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.

Rapid dose-dependent Natural Killer (NK) cell modulation and cytokine responses following human rVSV-ZEBOV Ebolavirus vaccination

The rVSV-ZEBOV Ebolavirus vaccine confers protection within days after immunization, suggesting the contribution of innate immune responses. We report modulation of rVSV-ZEBOV vaccinee blood CD56+ NK cell numbers, NKG2D or NKp30 surface receptor expression, Killer Immunoglobulin-like Receptor (KIR)+ cell percentages and NK-cell-related genes on day 1 post immunization. Inverse correlations existed between the concentration of several plasma cytokines and inhibitory KIR+ CD56dim or cytokine-responsive CD56bright NK cells. Thus, NK cells may contribute to the early protective efficacy of rVSV-ZEBOV in humans.

A significant effect of the killer cell immunoglobulin-like receptor ligand human leucocyte antigen-C on fibrosis progression in chronic C hepatitis with or without liver transplantation

BACKGROUND & AIMS

The interaction of killer cell immunoglobulin-like receptors with their human leucocyte antigen ligands drives the activation and inhibition of natural killer cells. Natural killer cells could be implicated in the development of liver fibrosis in chronic hepatitis C.

METHODS

We analysed 206 non-transplanted and 53 liver transplanted patients, selected according to their Metavir fibrosis stage. Several variables such as the number of activator killer cell immunoglobulin-like receptors or the human leucocyte antigen ligands were considered in multinomial and logistic regression models. Possible confounding variables were also investigated.

RESULTS

The killer cell immunoglobulin-like receptors were not significant predictors of the fibrosis stage. Conversely, a significant reduction of the human leucocyte antigen-C1C2 genotype was observed in the most advanced fibrosis stage group (F4) in both cohorts. Furthermore, the progression rate of fibrosis was almost 10 times faster in the subgroup of patients after liver transplantation, and human leucocyte antigen-C1C2 was significantly reduced in this cohort compared with non-transplanted patients.

CONCLUSION

This study suggests a possible role of killer cell immunoglobulin-like receptors and their ligands in the development of liver damage. The absence of C1 and C2 ligands heterozygosity could lead to less inhibition of natural killer cells and a quicker progression to a high level of fibrosis in patients infected with hepatitis C virus, especially following liver 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.

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.

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.

Activating CD94:NKG2C and inhibitory CD94:NKG2A receptors are expressed by distinct subsets of committed CD8+ TCR alphabeta lymphocytes

A subset of CD8(+) T cells express the natural killer cell receptors CD94:NKG2A or CD94:NKG2C. We found that although many CD8(+) T cells transcribe CD94 and NKG2C, expression of a functional CD94:NKG2C receptor is restricted to highly differentiated effector cells. CD94:NKG2A is expressed by a different subset consisting of CCR7(+) memory cells and CCR7(-) effector cells. Since NKG2A can only be induced on naive CD8(+) T cells while CD94(-) memory cells are refractory, it is likely that commitment to the CD94:NKG2A(+) subset occurs during the first encounter with antigen. CCR7(+)CD94:NKG2A(+) T cells recirculate through lymph nodes where upon activation, they produce large quantities of IFN-gamma. These cells occur as a separate CD94:NKG2A(+) T cell lineage with a distinct TCR repertoire that differs from that of the other CD8(+)CD94(-) T cells activated in situ.