Conferring indirect allospecificity on CD4+CD25+ Tregs by TCR gene transfer favors transplantation tolerance in mice.

T cell responses to MHC-mismatched transplants can be mediated via direct recognition of allogeneic MHC molecules on the cells of the transplant or via recognition of allogeneic peptides presented on the surface of recipient APCs in recipient MHC molecules - a process known as indirect recognition. As CD4(+)CD25(+) Tregs play an important role in regulating alloresponses, we investigated whether mouse Tregs specific for allogeneic MHC molecules could be generated in vitro and could promote transplantation tolerance in immunocompetent recipient mice. Tregs able to directly recognize allogeneic MHC class II molecules (dTregs) were obtained by stimulating CD4(+)CD25(+) cells from C57BL/6 mice (H-2(b)) with allogeneic DCs from BALB/c mice (H-2(d)). To generate Tregs that indirectly recognized allogeneic MHC class II molecules, dTregs were retrovirally transduced with TCR genes conferring specificity for H-2K(d) presented by H-2A(b) MHC class II molecules. The dual direct and indirect allospecificity of the TCR-transduced Tregs was confirmed in vitro. In mice, TCR-transduced Tregs, but not dTregs, induced long-term survival of partially MHC-mismatched heart grafts when combined with short-term adjunctive immunosuppression. Further, although dTregs were only slightly less effective than TCR-transduced Tregs at inducing long-term survival of fully MHC-mismatched heart grafts, histologic analysis of long-surviving hearts demonstrated marked superiority of the TCR-transduced Tregs. Thus, Tregs specific for allogeneic MHC class II molecules are effective in promoting transplantation tolerance in mice, which suggests that such cells have clinical potential.

Is Danggui Safe to be Taken by Breast Cancer Patients?-A Skepticism Finally Answered by Comprehensive Preclinical Evidence.

Angelica sinensis (AS, Danggui) has long been regarded to stimulate breast cancer growth; hence, the use of AS in breast cancer patients remains a major concern for both patients and practitioners. Since safety studies of herbs would be unethical to carry out in patients, the present study aimed to investigate the potential unsafe effects of AS in a systematic pre-clinical approach. Human breast cancer cells, breast orthotopic tumor-bearing mouse models, as well as primary breast cancer cells from patients' tumors were used to evaluate the effect of AS hot water extract on the progression of breast tumors and/or growth of breast cancer cells. We showed that AS is not that stimulatory in breast cancer both in vitro and in vivo, though AS should still be used with caution in estrogen receptor-positive breast cancer patients. This novel approach of applying breast cancer cell lines, xenograft, and syngeneic tumors models, as well as primary breast cancer cells from patients' tumors in Chinese medicines safety evaluation was proven feasible. Our finding is important information for patients, Chinese medicine practitioners, and clinicians on the safety use of AS in breast cancer, which will affect future clinical practice.

Evaluation of the safety profiles of estrogenic Chinese herbal medicines in breast cancer.

BACKGROUND: An increasing number of breast cancer patients in Asian countries has been found to consume dietary supplements including phytoestrogen-rich Chinese herbal medicines with an expectation to alleviate the side effects of conventional cancer therapies. PURPOSE: The question of whether estrogenic Chinese herbal medicines are beneficial or detrimental to the health of breast cancer patients remains uncertain. STUDY DESIGN: The present study aimed at establishing a systematic approach to look at the safety profiles of estrogenic Chinese herbal medicines (CHM). METHODS: The effects of estrogenic CHM on the growth of human breast cancer cells as well as the progression of breast tumors in mice have been investigated. RESULTS: Our results demonstrated that among 10 selected estrogenic CHM, the aqueous extracts of Cistanche deserticola (CD) and Dioscorea opposita (DO) at 0.4 to 1.6 mg/ml significantly stimulated cell viability in both estrogen receptor (ER)-positive (MDA-MB-361 and MCF-7) and ER-negative (SKBR3 and MDA-MB-231) breast cancer cells. However, results from animal studies showed that no significant difference was found on the size of mouse 4T1 breast tumors in CD- and DO-treated mice when compared with the control group, while the number of proliferative cells were found to be increased in DO-treated group. Besides, CD and DO treatments induced significant immunomodulatory effects on 4T1 tumor-bearing mice by increasing the production of cytokines IL-2 and IFN-γ and modulation of regulatory T-cells. Furthermore, CD and DO treatments did not stimulate, but in fact suppressed human triple-negative MDA-MB-231 breast xenografts growth in immunodeficiency mice. CONCLUSION: The considerable concerns on the use of CD and DO in breast cancer patients could be relieved to some extents upon the findings of this pre-clinical study. The potential harmful effects of estrogenic Chinese herbal medicines on breast cancer growth should be verified in both cell-based and tumor-bearing mice models.

Altered proximal T cell receptor (TCR) signaling in human CD4+CD25+ regulatory T cells.

CD4+CD25+ regulatory T cells play an important role in peripheral tolerance. Upon T cell receptor (TCR)-mediated activation, the cells fail to proliferate but are induced to have a suppressor function. The intracellular signaling events that lead to their responses have not been elucidated. In this study, we have examined the proximal TCR signaling events in freshly isolated human CD4+CD25+ regulatory T cells after TCR ligation. In contrast to CD4+CD25- T cells, TCR ligation of CD4+CD25+ regulatory T cells by anti-CD3 cross-linking resulted in a lower calcium influx and extracellular signal-regulated kinase 1/2 phosphorylation. Examination of the CD3zeta chain phosphorylation status indicated that CD4+CD25+ regulatory T cells have poor phosphorylation of the protein and consequently, reduced recruitment of zeta-associated protein-70 to the TCR immunoreceptor tyrosine motif. The adaptor protein, Src homology 2 domain-containing leukocyte phosphoprotein of 76 kDa, which relays signals to downstream signaling components, also showed reduced phosphorylation, which correlated with reduced VAV guanine nucleotide exchange factors association. Consistent with other findings, the defect is accompanied with impaired actin cap formation, implicating a failure of actin remodeling of the cells. Together, our results demonstrate that CD4+CD25+ regulatory T cells have altered TCR proximal signaling pathways, which could be critical for inducing the distinct behavior of these cells.

Inhibition of TGF-ß signaling in combination with TLR7 ligation re-programs a tumoricidal phenotype in tumor-associated macrophages.

Inadequate immunity that occurs in a tumor environment is in part due to the presence of M2-type tumor-associated macrophages (TAMs). TGF-ß has a multi-functional role in tumor development including modulating the biological activity of both the tumor and TAMs. In this study, using an in vitro TAM/tumor cell co-culture system ligation of TLR7, which is expressed on TAMs but not the tumor cells, in the presence of TGF-ß receptor I inhibitor re-programmed the phenotype of the TAMs. In part they adopted the phenotype characteristic of M1-type macrophages, namely they had increased tumoricidal activity and elevated expression of iNOS, CD80 and MHC class II, while TGF-ß secretion was reduced. The reprogrammed phenotype was accompanied by enhanced NF-κB nuclear translocation. The pro-angiogenesis factor VEGF was down-regulated and in vivo the number of CD31-positive tumor capillaries was also reduced. Furthermore, in vivo we observed that TLR7 ligation/TGF-ß receptor I inhibition increased tumor apoptosis and elevated the number of CD4+, CD8+, and CD19+ cells as well as neutrophils infiltrating the tumor. Our data demonstrate that selective TLR stimulation with TGF-ß inhibition can reprogram TAMs towards an M1-like phenotype and thereby provides new perspectives in cancer therapy.

Novel immunomodulatory effects of adiponectin on dendritic cell functions.

Adiponectin (ADN) is an adipocytokine with anti-inflammatory properties. Although it has been reported that ADN can inhibit the immunostimulatory function of monocytes and macrophages, little is known of its effect on dendritic cells (DC). Recent data suggest that ADN can regulate immune responses. DCs are uniquely specialised antigen presenting cells that play a central role in the initiation of immunity and tolerance. In this study, we have investigated the immuno- modulatory effects of ADN on DC functions. We found that ADN has only moderate effect on the differentiation of murine bone marrow (BM) derived DCs but altered the phenotype of DCs. The expression of major histocompatibilty complex class II (MHCII), CD80 and CD86 on ADN conditioned DCs (ADN-DCs) was lower than that on untreated cells. The production of IL-12p40 was also suppressed in ADN-DCs. Interestingly, ADN treated DCs showed an increase in the expression of the inhibitory molecule, programmed death-1 ligand (PDL-1) compared to untreated cells. In vitro co-culture of ADN-DCs with allogeneic T cells led to a decrease in T cell proliferation and reduction of IL-2 production. Concomitant with that, a higher percentage of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) was detected in co-cultures of T cells and ADN-DCs. Blocking PD-1/PDL-1 pathway could partially restore T cell function. These findings suggest that the immunomodulatory effect of ADN on immune responses could be at least partially be mediated by its ability to alter DC function. The PD-1/PDL-1 pathway and the enhancement of Treg expansion are implicated in the immunomodulatory mechanisms.

PPAR-γ signaling and IL-5 inhibition together prevent chronic rejection of MHC Class II-mismatched cardiac grafts.

BACKGROUND: Chronic rejection can prevent long-term survival of organ transplants. Although the beneficial effects of peroxisome proliferator-activated receptor-gamma (PPAR-γ) in reducing graft rejection have been reported, the details of the underlying mechanisms remain unclear, especially in the context of modulating cellular infiltration and preventing vasculopathy and interstitial fibrosis. METHODS: The therapeutic effects of the PPAR-γ agonist, rosiglitazone, combined with anti-interleukin-5 are explored in a mouse model of MHC Class II-histoincompatible cardiac transplantation. RESULTS: Rosiglitazone treatment alone marginally increased long-term survival and reduced CD8 T-cell infiltration and vasculopathy in the grafts. However, there was no reduction in collagen deposition and interleukin (IL)-4, IL-5 and eosinophil infiltration were increased. Anti-IL-5 antibody treatment alone reduced eosinophil infiltration and collagen deposition, but had no effect on CD8 T-cell infiltration or vasculopathy. Combined treatment with anti-IL-5 antibody and rosiglitazone prevented graft rejection. Furthermore, rosiglitazone treatment increased adiponectin receptor II expression in grafts and on dendritic cells and T cells in vitro. Graft survival correlated with increased expression in grafts of the inhibitory molecule PD-L1. CONCLUSIONS: The findings obtained increase the knowledge on the mode of action of rosiglitazone in promoting the survival of MHC Class II-mismatched cardiac transplants in which the CD8 T cells and eosinophils play key roles. PPAR-γ signaling combined with IL-5 blockade prevents graft rejection.

Indefinite mouse heart allograft survival in recipient treated with CD4(+)CD25(+) regulatory T cells with indirect allospecificity and short term immunosuppression.

CD4(+)CD25(+) regulatory T cells (Tregs) play a crucial role in controlling immune responses. It is an appealing strategy to harness Tregs for adoptive cell therapy to induce tolerance to allografts. Several approaches have been developed to expand antigen-specific Tregs. Despite the large body of experimental data from murine studies demonstrating the great potential of these cells for clinical application, Treg adoptive transfer therapy was used in immunodeficient animals or in strain combinations with limited histiocompatibility. The aim of this study was to investigate whether Treg lines can protect from allograft rejection in a fully MHC-mismatched strain combination and whether the presence of Tregs with indirect allospecificity offered an advantage compared to self-reactive Tregs. Treg lines with self-specificity or with indirect allospecificity were generated by stimulating BL/6 CD4(+)CD25(+) T cells with autologous immature DCs either unpulsed or pulsed with K(d) peptide. The Treg lines were injected into recipient mice in combination with temporary depletion of CD8(+) T cells and a short course of Rapamycin. The data demonstrate that Treg lines with indirect allospecificity can be generated and most importantly they can induce indefinite survival of BALB/c hearts transplanted into BL/6 recipients when combined with short term immunosuppression. However, the Treg lines with self-specificity were only slightly less effective. The data presented in this study demonstrate the potential of ex vivo expanded Treg lines for adoptive cell therapy to promote transplantation tolerance.

Regulation of rat and human T-cell immune response by pharmacologically modified dendritic cells.

BACKGROUND: The central function of dendritic cells (DC) in inducing and preventing immune responses makes them ideal therapeutic targets for the induction of immunologic tolerance. In a rat in vivo model, we showed that dexamethasone-treated DC (Dex-DC) induced indirect pathway-mediated regulation and that CD4+CD25+ T cells were involved in the observed effects. The aim of the present study was to investigate the mechanisms underlying the acquired immunoregulatory properties of Dex-DC in the rat and human experimental systems. METHODS: After treatment with dexamethasone (Dex), the immunogenicity of Dex-DC was analyzed in T-cell proliferation and two-step hyporesponsiveness induction assays. After carboxyfluorescein diacetate succinimidyl ester labeling, CD4+CD25+ regulatory T-cell expansion was analyzed by flow cytometry, and cytokine secretion was measured by ELISA. RESULTS: In this study, we demonstrate in vitro that rat Dex-DC induced selective expansion of CD4+CD25+ regulatory T cells, which were responsible for alloantigen-specific hyporesponsiveness. The induction of regulatory T-cell division by rat Dex-DC was due to secretion of interleukin (IL)-2 by DC. Similarly, in human studies, monocyte-derived Dex-DC were also poorly immunogenic, were able to induce T-cell anergy in vitro, and expand a population of T cells with regulatory functions. This was accompanied by a change in the cytokine profile in DC and T cells in favor of IL-10. CONCLUSION: These data suggest that Dex-DC induced tolerance by different mechanisms in the two systems studied. Both rat and human Dex-DC were able to induce and expand regulatory T cells, which occurred in an IL-2 dependent manner in the rat system.