How to cross immunogenetic hurdles to human embryonic stem cell transplantation

Implantation of human embryonic stem cells (hES), derived progenitors or mature cells derived from hES has great therapeutic potential for many diseases. If hES would come from genetically unrelated individuals, it would be probably rejected by the immune system of the recipient. Blood groups, MHC and minor antigens are the immunogenetic hurdles that have to be crossed for successful transplantation. Autologous transplantation with adult stem cells would be the best approach but several elements argue against this option. Classical immunosuppression, depleting antibody, induction of tolerance and stem cell banking are alternative methods that could be proposed to limit the risk of rejectio

The proinflammatory cytokines IL-2, IL-15 and IL-21 modulate the repertoire of mature human natural killer cell receptors

Natural killer (NK) cells play a crucial role in the immune response to micro-organisms and tumours. Recent evidence suggests that NK cells also regulate the adaptive T-cell response and that it might be possible to exploit this ability to eliminate autoreactive T cells in autoimmune disease and alloreactive T cells in transplantation. Mature NK cells consist of a highly diverse population of cells that expresses different receptors to facilitate recognition of diseased cells and possibly pathogens themselves. Ex vivo culture of NK cells with cytokines such as IL-2 and IL-15 is an approach that permits significant expansion of the NK cell subpopulations, which are likely to have potent antitumour, antiviral, or immunomodulatory effects in autoimmunity. Our data indicate that the addition of IL-21 has a synergistic effect by increasing the numbers of NK cells on a large scale. IL-2 and IL-15 may induce the expression of killer cell immunoglobulin-like receptors (KIRs) in KIR-negative populations, the c-lectin receptor NKG2D and the natural cytotoxic receptor NKp44. The addition of IL-21 to IL-15 or IL-2 can modify the pattern of the KIR receptors and inhibit NKp44 expression by reducing the expression of the adaptor DAP-12. IL-21 also preserved the production of interferon-γ and enhanced the cytotoxic properties of NK cells. Our findings indicate that the proinflammatory cytokines IL-2, IL-15 and IL-21 can modify the peripheral repertoire of NK cells. These properties may be used to endow subpopulations of NK cells with specific phenotypes, which may be used in ex vivo cellular immunotherapy strategies

Casimir dark energy, stabilization of the extra dimensions and Gauss–Bonnet term

A Casimir dark energy model in a five-dimensional and a six-dimensional spacetime including non-relativistic matter and a Gauss–Bonnet term is investigated. The Casimir energy can play the role of dark energy to drive the late-time acceleration of the universe while the radius of the extra dimensions can be stabilized. The qualitative analysis in four-dimensional spacetime shows that the contribution from the Gauss–Bonnet term will effectively slow down the radion field at the matter-dominated or radiation-dominated epochs so that it does not pass the point at which the minimum of the potential will arise before the minimum has formed. The field then is trapped at the minimum of the potential after the formation leading to the stabilization of the extra dimensions

The role of natural killer cells in the immune response against CMV infection in immunosuppressed patients

Natural Killer (NK) cells are part of the innate immune system and represent 5 to 15% of the total lymphocytes in a healthy individual. At their surface different families of inhibitory and activating receptors are expressed, where the killer immunoglobulin-like receptors (KIR) are of special interest. NK cells reactivity will depend on the binding of their receptors and their specific ligands, the major histocompatibility complex I (MHC-I). This KIR-MHC-I interaction plays an important role in transplantation. As transplanted patients are immunosuppressed, they represent an easy target to opportunistic infections, such as cytomegalovirus (CMV). Specific T-cells can clear CMV infection, but immunosuppressive drugs, which help to tolerate the graft, inhibit the activity of these T-cells. Interestingly, NK cells seem not affected by these drugs. The aim of this thesis is to investigate the anti-viral role of the NK cells during CMV infection after solid organ transplantation

Interaction of ES cell derived neural progenitor cells with natural killer cells and cytotoxic T cells

Knowing that human embryonic stem cells (HESC) can be derived into several different cells types render these cells very attractive to cure diseases. Unless these stem cells are originated from the patient itself, they will be isolated from a donor, who is genetically unrelated to the recipient. This situation will mimic an allogenic transplantation with an immune response against the transplanted cells. The immunogenicity of the HESC and the potential of NK and T-cells to target HESC and the lineage derived from HESC have to be addressed. Several different tests do exist to analyse NK cells and T-cells activity against HESC and its progenitor cells. In this chapter review the capacity of NK and T cells against neural progenitor derived from HESC, through a classical and a novel approach that combined the phenotype and also the functionality of the effector cells. In addition, we also demonstrate in the same test that we can determine the lysis of the progenitor cells by flow cytometry

Potential and Limitation of HLA-Based Banking of Human Pluripotent Stem Cells for Cell Therapy

Great hopes have been placed on human pluripotent stem (hPS) cells for therapy. Tissues or organs derived from hPS cells could be the best solution to cure many different human diseases, especially those who do not respond to standard medication or drugs, such as neurodegenerative diseases, heart failure, or diabetes. The origin of hPS is critical and the idea of creating a bank of well-characterized hPS cells has emerged, like the one that already exists for cord blood. However, the main obstacle in transplantation is the rejection of tissues or organ by the receiver, due to the three main immunological barriers: the human leukocyte antigen (HLA), the ABO blood group, and minor antigens. The problem could be circumvented by using autologous stem cells, like induced pluripotent stem (iPS) cells, derived directly from the patient. But iPS cells have limitations, especially regarding the disease of the recipient and possible difficulties to handle or prepare autologous iPS cells. Finally, reaching standards of good clinical or manufacturing practices could be challenging. That is why well-characterized and universal hPS cells could be a better solution. In this review, we will discuss the interest and the feasibility to establish hPS cells bank, as well as some economics and ethical issues

Natural Killer Cell Alloreactivity Against Human Induced Pluripotent Stem Cells and Their Neuronal Derivatives into Dopaminergic Neurons

In recent years, great hope has arisen surrounding human stem cells, particularly human induced pluripotent stem (hiPS) cells, as nearly all human tissues can be derived from hiPS cells, using a specific protocol. Therefore, hiPS cells can be a source for replacing defective tissues and make up for the lack of organ donors. However, the alloreactivity of hiPS cells and their derivatives in the context of transplantation remain unclear. Although immunosuppressive drugs can inhibit the T cell compartment, these drugs inhibit partially or not at all natural killer (NK) cells activity. Therefore, the alloreactivity of NK cells against transplanted cells remains to be established. To partially answer this question, we choose, as a model, the potential of cellular therapy for Parkinson's disease (PD). First, we established the in vitro derivation of hiPS cells into mature dopaminergic (mDOPA) neurons, going through an intermediate step called neurosphere (NS) cells. These different cells population were cultured with or without interferon gamma (IFN-γ). They were characterized phenotypically regarding their morphology, and the expression of specific ligands for NK cell receptors expressed by these cells types was investigated. NK cells were isolated from the peripheral blood of healthy donors and cultured in the presence of interleukin 15, to be activated. To test NK cell alloreactivity, a cytotoxic assay was performed with hiPS cells, NS cells, and mDOPA neurons (IFN-γ treated or not) cocultured with allogenic NK cells. Our results show that allogenic NK cells kill hiPS cells (IFN-γ treated or not), but IFN-γ-treated NS cells were protected from killing by allogenic NK cells, compared with untreated NS cells. Finally, mDOPA neurons (IFN-γ treated or not) were partially protected against allogenic NK cell killing. These results indicate that derivatives of hiPS cells, especially NS cells, could be a good product for allogenic transplantation in cellular therapy for PD

Blood–Brain Barrier Dynamic Device with Uniform Shear Stress Distribution for Microscopy and Permeability Measurements

Neurology has always been one of the therapeutic areas with higher attrition rates. One of the main difficulties is the presence of the blood–brain barrier (BBB) that restricts access to the brain for major drugs. This low success rate has led to an increasing demand for in vitro tools. The shear stress, which positively affects endothelial cell differentiation by mimicking blood flow, is required for a more physiological in vitro BBB model. We created an innovative device specifically designed for cell culture under shear stress to investigate drug permeability. Our dynamic device encompasses two compartments communicating together via a semi-permeable membrane, on which human cerebral microvascular endothelial (hCMEC/D3) cells were seeded. The fluidic controlled environment ensures a laminar and homogenous flow to culture cells for at least seven days. Cell differentiation was characterized by immunodetection of inter-endothelial junctions directly in the device by confocal microscopy. Finally, we performed permeability assay with lucifer yellow in both static and dynamic conditions in parallel. Our dynamic device is suited to the evaluation of barrier function and the study of drug transport across the BBB, but it could also be used with other human cell types to reproduce intestinal or kidney barriers

Neural progenitors derived from human embryonic stem cells are targeted by allogeneic T and natural killer cells

Neural progenitor cells (NPC) of foetal origin or derived from human embryonic stem cells (HESC) have the potential to differentiate into mature neurons after transplantation into the central nervous system, opening the possibility of cell therapy for neurodegenerative disorders. In most cases, the transplanted NPC are genetically unrelated to the recipient, leading to potential rejection of the transplanted cells. Very few data provide reliable information as to the potential immune response of allogeneic neural progenitors derived from HESC. In this study, we analyzed in vitro the allogeneic immune response of T lymphocytes and natural killer (NK) cells to NPC derived from HESC or of foetal origin. We demonstrate that NPC induce T-cell stimulation and a strong NK cytotoxic response. NK-cell activity is unrelated to MHC-I expression but driven by the activating NKG2D receptor. Cyclosporine and dexamethasone previously used in clinical studies with foetal NPC did not only fail to prevent NK alloreactivity but strongly inhibited the terminal maturation from NPC into mature neurons. We conclude that allogenic transplantation of NPC in the central nervous system will most likely require an immunosuppressive regimen targeting allogenic T and NK cells, whereas possible interference with the differentiation of NPC needs to be carefully evaluated