Natural killer cell-activating receptor NKG2D mediates innate immune targeting of allogeneic neural progenitor cell grafts.

Cell replacement therapy holds promise for a number of untreatable neurological or psychiatric diseases but the immunogenicity of cellular grafts remains controversial. Emerging stem cell and reprogramming technologies can be used to generate autologous grafts that minimize immunological concerns but autologous grafts may carry an underlying genetic vulnerability that reduces graft efficacy or survival. Healthy allogeneic grafts are an attractive and commercially scalable alternative if immunological variables can be controlled. Stem cells and immature neural progenitor cells (NPC) do not express major histocompatibility complex (MHC) antigens and can evade adaptive immune surveillance. Nevertheless, in an experimental murine model, allogeneic NPCs do not survive and differentiate as well as syngeneic grafts, even when traditional immunosuppressive treatments are used. In this study, we show that natural killer (NK) cells recognize the lack of self-MHC antigens on NPCs and pose a barrier to NPC transplantation. NK cells readily target both syngeneic and allogeneic NPC, and killing is modulated primarily by NK-inhibiting "self" class I MHC and NK-activating NKG2D-ligand expression. The absence of NKG2D signaling in NK cells significantly improves NPC-derived neuron survival and differentiation. These data illustrate the importance of innate immune mechanisms in graft outcome and the potential value of identifying and targeting NK cell-activating ligands that may be expressed by stem cell derived grafts.

NKG2C/KLRC2 tumor cell expression enhances immunotherapeutic efficacy against glioblastoma.

BACKGROUND: Activating and inhibitory receptors of natural killer (NK) cells such as NKp, NKG2, or CLEC are highly relevant to cold tumors including glioblastoma (GBM). Here, we aimed to characterize the expression of these receptors in GBM to gain insight into their potential role as modulators of the intratumoral microenvironment. METHODS: We performed a transcriptomic analysis of several NK receptors with a focus on the activating receptor encoded by KLRC2, NKG2C, among bulk and single-cell RNA sequencing GBM data sets. We also evaluated the effects of KLRC2-overexpressing GL261 cells in mice treated with or without programmed cell death protein-1 (PD-1) monoclonal antibody (mAb). Finally, we analyzed samples from two clinical trials evaluating PD-1 mAb effects in patients with GBM to determine the potential of NKG2C to serve as a biomarker of response. RESULTS: We observed significant expression of several inhibitory NK receptors on GBM-infiltrating NK and T cells, which contrasts with the strong expression of KLRC2 on tumor cells, mainly at the infiltrative margin. Neoplastic KLRC2 expression was associated with a reduction in the number of myeloid-derived suppressor cells and with a higher level of tumor-resident lymphocytes. A stronger antitumor activity after PD-1 mAb treatment was observed in NKG2Chigh-expressing tumors both in mouse models and patients with GBM whereas the expression of inhibitory NK receptors showed an inverse association. CONCLUSIONS: This study explored the role of neoplastic NKG2C/KLRC2 expression in shaping the immune profile of GBM and suggests that it is a predictive biomarker for positive responses to immune checkpoint inhibitor treatment in patients with GBM. Future studies could further validate this finding in prospective trials.

Specific alterations in NKG2D+ T lymphocytes in relapsing-remitting and progressive multiple sclerosis patients.

BACKGROUND: T lymphocytes exhibit numerous alterations in relapsing-remitting (RRMS), secondary progressive (SPMS), and primary progressive multiple sclerosis (PPMS). The NKG2D pathway has been involved in MS pathology. NKG2D is a co-activating receptor on subsets of CD4+ and most CD8+ T lymphocytes. The ligands of NKG2D are expressed at low levels in normal tissues but are elevated in MS postmortem brain tissues compared with controls. Whether the NKG2D pathway shows specific changes in different forms of MS remains unclear. METHODS: We performed unsupervised and supervised flow cytometry analysis to characterize peripheral blood T lymphocytes from RRMS, SPMS, and PPMS patients and healthy controls (HC). We used an in vitro microscopy approach to assess the role of NKG2D in the interactions between human CD8+T lymphocytes and human astrocytes. RESULTS: Specific CD8+, CD4+, and CD4-CD8- T cell populations exhibited altered frequency in MS patients' subgroups. The proportion of NKG2D+ T lymphocytes declined with age in PPMS patients but not in RRMS and HC. This reduced percentage of NKG2D+ cells was due to lower abundance of γδ and αß CD4-CD8- T lymphocytes in PPMS patients. NKG2D+ T lymphocytes were significantly less abundant in RRMS than in HC; this was caused by a decreased frequency of CD4-CD8- and CD8+ T lymphocytes and was not linked to age. Blocking NKG2D increased the motility of CD8+ T lymphocytes co-cultured with astrocytes expressing NKG2D ligand. Moreover, preventing NKG2D from interacting with its ligands increased the proportion of CD8+ T lymphocytes exhibiting a kinapse-like behavior characterized by short-term interaction while reducing those displaying a long-lasting synapse-like behavior. These results support that NKG2D participates in the establishment of long-term interactions between activated CD8+ T lymphocytes and astrocytes. CONCLUSION: Our data demonstrate specific alterations in NKG2D+ T lymphocytes in MS patients' subgroups and suggest that NKG2D contributes to the interactions between human CD8+ T lymphocytes and human astrocytes.

Expression and clinical significance of the NK cell-activating receptor NKG2D and its ligand in liver tissue of patients with primary biliary cholangitis / 临床肝胆病杂志

ObjectiveTo investigate the association of the expression of the NK cell-activating receptor NKG2D, its ligand major histocompatibility complex class I chain-related gene A (MICA), and related cytokines ［interferon-γ (IFN-γ), interleukin-10 (IL-10), and interleukin-15 (IL-15)］ with intrahepatic inflammation in primary biliary cholangitis (PBC). MethodsLiver biopsy specimens were collected from 30 patients with PBC (PBC group), 15 patients with chronic hepatitis B (CHB group), and 10 patients with nonalcoholic fatty liver disease (NAFLD group), who were hospitalized in The Second Affiliated Hospital of Kunming Medical University from August 2014 to June 2015. The degree of liver inflammation (G) and fibrosis degree (S) of the liver specimens were determined, and immunohistochemistry was used to measure the expression of NKG2D, MICA, IFN-γ, IL-10, and IL-15 in liver tissue (the scores were determined based on the number of cells stained and the degree of staining to evaluate the expression of each marker). A one-way analysis of variance was used for comparison of continuous data between multiple groups, and the t-test was used for comparison between two groups; a Spearman correlation analysis was used to investigate correlation. ResultsIn the PBC group, the expression of NKG2D increased with the degree of inflammation, and the patients with G3-4 inflammation had significantly higher expression than those with G1-2 inflammation (G1 vs G2 vs G3 vs G4: 1.4±0.05 vs 1.56±0.05 vs 1.86±0.11 vs 2.60±0.17, F=150.8, P＜0.05); the expression of NKG2D decreased with fibrosis degree (S3 vs S4: 2.30±0.17 vs 1.56±0.05, t=-1.52, P＜0.05). In the PBC group, there was no significant difference in MICA between G3 and G4 (0.11±0.01 vs 0.20±0.03, t=-2.20, P＞0.05) and between S3 and S4 (0.12±0.02 vs 0.18±0.03, t=-2.64, P＞0.05). In the PBC group, there was a significant difference in the expression of IL-15 between the patients with different degrees of inflammation (G1 vs G2 vs G3 vs G4: 0.70±0.10 vs 1.50±0.10 vs 1.93±0.11 vs 2.60±0.17, F=251.3, P＜0.05), while there was no significant difference between the patients with different fibrosis degrees (S3 vs S4: 2.00±0.05 vs 2.40±0.30, t=-1.62, P＞0.05). In the CHB group, there was a significant difference in the expression of IL-15 between the patients with different degrees of inflammation (G1 vs G2 vs G3: 0.73±0.15 vs 1.96±0.15 vs 2.50±0.17, F=150, P＜0.05) and between the patients with different fibrosis degrees (S1 vs S2 vs S3: 0.70±0.10 vs 21.96±0.15 vs 2.50±0.17, F=158.7, P＜0.05). In the PBC group, the expression of IL-10 was only observed in the patients with G1 inflammation (0.16±0.01), and in the CHB group, the expression of IL-10 was observed in the patients with G1 and G2 inflammation, with no significant difference (G1 vs G2: 0.19±0.01 vs 0.13±0.01, t=-1.522, P＞0.05). In the patients with PBC, the expression of IL-15 in liver tissue was positively correlated with the levels of alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (GGT) (r=0.241 and 0.407, P=0.014 and 0.045). ConclusionThe NK cell-activating receptor NKG2D affects the degree of intrahepatic inflammation in PBC, and the NKG2D ligand MICA is expressed in the advanced stage of PBC and can downregulate NKG2D. The expression of IL-15 increases with the degree of inflammation in PBC and is positively correlated with the levels of ALP and GGT, suggesting that the activation of NK cells and abnormal secretion of cytokines are involved in the development and progression of PBC and IL-15 may be used as an auxiliary index for the diagnosis of PBC.

The study of major histocompatibility complex class Ⅰ related genes expression in colonic mucosa tissue and the correlation with ulcerative colitis / 中华消化杂志

Objective To investigate the function of major histocompatibility complex (MHC)class Ⅰ-related gene (MIC) in ulcerative colitis (UC) pathogenesis. Methods The difference of MICA, M ICB and their ligand NKG2D genes expression in colonic mucosa tissue of 34 UC patients and 12 healthy people were determined by fluorescent real-time reverse-transcriptase polymerase chain reaction (RT-PCR) and the expression location of M ICA in colonic mucosa tissue was obtained by laser scanning confocal microscope. Results The mRNA level of MICA, MICB and NKG2D expression in UC groups (3. 5408±2. 6658, 8. 9879±3. 2893 and 2. 4395±0. 8147 accordingly) was significantly higher than that in the healthy controls ( 1. 0477 ± 0. 7201, 4. 6293 ± 1. 2616 and 1. 1624±0. 3954 accordingly) (P = 0.0053, 0.0039 and 0. 0078 accordingly). It suggested that MICA was expressed in colonic epithelia cell membranes by laser scanning confocal microscopy.Conclusion The mRNA level of MICA, M ICB, and their ligand, NKG2D expression were all up regulated in the colonic mucosa of UC patients, which indicated MIC gene might perform important local function in UC.

Nickel induces secretion of IFN-gamma by splenic natural killer cells

Although nickel hypersensitivity is known as a delayed-type hypersensitivity mediated by nickel-specific T cells, it is greatly influenced by other immune cells. Here we show that splenic natural killer cells (NK cells) directly or indirectly respond to nickel by secretion of IFN-gamma. Using enzyme-linked immunosorbent spot (ELISPOT) assays, we found that nickel-reactive cells readily secreted IFN-gamma when splenocytes were cultured in the presence of varying concentrations of nickel sulfate (NiSO4) for 24 h. However, nickel-reactive IL-2- or IL- 4-secreting cells were infrequent during the 24-h culture with NiSO4. Immune responses to nickel were innate, not adaptive, in nature since the frequency of nickel-reactive IFN-gamma-secreting cells did not increase upon previous exposure to NiSO4 and recombination activating gene (RAG)-1-deficient mice contained nickel-reactive IFN-gamma-secreting cells. The involvement of NK cells in the innate response to NiSO4 was confirmed since we could observe a significant reduction of the frequency of nickel-reactive cells in NK cell-depleted mice. Furthermore, the number of IFN-gamma secreting cells was significantly reduced in the ELISPOT assays when NKG2D was blocked by anti-NKG2D antibody. These results suggest that there is an early and rapid innate immune response to nickel, which is mediated by NK cells and the NKG2D receptor. The significance of the innate response to nickel is that it may contribute to development of the late T cell-mediated delayed type hypersensitivity against nickel.