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Human Induced Pluripotent Stem Cells Are Targets for Allogeneic and Autologous Natural Killer (NK) Cells and Killing Is Partly Mediated by the Activating NK Receptor DNAM-1.

ABSTRACT: Human induced pluripotent stem cells (hiPSCs) could be used to generate autologous cells for therapeutic purposes, which are expected to be tolerated by the recipient. However, iPSC-derived grafts are at risk of giving rise to teratomas in the host, if residuals of tumorigenic cells are not rejected by the recipient. We have analyzed the susceptibility of hiPSC lines to allogeneic and autologous natural killer (NK) cells. IL-2-activated, in contrast to resting NK cells killed hiPSC lines efficiently (P = 1.69 x 10(-39)). Notably, the specific lysis of the individual hiPSC lines by IL-2-activated NK cells was significantly different (P = 1.72 x 10(-6)) and ranged between 46 % and 64 % in 51Cr-release assays when compared to K562 cells. The hiPSC lines were killed by both allogeneic and autologous NK cells although autologous NK cells were less efficient (P=8.63 x 10(-6)). Killing was partly dependent on the activating NK receptor DNAM-1 (P = 8.22 x 10(-7)). The DNAM-1 ligands CD112 and CD155 as well as the NKG2D ligands MICA and MICB were expressed on the hiPSC lines. Low amounts of human leukocyte antigen (HLA) class I proteins, which serve as ligands for inhibitory and activating NK receptors were also detected. Thus, the susceptibility to NK cell killing appears to constitute a common feature of hiPSCs. Therefore, NK cells might reduce the risk of teratoma formation even after autologous transplantations of pluripotent stem cell-derived grafts that contain traces of pluripotent cells.

SUBMITTER: Kruse V

PROVIDER: S-EPMC4423859 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Project description:Natural killer (NK) cells play an important role as cytotoxic effector cells, which scan the organism for infected or tumorigenic cells. Conflicting data have been published whether NK cells can also kill allogeneic or even autologous pluripotent stem cells (PSCs) and which receptors are involved. A clarification of this question is relevant since an activity of NK cells against PSCs could reduce the risk of teratoma growth after transplantation of PSC-derived grafts. Therefore, the hypothesis has been tested that the activity of NK cells against PSCs depends on cytokine activation and specifically on the activating NK receptor NKG2D. It is shown that a subcutaneous injection of autologous iPSCs failed to activate NK cells against these iPSCs and can give rise to teratomas. In agreement with this result, several PSC lines, including two iPSC, two embryonic stem cell (ESC), and two so-called multipotent adult germline stem cell (maGSC) lines, were largely resistant against resting NK cells although differences in killing were found at low level. All PSC lines were killed by interleukin (IL)-2-activated NK cells, and maGSCs were better killed than the other PSC types. The PSCs expressed ligands of the activating NK receptor NKG2D and NKG2D-deficient NK cells from Klrk1-/- mice were impaired in their cytotoxic activity against PSCs. The low-cytotoxic activity of resting NK cells was almost completely dependent on NKG2D. The cytotoxic activity of IL-2-activated NKG2D-deficient NK cells against PSCs was reduced, indicating that also other activating receptors on cytokine-activated NK cells must be engaged by ligands on PSCs. Thus, NKG2D is an important activating receptor involved in killing of murine PSCs. However, NK cells need to be activated by cytokines before they efficiently target PSCs and then also other NK receptors become relevant. These features of NK cells might be relevant for transplantation of PSC-derived grafts since NK cells have the capability to kill undifferentiated cells, which might be present in grafts in trace amounts.

Project description:Dozens of transplants generated from pluripotent stem cells are currently in clinical trials. The creation of patient-specific iPSCs makes personalized therapy possible due to their main advantage of immunotolerance. However, some reports have claimed recently that aberrant gene expression followed by proteome alterations and neoantigen formation can result in iPSCs recognition by autologous T-cells. Meanwhile, the possibility of NK-cell activation has not been previously considered. This study focused on the comparison of autologous and allogeneic immune response to iPSC-derived cells and isogeneic parental somatic cells used for reprogramming. We established an isogeneic cell model consisting of parental dermal fibroblasts, fibroblast-like iPSC-derivatives (iPS-fibro) and iPS-fibro lacking beta-2-microglobulin (B2M). Using the cells obtained from two patients, we analyzed the activation of autologous and allogeneic T-lymphocytes and NK-cells co-cultured with target cells. Here we report that cells differentiated from iPSCs can be recognized by NK-cells rather than by autologous T-cells. We observed that iPS-fibro elicited a high level of NK-cell degranulation and cytotoxicity, while isogeneic parental skin fibroblasts used to obtain iPSCs barely triggered an NK-cell response. iPSC-derivatives with B2M knockout did not cause an additional increase in NK-cell activation, although they were devoid of HLA-I, the major inhibitory molecules for NK-cells. Transcriptome analysis revealed a significant imbalance of ligands for activating and inhibitory NK-cell receptors in iPS-fibro. Compared to parental fibroblasts, iPSC-derivatives had a reduced expression of HLA-I simultaneously with an increased gene expression of major activating ligands, such as MICA, NECTIN2, and PVR. The lack of inhibitory signals might be due to insufficient maturity of cells differentiated from iPSCs. In addition, we showed that pretreatment of iPS-fibro with proinflammatory cytokine IFNγ restored the ligand imbalance, thereby reducing the degranulation and cytotoxicity of NK-cells. In summary, we showed that iPSC-derived cells can be sensitive to the cytotoxic potential of autologous NK-cells regardless of HLA-I status. Thus, the balance of ligands for NK-cell receptors should be considered prior to iPSC-based cell therapies. Trial registration Not applicable.

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Human Induced Pluripotent Stem Cells Are Targets for Allogeneic and Autologous Natural Killer (NK) Cells and Killing Is Partly Mediated by the Activating NK Receptor DNAM-1.

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