proliferation were investigated. The CD95 marker in CD3+ T cells was used for the separate enrichment of memory T cells and naïve T cells.
Rapamycin at the level even higher than therapeutic concentration could not suppress the proliferation of a significant proportion of memory T cells. However, the combined administration of bortezomib and rapamycin abrogated the proliferation of rapamycin-resistant memory T cells. Furthermore, bortezomib preserved the survival of preexisting CD4+ FoxP3+ regulatory T cells, while inducing apoptosis of CD4+ FoxP3- conventional T cells. The combined administration of low doses of rapamycin and bortezomib also exerted an additive effect on suppressing T-cell proliferation. Cytokine analysis demonstrated that bortezomib could not only suppress rapamycin-permissive interleukin (IL)-6 production, but also production of interferon (IFN)-gamma, IL-4, and IL-10.
This article provides in vitro data from which immunosuppressive regimens for the effective control of memory T cells in non-human preclinical experiments and in clinical trials are selected.
[Show abstract][Hide abstract] ABSTRACT: Human neural stem cells (hNSCs) can control inflammation in the central nervous system, although the underlying mechanisms are not understood fully. We investigated the immunomodulatory effect of hNSCs on human T cells and the underlying mechanisms. Culture supernatant from an immortalized hNSC cell line, HB1.F3, which has a therapeutic effect on acute stroke and intracerebral hemorrhage, suppressed the proliferation of allogeneically or mitogenically stimulated human peripheral T cells, including the CD3(+)CD103(+) subpopulation. CFSE labeling and flow cytometry showed that the suppression of proliferation was caused by cell cycle arrest and induction of apoptosis. The lack of significant change in caspase-8 levels and the significant reduction in Bcl-2 expression in the affected T cells suggest that the intrinsic pathway plays a major role in soluble-factor-mediated T-cell apoptosis. The addition of culture supernatant from hNSCs to activated T cells reduced the expression of the activation markers CD69 and CD25 at 24 hr after activation, but at 48 hr only CD69 was down-regulated. A cytometry bead assay showed that the secretion of interleukin (IL)-2 decreased significantly, whereas that of IL-4, IL-10, tumor necrosis factor-alpha, and interferon-gamma increased. These results show that hNSCs can negatively affect human peripheral T cells by suppressing their activation and proliferation through soluble mediators, suggesting that hNSCs have a bystander immunomodulatory effect on T cells.
Journal of Neuroscience Research 08/2009; 87(10):2264-72. DOI:10.1002/jnr.22050 · 2.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mesenchymal stem cells (MSCs) can inhibit T cell proliferation; however, the underlying mechanisms are not clear. In this study, we investigated the mechanisms of the immunoregulatory activity of MSCs on T cells. Irradiated MSCs co-cultured with either naïve or pre-activated T cells in a mixed lymphocyte reaction (MLR) significantly suppressed T cell proliferation in a dose-dependent manner, irrespective of allogeneic disparity between responders and MSCs. Transwell assays revealed that the suppressive effect was primarily mediated by soluble factors that induced apoptosis. Splenocytes stimulated with alloantigen in the presence of the MSC culture supernatant (CS) produced a significant amount of IL-10, which was attributed to an increase in the number of IL-10 secreting cells, confirmed by an ELISPOT assay. The blockade of IL-10 and IL-10 receptor interaction by anti-IL-10 or anti-IL-10-receptor antibodies abrogated the suppressive capacity of MSC CS, indicating that IL-10 plays a major role in the suppression of T cell proliferation. The addition of 1-methyl-DL-tryptophan (1-MT), an indoleamine 2,3-dioxygenase (IDO) inhibitor, also restored the proliferative capacity of T cells. In conclusion, we demonstrated that soluble mediators from culture supernatant of MSCs could suppress the proliferation of both naïve and pre-activated T cells in which IL-10 and IDO play important roles.
Experimental and Molecular Medicine 04/2009; 41(5). DOI:10.3858/emm.2009.41.5.035 · 3.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vascular endothelial growth factor (VEGF) is a proangiogenic mediator that promotes tumor growth. The role of VEGF in T lymphocytes is unknown. We found that T lymphocytes activated by either anti-CD3 monoclonal antibody (mAb) plus anti-CD28 mAb or by antigens on antigen-presenting cells transcribed mRNA for VEGF receptor 1 (VEGFR1) and VEGFR2. However, only VEGFR1 was expressed on the T cell surface. The addition of VEGF to either resting or activated T cells did not affect their proliferation, but VEGF increased IL-10 production and slightly decreased IFN-gamma production. A chemotaxis assay revealed that activated T lymphocytes migrate in response to VEGF. Our data suggest that VEGF has a direct immunomodulatory effect on T cells. Engagement of a high concentration of VEGF with VEGFR1 on T cells may cause T cells to migrate to tumor sites, and this interaction may play a role in IL-10-mediated immune evasion by tumor cells.
[Show abstract][Hide abstract] ABSTRACT: Protection of pancreatic islet beta cells from pro-inflammatory cytokines-induced cell death and functional impairment is a key issue in developing therapeutic interventions of type 1 diabetes mellitus including islet transplantation. The effects of IL-6 on the protection of beta cells in vitro and in vivo were examined. Freshly isolated islets or MIN6 beta cells, when pre-incubated with IL-6, showed significantly higher viabilities measured by MTT assay and FACS analysis of PI stained cells against pro-apoptotic signaling delivered by IL-1beta, TNF-alpha and IFN-gamma. Insulin secretory function was also significantly protected in static culture with glucose and KCl stimulation. In vivo assessment using marginal mass syngeneic islet transplantation in mouse model revealed IL-6 conferred significantly better blood glucose control and graft survival rate over 50 days. Conclusively, IL-6 protects pancreatic islets or beta-cells from inflammatory cytokines-induced cell death and functional impairment both in vitro and in vivo. This strategy could be exploited in the clinical setting to maintain functional islet mass.