Donor-strain-derived immature dendritic cell pre-treatment induced hyporesponsiveness against allogeneic antigens

Cotransplantation of Mesenchymal Stem Cells and Immature Dendritic Cells Potentiates the Blood Glucose Control of Islet Allografts

BACKGROUND

Transplantation of islets is a promising alternative to treat type 1 diabetes (T1D), but graft rejection is the major obstacle to its application in clinical practice. We evaluated the effects of mesenchymal stem cells (MSCs) and immature dendritic cells (imDCs) on islet transplantation in diabetic model.

METHODS

The streptozotocin T1D model was established in BABL/c mice. Rat islets were isolated and identified with dithizone (DTZ) staining. MSCs and imDCs were isolated from bone marrow of syngenic mice. Islets, alone or along with MSCs and/or imDCs, were transplanted to the left kidney capsule of diabetic mice. The blood glucose levels and glycosylated hemoglobin levels after transplantation were monitored.

RESULTS

Cotransplantation significantly decreased blood glucose and glycosylated hemoglobin levels in the diabetes mice. Transplantation of 200 islets + 2 × 105 MSCs + 2 × 105 imDCs could not only restore normal blood glucose levels, but also significantly prolong graft survival for 12.6 ± 3.48 days.

CONCLUSIONS

Cotransplantation of allogenic islets with imDCs and/or MSCs can significantly promote graft survival, reverse hyperglycemia, and effectively control the glycosylated hemoglobin levels.

Combining Exosomes Derived from Immature DCs with Donor Antigen-Specific Treg Cells Induces Tolerance in a Rat Liver Allograft Model

Allograft tolerance is the ultimate goal in the field of transplantation immunology. Immature dendritic cells (imDCs) play an important role in establishing tolerance but have limitations, including potential for maturation, short lifespan in vivo and short storage times in vitro. However, exosomes (generally 30–100 nm) from imDCs (imDex) retain many source cell properties and may overcome these limitations. In previous reports, imDex prolonged the survival time of heart or intestine allografts. However, tolerance or long-term survival was not achieved unless immune suppressants were used. Regulatory T cells (Tregs) can protect allografts from immune rejection, and our previous study showed that the effects of imDex were significantly associated with Tregs. Therefore, we incorporated Tregs into the treatment protocol to further reduce or avoid suppressant use. We defined the optimal exosome dose as approximately 20 μg (per treatment before, during and after transplantation) in rat liver transplantation and the antigen-specific role of Tregs in protecting liver allografts. In the co-treatment group, recipients achieved long-term survival, and tolerance was induced. Moreover, imDex amplified Tregs, which required recipient DCs and were enhanced by IL-2. Fortunately, the expanded Tregs retained their regulatory ability and donor-specificity. Thus, imDex and donor-specific Tregs can collaboratively induce graft tolerance.

Value of phagocyte function screening for immunotoxicity of nanoparticles in vivo

Nanoparticles (NPs) present in the environment and in consumer products can cause immunotoxic effects. The immune system is very complex, and in vivo studies are the gold standard for evaluation. Due to the increased amount of NPs that are being developed, cellular screening assays to decrease the amount of NPs that have to be tested in vivo are highly needed. Effects on the unspecific immune system, such as effects on phagocytes, might be suitable for screening for immunotoxicity because these cells mediate unspecific and specific immune responses. They are present at epithelial barriers, in the blood, and in almost all organs. This review summarizes the effects of carbon, metal, and metal oxide NPs used in consumer and medical applications (gold, silver, titanium dioxide, silica dioxide, zinc oxide, and carbon nanotubes) and polystyrene NPs on the immune system. Effects in animal exposures through different routes are compared to the effects on isolated phagocytes. In addition, general problems in the testing of NPs, such as unknown exposure doses, as well as interference with assays are mentioned. NPs appear to induce a specific immunotoxic pattern consisting of the induction of inflammation in normal animals and aggravation of pathologies in disease models. The evaluation of particle action on several phagocyte functions in vitro may provide an indication on the potency of the particles to induce immunotoxicity in vivo. In combination with information on realistic exposure levels, in vitro studies on phagocytes may provide useful information on the health risks of NPs.

Involvement of Caveolin-1 in CD83 Internalization in Mouse Dendritic Cells

To become potent T-cell stimulators, DCs need to mature. Treatment with soluble CD83 (sCD83) induces immune tolerance and protects against transplant rejection by maintaining dendritic cells in an immature, tolerogenic state. Until now, the mechanism through which sCD83 keeps DCs immature has not been investigated. The internalizing pathway of CD83 was screened by Western blot, and the direct interactions between internalized proteins were verified through coimmunoprecipitation (co-IP) and transmission electron microscopy (TEM). CD83 plasma membrane levels were detected by Western blot using a plasma membrane protein extraction protocol. The changes in CD83 surface levels in DCs were detected by flow cytometry. Caveolin-1 function was detected in a kidney transplant model. In this study, we demonstrated that caveolin-1 could affect CD83 level during endocytosis in mouse DCs. Caveolin-1 coprecipitates with CD83, as demonstrated by co-IP analysis. TEM morphometric analysis of the entire CD83 distribution associated with internalized caveolin-1 demonstrated a significant interaction in cellular vesicles. sCD83 reduces endogenous CD83 plasma membrane levels, and caveolin-1 knockdown reverts CD83 levels in plasma membrane. sCD83 treatment decreases CD83 surface levels in DCs. siRNA to caveolin-1 in DCs inhibits this effect of sCD83. The effects of sCD83-treated DCs were proved in CD1 mice. Knocking down caveolin-1 in DCs obstructs the effects of sCD83 on kidney transplant. In conclusion, our data indicated that a caveolin-dependent endocytic pathway is involved in CD83 internalization in DCs and that caveolin-1 is involved in the activity of DCs.

Adoptive transfusion of tolerance dendritic cells prolongs the survival of skin allografts in mice: a systematic review

OBJECTIVE

We aim to systematically review adoptive transfusion of tolerogenic dendritic cells (Tol-DCs) induced by different ways to affect skin allograft survival in mice.

METHODS

We searched PubMed and EMbase for relevant studies and evaluated the quality of included ones. Taking skin allograft survival time as endpoint outcome, we displayed outcomes of each group using one forest map and dissected possible mechanisms underlying survival prolongation.

RESULTS

We included 21 studies, which reported four methods of inducing Tol-DCs with different extents of average allograft survival prolongation: skin allograft survival time was prolonged (the drug intervention group, 63.08 ± 42.92 days, 4.6 folds to control; the cytokine induction group: 26.17 ± 16.20 days, 1.8 folds; the gene modification group: 14.65 ± 17.89 days, 1.5 folds; other derivation group 9.63 ± 24.38 days, 0.5 fold). Possible mechanisms underlying survival prolongation included induction of donor-specific T cell hyporesponsiveness, reduction of cytotoxicity against allografts, Th0 skewing to Th2, and generation or expansion of Treg. Infusion of Tol-DCs in combination with immunosuppressive agents or costimulatory blockade contributed to longer prolongation. Compared to MiHA mismatch, MHCI/II mismatch was a much more important factor to cause skin allograft rejection.

CONCLUSION

For MHC or MiHA mismatched, allogeneic skin transplants inbred recipients, adoptive transfusion of Tol-DCs induced by 4 methods prolong skin allograft survival to different extents. Drug intervened Tol-DCs works best. Immunosuppressive agents and/or co-stimulatory blockade contribute to better outcomes. Yet more rigorous studies with larger sample size are needed and more attention to mechanisms should be paid.

Maturation-resistant dendritic cells ameliorate experimental autoimmune uveoretinitis

Background

Endogenous uveitis is a chronic inflammatory eye disease of human, which frequently leads to blindness. Experimental autoimmune uveoretinitis (EAU) is an animal disease model of human endogenous uveitis and can be induced in susceptible animals by immunization with retinal antigens. EAU resembles the key immunological characteristics of human disease in that both are CD4⁺ T-cell mediated diseases. Dendritic cells (DCs) are specialized antigen-presenting cells that are uniquely capable of activating naïve T cells. Regulation of immune responses through modulation of DCs has thus been tried extensively. Recently our group reported that donor strain-derived immature DC pretreatment successfully controlled the adverse immune response during allogeneic transplantation.

Methods

EAU was induced by immunization with human interphotoreceptor retinoid-binding protein (IRBP) peptide_1-20. Dendritic cells were differentiated from bone marrow in the presence of recombinant GM-CSF.

Results

In this study, we used paraformaldehyde-fixed bone marrow-derived DCs to maintain them in an immature state. Pretreatment with fixed immature DCs, but not fixed mature DCs, ameliorated the disease progression of EAU by inhibiting uveitogenic CD4⁺ T cell activation and differentiation.

Conclusion

Application of iBMDC prepared according to the protocol of this study would provide an important treatment modality for the autoimmune diseases and transplantation rejection.