Development and function of innate polyclonal TCRalphabeta+ CD8+ thymocytes.

Innate CD8 T cells are found in mutant mouse models, but whether they are produced in a normal thymus remains controversial. Using the RAG2p-GFP mouse model, we found that ∼10% of TCRαß(+) CD4(-)CD8(+) thymocytes were innate polyclonal T cells (GFP(+)CD44(hi)). Relative to conventional T cells, innate CD8 thymocytes displayed increased cell surface amounts of B7-H1, CD2, CD5, CD38, IL-2Rß, and IL-4Rα and downmodulation of TCRß. Moreover, they overexpressed several transcripts, including T-bet, Id3, Klf2, and, most of all, Eomes. Innate CD8 thymocytes were positively selected, mainly by nonhematopoietic MHCIa(+) cells. They rapidly produced high levels of IFN-γ upon stimulation and readily proliferated in response to IL-2 and IL-4. Furthermore, low numbers of innate CD8 thymocytes were sufficient to help conventional CD8 T cells expand and secrete cytokine following Ag recognition. This helper effect depended on CD44-mediated interactions between innate and conventional CD8 T cells. We concluded that innate TCRαß(+) CD8 T cells represent a sizeable proportion of normal thymocytes whose development and function differ in many ways from those of conventional CD8 T cells.

Adoptive transfer of mesenchymal stromal cells accelerates intestinal epithelium recovery of irradiated mice in an interleukin-6-dependent manner.

BACKGROUND AIMS: Apoptosis of radiosensitive cells in the bone marrow and gut is a serious, at times life-threatening, complication arising from radiation exposure. METHODS: We investigated whether adoptive transfer of allogeneic bone marrow-derived mesenchymal stromal cells (MSC) could exert cytoprotective and life-sparing effects in a mouse model of sublethal total body irradiation (TBI). RESULTS: We demonstrated that a single intraperitoneal injection of C57Bl/6 MSC given to major histocompatibility complex (MHC)-mismatched Balb/c mice within 24 h of sublethal TBI significantly reduced mortality in a dose-dependent manner. Histologic analysis and Ki67 immunostaining of jejunum sections collected 3 and 6 days post-TBI indicated that MSC protected the gastrointestinal epithelium from TBI-induced damage and significantly accelerated recovery of the gut by stimulating proliferation of the crypt cell pool. Using interleukin-6(-/-) (IL-6) MSC, we demonstrated that IL-6 expressed by MSC played a role in gastrointestinal epithelium regeneration. CONCLUSIONS: Our results suggest that allogeneic MHC-mismatched MSC may be exploited to reduce gastrointestinal complications and mortality arising from ionizing radiation exposure.

A dendritic cell population generated by a fusion of GM-CSF and IL-21 induces tumor-antigen-specific immunity.

We have previously shown that the fusion of GM-CSF and IL-21 (GIFT-21) possesses a potent immune stimulatory effect on myeloid cells. In this study, we define the effect of GIFT-21 on naive murine monocytes (GIFT-21 dendritic cells [DCs]), which express increased levels of Gr-1, CD45R, MHC class I, CD80, CD86, and CXCR4 and suppress CD11c and MHC class II. Compared with conventional dendritic cells, GIFT-21 DCs produced substantially more CCL2, IL-6, TNF-α, and IFN-α and induced significantly greater production of IFN-γ by CD8(+) T cells in MHC class I-restricted Ag presentation assays. B16 melanoma and D2F2 Neu breast cancer growth was inhibited in mice treated with Ag-naive GIFT-21 DCs. This effect was lost in CD8(-/-) and CCR2(-/-) mice and when mice were treated with ß(2)-microglobulin-deficient GIFT-21 DCs, indicating that GIFT-21 DCs migrated to and sampled from the tumors to present tumor Ags to CCL2 recruited CD8(+) T cells via MHC class I. We propose that autologous GIFT-21 DCs may serve as a cell therapy platform for the treatment of cancer.

Induction of cardiac angiogenesis requires killer cell lectin-like receptor 1 and α4ß7 integrin expression by NK cells.

Recent findings indicate that NK cells are involved in cardiac repair following myocardial infarction. The aim of this study is to investigate the role NK cells in infarct angiogenesis and cardiac remodeling. In normal C57BL/6 mice, myelomonocytic inflammatory cells invaded infarcted heart within 24 h followed by a lymphoid/NK cell infiltrate by day 6, accompanied by substantial expression of IL-2, TNF-α, and CCL2. In contrast, NOD SCID mice had virtually no lymphoid cells infiltrating the heart and did not upregulate IL-2 levels. In vitro and in vivo, IL-2-activated NK cells promoted TNF-α-stimulated endothelial cell proliferation, enhanced angiogenesis and reduced fibrosis within the infarcted myocardium. Adoptive transfer of IL-2-activated NK cells to NOD SCID mice improved post-myocardial infarction angiogenesis. RNA silencing technology and neutralizing Abs demonstrated that this process involved α4ß7 integrin/VCAM-1 and killer cell lectin-like receptor 1/N-cadherin-specific binding. In this study, we show that IL-2-activated NK cells reduce myocardial collagen deposition along with an increase in neovascularization following acute cardiac ischemia through specific interaction with endothelial cells. These data define a potential role of activated NK cells in cardiac angiogenesis and open new perspectives for the treatment of ischemic diseases.

Mesenchymal stromal cells engineered to express erythropoietin induce anti-erythropoietin antibodies and anemia in allorecipients.

Autologous bone marrow mesenchymal stromal cells (MSCs) have been successfully used for the delivery of erythropoietin (EPO) in murine models of anemia and myocardial infarction. For clinical applications where a transient effect would be adequate, such as myocardial infarction, the use of EPO-engineered universal donor allogeneic MSCs would be a substantial convenience. We thus investigated whether MSCs from C57BL/6 mice would permit robust transient EPO delivery in normal BALB/c allorecipients. Implantation of MSCs overexpressing murine EPO led to increases in hematocrit in syngeneic and allogeneic mice, but the latter eventually developed severe anemia due to acquired neutralizing anti-EPO antibodies. As MSCs constitutively produce the CCL2 chemokine which may behave as an adjuvant to the anti-EPO immune response, experiments were performed using EPO-engineered MSCs derived from CCL2(-/-) mice and similar results were obtained. In conclusion, MHC-mismatched MSCs can break the tolerance to autoantigens and lead to the development of pathogenic autoantibodies.

Hierarchical scaffold design for mesenchymal stem cell-based gene therapy of hemophilia B.

Gene therapy for hemophilia B and other hereditary plasma protein deficiencies showed great promise in pre-clinical and early clinical trials. However, safety concerns about in vivo delivery of viral vectors and poor post-transplant survival of ex vivo modified cells remain key hurdles for clinical translation of gene therapy. We here describe a 3D scaffold system based on porous hydroxyapatite-PLGA composites coated with biomineralized collagen 1. When combined with autologous gene-engineered factor IX (hFIX) positive mesenchymal stem cells (MSCs) and implanted in hemophilic mice, these scaffolds supported long-term engraftment and systemic protein delivery by MSCs in vivo. Optimization of the scaffolds at the macro-, micro- and nanoscales provided efficient cell delivery capacity, MSC self-renewal and osteogenesis respectively, concurrent with sustained delivery of hFIX. In conclusion, the use of gene-enhanced MSC-seeded scaffolds may be of practical use for treatment of hemophilia B and other plasma protein deficiencies.