Role of CD4+ and CD8+ T cells in the rejection of concordant pancreas xenografts

A preclinical evaluation of alternative site for islet allotransplantation

The bone marrow cavity (BMC) has recently been identified as an alternative site to the liver for islet transplantation. This study aimed to compare the BMC with the liver as an islet allotransplantation site in diabetic monkeys. Diabetes was induced in Rhesus monkeys using streptozocin, and the monkeys were then divided into the following three groups: Group1 (islets transplanted in the liver with immunosuppressant), Group 2 (islets transplanted in the tibial BMC), and Group 3 (islets transplanted in the tibial BMC with immunosuppressant). The C-peptide and blood glucose levels were preoperatively measured. An intravenous glucose tolerance test (IVGTT) was conducted to assess graft function, and complete blood cell counts were performed to assess cell population changes. Cytokine expression was measured using an enzyme-linked immune sorbent assay (ELISA) and MILLIPLEX. Five monkeys in Group 3 exhibited a significantly increased insulin-independent time compared with the other groups (Group 1: 78.2 ± 19.0 days; Group 2: 58.8 ± 17.0 days; Group 3: 189.6 ± 26.2 days) and demonstrated increases in plasma C-peptide 4 months after transplantation. The infusion procedure was not associated with adverse effects. Functional islets in the BMC were observed 225 days after transplantation using the dithizone (DTZ) and insulin/glucagon stains. Our results showed that allogeneic islets transplanted in the BMC of diabetic Rhesus monkeys remained alive and functional for a longer time than those transplanted in the liver. This study was the first successful demonstration of allogeneic islet engraftment in the BMC of non-human primates (NHPs).

Common and small molecules as the ultimate regulatory and effector mediators of antigen-specific transplantation reactions

In spite of intensive research, the molecular basis of allograft and xenograft rejection still remains not fully understood. The acute rejection of an allograft is associated with the intragraft Th1 cytokine response, while tolerance of an allograft or xenograft rejection is accompanied by a higher production of the Th2 cytokines interleukin (IL)-4 and IL-10. Nevertheless, these cytokines are not the final regulatory and effector molecules mediating transplantation reactions. Data indicate that the functioning of common molecules with enzymatic activities, such are inducible nitric oxide synthase (iNOS), arginase, heme oxygenase-1 (HO-1) or indoleamine-2,3-dioxygenase (IDO), the bioavailability of their substrates (L-arginine, tryptophan, heme) and the cytotoxic and regulatory actions of their small gaseous products (NO, CO) can be the ultimate mechanisms responsible for effector or regulatory reactions. Using models of transplantation immunity and tolerance we show that T cell receptor-mediated recognition of allogeneic or xenogeneic antigens as well as the balance between immunity/tolerance induces distinct cytokine production profiles. The ratio between Th1 and Th2 cytokines efficiently regulates the expression of genes for common enzymes, such as iNOS, arginase, HO-1 and IDO. These enzymes may compete for substrates, such as L-arginine or tryptophan, and the final product of their activity are small molecules (NO, CO) displaying effector or regulatory functions of the immune system. Thus, it is suggested that in spite of the high immunological specificity of transplatation reaction, the ultimate players in regulatory and effector functions could be small and common molecules.

Role of OGR1 in myeloid-derived cells in prostate cancer

Ovarian cancer G-protein-coupled-receptor-1 (OGR1) is a tumor metastasis suppressor in prostate cancer (PCa). OGR1 knockout mice (ogr1(-/-)) are grossly normal under physiological conditions, however, reduced melanoma tumorigenesis has been observed, with the mechanisms of this reduction completely unknown. In this work, we demonstrated that OGR1 deficiency in host cells significantly reduced tumorigenesis of PCa in mice. Adoptive transfer of WT CD11b(+) Gr1(+) double positive (DP) cells, but not T cells, was sufficient to allow tumor development in ogr1(-/-) mice. The expression of an M1 macrophage marker, inducible nitric oxide synthase (iNOS) was higher and expression of an M2 macrophage marker, arginase-1 (Arg 1) was lower in tumors from ogr1(-/-) mice compared with WT mice. Furthermore, coinjection of transgenic adenocarcinoma mouse prostate (TRAMP)-C2 cells with WT, but not ogr1(-/-) macrophages, increased tumor incidence in ogr1(-/-) mice. T-cell depletion experiments suggested that T cells were required for tumor rejection in ogr1(-/-)mice, although OGR1 expression in T cells may not be necessary. In summary, the expression of OGR1 in myeloid-derived cells, especially in DP cells, was required for PCa tumor cell-induced immunosuppression.

Allogeneic Adipose-Derived Stem Cells with Low Immunogenicity Constructing Tissue-Engineered Bone for Repairing Bone Defects in Pigs

The ideal cells for tissue engineering should have the following characteristics: easy obtainment, safety, immune privilege, the capability of self-renewal, and multipotency. Adipose-derived stem cells (ADSCs) are a promising candidate. However, the immunogenicity of allogeneic mesenchymal stem cells limits their long-term benefits. In this study, we introduced human cytomegalovirus US2/US3 gene into the ADSCs to decrease the expression of MHC I protein of ADSCs and reduce the activation of T-cells of the recipient animals. Moreover, the biosafety and biological characteristics of ADSCs transfected with the US2/US3 genes (ADSCs-US2/US3) were similar to normal ADSCs. Then we took ADSCs-US2/US3 to construct a tissue-engineered bone for repairing bone defects in pigs and found that there were no great differences in repair effects or healing time between the allogeneic ADSCs-US2/US3 group and the autologous ADSC group. These results suggest that allogeneic ADSCs-US2/US3 have the advantages of biological safety, low immunogenicity, and effective osteogenesis. Such barely immunogenic ADSCs will be crucial for the success of future tissue-regenerative approaches.

Effector mechanisms of the autoimmune syndrome in the murine model of autoimmune polyglandular syndrome type 1

Mutations in the Aire gene result in a clinical phenomenon known as Autoimmune Polyglandular Syndrome (APS) Type I, which classically manifests as a triad of adrenal insufficiency, hypoparathyroidism, and chronic mucocutaneous infections. In addition to this triad, a number of other autoimmune diseases have been observed in APS1 patients including Sjögren's syndrome, vitiligo, alopecia, uveitis, and others. Aire-deficient mice, the animal model for APS1, have highlighted the role of the thymus in the disease process and demonstrated a failure in central tolerance in aire-deficient mice. However, autoantibodies have been observed against multiple organs in both mice and humans, making it unclear what the specific role of B and T cells are in the pathogenesis of disease. Using the aire-deficient mouse as a preclinical model for APS1, we have investigated the relative contribution of specific lymphocyte populations, with the goal of identifying the cell populations which may be targeted for rational therapeutic design. In this study, we show that T cells are indispensable to the breakdown of self-tolerance, in contrast to B cells which play a more limited role in autoimmunity. Th1 polarized CD4(+) T cells, in particular, are major contributors to the autoimmune response. With this knowledge, we go on to use therapies targeted at T cells to investigate their ability to modulate disease in vivo. Depletion of CD4(+) T cells using a neutralizing Ab ameliorated the disease process. Thus, therapies targeted specifically at the CD4(+) T cell subset may help control autoimmune disease in patients with APS1.

CD4+ T cells are sufficient to elicit allograft rejection and major histocompatibility complex class I molecule is required to induce recurrent autoimmune diabetes after pancreas transplantation in mice

BACKGROUND

We characterized the role of T cell subsets and major histocompatibility complex molecules in allograft rejection and recurrence of autoimmune diabetes.

METHODS

Adoptive cell transfer and vascularized segmental pancreas transplantation were performed in mice.

RESULTS

In an alloimmune response model, transfer of nondiabetic CD4, but not CD8 T cells, elicited pancreas allograft rejection in streptozotocin (STZ)-induced diabetic NOD/scid mice. Pancreas allografts were acutely rejected in STZ-induced diabetic NOD/beta2m mice (confirmed the absence of major histocompatibility complex [MHC] class I and CD8 T cells) and permanently accepted in NOD/CIIT mice (confirmed the absence of MHC class II and CD4 T cells). The results suggest that rejection of pancreas allograft is CD4-dependent and MHC class I-independent. In the autoimmune diabetes model, whole spleen cells obtained from diabetic NOD mice induced autoimmune diabetes in NOD/scid and NOD/CIIT mice, but the onset of diabetes was delayed in NOD/beta2m mice. However, the purified diabetic T cells failed to elicit autoimmune diabetes in NOD/beta2m mice. NOD/scid and NOD/CIIT pancreas grafts were acutely destroyed whereas four of six NOD/beta2m pancreas grafts were permanently accepted in autoimmune diabetic NOD mice.

CONCLUSION

CD4 T cells are sufficient for the induction of allograft rejection, and MHC class I molecule is required to induce recurrent autoimmune diabetes after pancreas transplantation in mice.

Spontaneous autoimmunity prevented by thymic expression of a single self-antigen

The expression of self-antigen in the thymus is believed to be responsible for the deletion of autoreactive T lymphocytes, a critical process in the maintenance of unresponsiveness to self. The Autoimmune regulator (Aire) gene, which is defective in the disorder autoimmune polyglandular syndrome type 1, has been shown to promote the thymic expression of self-antigens. A clear link, however, between specific thymic self-antigens and a single autoimmune phenotype in this model has been lacking. We show that autoimmune eye disease in aire-deficient mice develops as a result of loss of thymic expression of a single eye antigen, interphotoreceptor retinoid-binding protein (IRBP). In addition, lack of IRBP expression solely in the thymus, even in the presence of aire expression, is sufficient to trigger spontaneous eye-specific autoimmunity. These results suggest that failure of thymic expression of selective single self-antigens can be sufficient to cause organ-specific autoimmune disease, even in otherwise self-tolerant individuals.

Donor Lymphocyte Infusion Induces Long-Term Donor-Specific Cardiac Xenograft Survival through Activation of Recipient Double-Negative Regulatory T Cells

Previous studies have shown that pretransplant donor lymphocyte infusion (DLI) can enhance xenograft survival. However, the mechanism by which DLI induces xenograft survival remains obscure. Using T cell subset-deficient mice as recipients we show that CD4+, but not CD8+, T cells are necessary to mediate the rejection of concordant cardiac xenografts. Adoptive transfer of naive CD4+ T cells induces rejection of accepted cardiac xenografts in CD4-/- mice. This rejection can be prevented by pretransplant DLI in the absence of any other treatment. Furthermore, we demonstrate that DLI activates alphabeta-TCR+CD3+CD4-CD8- double-negative (DN) regulatory T (Treg) cells in xenograft recipients, and that DLI-activated DN Treg cells can inhibit the proliferation of donor-specific xenoreactive CD4+ T cells in vitro. More importantly, adoptive transfer of DLI-activated DN Treg cells from xenograft recipients can suppress the proliferation of xenoreactive CD4+ T cells and their ability to produce IL-2 and IFN-gamma in vivo. Adoptive transfer of DLI-activated DN Treg cells also prevents CD4+ T cell-mediated cardiac xenograft rejection in an Ag-specific fashion. These data provide direct evidence that DLI can activate recipient DN Treg cells, which can induce donor-specific long-term cardiac xenograft survival by suppressing the proliferation and function of donor-specific CD4+ T cells in vivo.

An animal model of autoimmune emphysema

Although cigarette smoking is implicated in the pathogenesis of emphysema, the precise mechanisms of chronic progressive alveolar septal destruction are not well understood. We show, in a novel animal model, that immunocompetent, but not athymic, nude rats injected intraperitoneally with xenogeneic endothelial cells (ECs) produce antibodies against ECs and develop emphysema. Immunization with ECs also leads to alveolar septal cell apoptosis and activation of matrix metalloproteases MMP-9 and MMP-2. Anti-EC antibodies cause EC apoptosis in vitro and emphysema in passively immunized mice. Moreover, immunization also causes accumulation of CD4+ T cells in the lung. Adoptive transfer of pathogenic, spleen-derived CD4+ cells into naive immunocompetent animal also results in emphysema. This study shows for the first time that humoral- and CD4+ cell-dependent mechanisms are sufficient to trigger the development of emphysema, suggesting that alveolar septal cell destruction might result from immune mechanisms.

Leukocyte adhesion molecules and reactive oxygen species in preeclampsia

OBJECTIVE

The aim of our study was to compare the expression of leukocyte adhesion molecules, intracellular reactive oxygen species, and vasoactive substances in preeclampsia and matched normotensive pregnancies and to explore differences between pregnancy and the nonpregnant state regarding these parameters.

METHODS

Flow cytometry was used to analyze the monocyte and granulocyte expression of adhesion molecules from 20 matched pairs of preeclampsia/normotensive pregnancies and 12 nonpregnant subjects. Basal levels of CD11b, CD11c, CD62L, and CD14 were measured. In addition, expression of human lymphocyte antigen-DR, CD4, CD8, and CD4/CD8 ratio were assessed. Basal reactive oxygen species levels, as well as reactivity upon in vitro stimulation with phorbol 12-myristate 13-acetate, were measured in monocytes and granulocytes with the probes dihydroethidium, dichlorofluorescein-diacetate, and dihydrorhodamine-123. Further, the plasma levels of endothelin-1, the nitric oxide metabolites nitrite/nitrate, and total antioxidant status were analyzed.

RESULTS

Monocytes expressed significantly higher levels of CD11b and CD14 in preeclamptic patients compared with normotensive pregnant subjects, whereas CD11c was elevated on both monocytes and granulocytes in pregnancy compared with the nonpregnant state. Both monocytes and granulocytes displayed higher basal, as well as phorbol 12-myristate 13-acetate-stimulated, amounts of reactive oxygen species in the preeclampsia group compared with the normotensive group. We also found the endothelin-1 and antioxidant levels significantly elevated in preeclampsia patients compared with normotensive subjects, whereas no differences were seen between the groups regarding nitrite/nitrate levels.

CONCLUSION

These results show that the maternal blood leukocytes are activated in preeclampsia and support the view that oxidative stress is a contributing factor in the pathophysiology of preeclampsia.