Regulation Of Natural Killer Cell Activity Research Articles

Chemerin and the recruitment of NK cells to diseased skin.

Natural killer (NK) cells play a major role in the initial control of many viral pathogens and in the rejection of tumors. Consistent with their roles as immune sentinels, NK cells are found in inflamed skin, including lichen planus, psoriasis and atopic dermatitis (AD) lesions. In oral lichen planus lesions, the recruitment as well as intradermal colocalization of NK cells and pDC (plasmacytoid dendritic cells) appear to be mediated by chemerin, a recently identified protein ligand for chemokine-like receptor 1 (CMKLR1), a chemoattractant receptor expressed by both cell types. Dendritic cells can regulate NK cell activity, and NK cells can regulate DC-mediated responses. Since chemerin was recently implicated in recruitment of pDC to psoriatic skin, in this work we determined whether chemerin facilitates interactions between NK and pDC in psoriatic plaques through controlling influx of NK cells to diseased skin. We demonstrate that circulating NK cells from normal donors as well as psoriasis and AD patients respond similarly in functional migration assays to chemerin. However, differences in the distribution of NK cells and pDC in skin lesions suggest that recruitment of both NK cells and pDC is unlikely to be controlled solely by chemerin.

Post-transcriptional Regulation of NK Cell Activation

Natural killer (NK) cells play key roles in innate and adaptive immune defenses. NK cell responses are mediated by two major mechanisms: the direct cytolysis of target cells, and immune regulation by production of various cytokines. Many previous reports show that the complex NK cell activation process requires de novo gene expression regulated at both transcriptional and post-transcriptional levels. Specialized un-translated regions (UTR) of mRNAs are the main mechanisms of post-transcriptional regulation. Analysis of post-transcriptional regulation is needed to clearly understand NK cell biology and, furthermore, harness the power of NK cells for therapeutic aims. This review summarizes the current understanding of mRNA metabolism during NK cell activation, focusing primarily on post-transcriptional regulation.

Up on the tightrope: natural killer cell activation and inhibition.

Natural killer (NK) cells circulate through the blood, lymphatics and tissues, on patrol for the presence of transformed or pathogen-infected cells. As almost all NK cell receptors bind to host-encoded ligands, signals are constantly being transmitted into NK cells, whether they interact with normal or abnormal cells. The sophisticated repertoire of activating and inhibitory receptors that has evolved to regulate NK cell activity ensures that NK cells protect hosts against pathogens, yet prevents deleterious NK cell-driven autoimmune responses. Here I highlight recent advances in our understanding of the structural properties and signaling pathways of the inhibitory and activating NK cell receptors, with a particular focus on the ITAM-dependent activating receptors, the NKG2D-DAP10 receptor complexes and the CD244 receptor system.

NK-Cell Reconstitution after HLA-Identical Blood and Marrow Transplantations for CML: The Recovery of NKG2D Is Inversely Correlated with NKG2A and It Promotes the GVL Effect.

Natural killer (NK) cell alloreactivity is reported to mediate strong graft versus leukemia (GVL) effect in patients after allogeneic stem-cell transplantation. NKG2D receptors recognize human MHC class Ichain related A and B (MICA/B) and UL16-binding protein 1∼4(ULBP 1∼4) on target cells, thereby regulating NK cell activity. To examine the recovery of NKG2D, NKG2A and other receptors expression by NK cells, we used flow cytometry to evaluate samples from 11 chronic myeloid leukemia patients and their donors in the year following unmanipulated HLA completely matched peripheral blood stem cells plus bone marrow transplantation. Peripheral blood mononuclear cells from patients and their donors were tested in standard 51Cr release assays against cultured K562 targets to determine the cytotoxicity of the NK cells in the same intervals. There is no mismatched immunoglobulin-like receptor (KIR) ligand in both GVH and HVG direction. The reconstitution of KIR2DL1 (CD158a) after this transplantation protocol was very slow and these receptors didn't reach normal value in the year and KIR2DL2 (CD158b) was much better. The NKG2D increased and the NKG2A decreased quickly at the same time after engraftment, and used linear regression analysis we demonstrated that NKG2A recovery was inversely correlated with NKG2D recovery in the year following transplantation. The ratio of NKG2D/NKG2A was directly associated with the capacity of NK-cell cytotoxicity. Thus, the reconstitution of NKG2D makes contribution to the recovery of the NK cytotoxicity. These results reveals that the NK cells generated after HLA matched blood plus bone morrow transplantation of CML patients are promoted at an immature state characterized by specific phenotypic features and enhanced functioning, having potential impact for immune responsiveness and transplantation outcome.

Reconstitution of Natural Killer Cell Receptor Repertoires after Unmanipulated HLA-Mismatched/Haploidentical Blood and Marrow Transplantation: Analyses of CD94:NKG2A and Killer Immunoglobulin-Like Receptor Expression and Their Associations with Clinical Outcome

The effect of natural killer (NK) cell alloreactivity on the outcome of haploidentical hematopoietic stem cell transplantation (HSCT), with or without in vitro T cell depletion, remains controversial. Killer immunoglobulin-like receptors (KIRs) recognize human leukocyte antigen C and B epitopes on target cells, thereby regulating NK cell activity. To examine the recovery of CD94:NKG2A and KIR (CD158a, CD158b, and CD158e) expression by NK cells, we used flow cytometry to evaluate samples from 24 patients and their donors before and in the year following unmanipulated HLA-haploidentical/mismatched blood and marrow transplantation. Linear regression analysis demonstrated that NKG2A recovery was inversely correlated with CD158b recovery in the year following transplant. The doses of T cell subgroups CD4 + and CD8 + were inversely associated with CD158a and CD158e expression during the 2 months following transplantation. Moreover, patients with grades II-IV acute graft-versus-host disease (aGVHD) or who received “high” doses of T cells (>1.37 × 10 8/kg) showed delayed recovery of KIRs during the 2 months following transplantation. Univariate analysis showed that patients with high CD94 expression by day 60 (>90%) or who received donors with high CD94 expression (>80%) were associated with higher transplantation-related mortality ( P = .006 or .067, respectively) and poorer leukemia-free survival ( P = .012 or .094, respectively). Thus, the occurrence of aGVHD or the receipt of high doses of T cells in the allograft altered KIR reconstitution. Furthermore, high levels of CD94 expression in donors or in recipients by day 60 might be a good predictor for poor prognosis.

226: Differential requirement for NKG2D in the rejection of haplomismatched and MHC-I deficient bone marrow

Mouse Natural Killer (NK) cells mediate rejection of MHC-mismatched or MHC-deficient bone marrow allografts. Counteracting activating and inhibitory signals regulate NK cell activity. The ability of F1 mice to reject parental bone marrow (BM) cells (hybrid resistance) has been attributed to the presence in the recipient of a subset of NK cells that lack inhibitory receptors for the MHC class I antigens expressed by the donor cells. Evidence supporting the “missing self” hypothesis of hybrid resistance was provided by demonstration that MHC class-I deficient donor BM is rejected by otherwise syngeneic recipients. We have previously demonstrated a role for NKG2D, an activating NK cell receptor, in rejection of Balb/c (H-2d) parental BM by (Balb/c x C57Bl/6; H-2b/d) F1 (CB6F1) recipient mice. NKG2D ligands are expressed on the regenerating myeloid BM cells in Balb/c and NOD mice but not substantially on the regenerating C57Bl/6 BM cells. Moreover, the rejection of Balb/c BM by CB6F1 recipients was blocked by a neutralizing anti-NKG2D monoclonal antibody. The purpose of this study was to determine whether NKG2D blockade was sufficient to prevent rejection of MHC-I deficient BM. Beta-2 microglobulin deficient (B2M-/-) Balb/c or NOD bone marrow was transplanted into irradiated CB6F1 mice that had been pretreated with neutralizing antibodies to NKG2D. In contrast to results with wild-type Balb/c or NOD BM whose rejection was prevented by anti-NKG2D, B2M-/- donor cells were rejected despite NKG2D blockade. Furthermore, syngeneic MHC class I+ Balb/c recipients were able to reject B2M-/- Balb/c donors despite NKG2D blockade. These results suggest that rejection of MHC class I-bearing BM requires activation via NKG2D, whereas MHC class I-deficient BM elicit a sufficiently strong NK response that augmentation by NKG2D signaling is not essential for the rejection. Therefore, the hybrid resistance model in which MHC class I-bearing BM are used for transplantation may better reflect the situation in human hematopoietic stem cell transplantation. Mouse Natural Killer (NK) cells mediate rejection of MHC-mismatched or MHC-deficient bone marrow allografts. Counteracting activating and inhibitory signals regulate NK cell activity. The ability of F1 mice to reject parental bone marrow (BM) cells (hybrid resistance) has been attributed to the presence in the recipient of a subset of NK cells that lack inhibitory receptors for the MHC class I antigens expressed by the donor cells. Evidence supporting the “missing self” hypothesis of hybrid resistance was provided by demonstration that MHC class-I deficient donor BM is rejected by otherwise syngeneic recipients. We have previously demonstrated a role for NKG2D, an activating NK cell receptor, in rejection of Balb/c (H-2d) parental BM by (Balb/c x C57Bl/6; H-2b/d) F1 (CB6F1) recipient mice. NKG2D ligands are expressed on the regenerating myeloid BM cells in Balb/c and NOD mice but not substantially on the regenerating C57Bl/6 BM cells. Moreover, the rejection of Balb/c BM by CB6F1 recipients was blocked by a neutralizing anti-NKG2D monoclonal antibody. The purpose of this study was to determine whether NKG2D blockade was sufficient to prevent rejection of MHC-I deficient BM. Beta-2 microglobulin deficient (B2M-/-) Balb/c or NOD bone marrow was transplanted into irradiated CB6F1 mice that had been pretreated with neutralizing antibodies to NKG2D. In contrast to results with wild-type Balb/c or NOD BM whose rejection was prevented by anti-NKG2D, B2M-/- donor cells were rejected despite NKG2D blockade. Furthermore, syngeneic MHC class I+ Balb/c recipients were able to reject B2M-/- Balb/c donors despite NKG2D blockade. These results suggest that rejection of MHC class I-bearing BM requires activation via NKG2D, whereas MHC class I-deficient BM elicit a sufficiently strong NK response that augmentation by NKG2D signaling is not essential for the rejection. Therefore, the hybrid resistance model in which MHC class I-bearing BM are used for transplantation may better reflect the situation in human hematopoietic stem cell transplantation.

Cytokine-Activated Natural Killer Cells Exert Direct Killing of Hepatoma Cells Harboring Hepatitis C Virus Replicons

Hepatitis C virus (HCV)-specific impairments in host immunity have been described at multiple levels of the innate and adaptive response, which may lead to viral persistence in the majority of infections. Understanding of HCV-associated immune defects could lead to novel therapeutic advances. Natural killer (NK) cells, the major effector cells of the innate immune system, are functionally impaired in chronic HCV infection. It has been suggested that this phenotype is a result of virus-specific defects in antigen-presenting cells (APCs) that regulate NK cell activity, as normal NK function is restored when they are stimulated ex vivo. In this study, we used human NK cell cytotoxicity assays to evaluate the activation-induced effects of NK cells on the HCV replicon-containing hepatic cells. We found that cytokine-activated NK cells were capable of inducing an HCV-associated, perforin/granzyme-dependent lysis of human hepatoma cells and that this required direct cellular contact and was independent of MHC class I expression levels. In contrast, on removal of cytokine stimulation, NK cells failed to exert any direct cytolytic effect on replicon targets. These findings suggest an important underlying mechanism by which NK cells control HCV infection and, with appropriate understanding of HCV-associated immune defects, could lead to novel therapeutic advances.

Tumor Cell-Derived HLA-B-Associated Transkript 3 (BAT3) Is a Ligand for NKp30 and Activates NK Cells.

Natural-killer (NK)-cells are lymphocytes of the innate immune system, which directly attack tumor and virus-infected cells. They provide a link between innate and adaptive immunity through crosstalk with dendritic cells (DCs) and mediate T-cell activation. Among the activating and inhibitory receptors that regulate NK cell activity, the orphan NKp30 receptor (NCR3, CD337) plays a special role as NKp30 does not only induce target cell lysis but is also crucial for the interaction between NK cells and dendritic cells. However, so far the cellular ligands for NKp30 have remained elusive.Using a yeast two hybrid approach with the extracellular NKp30 sequence as bait we were able to isolate a putative NKp30 ligand from a tumor cDNA library. Sequence analysis revealed that the cDNA encoded for BAT3 (HLA-B-associated transcript 3) which originally had been cloned from the human major histocompatibility complex by chromosome walking and mapped to chromosome 6p21.3 within the HLA complex. BAT3 was described as a nuclear protein characterized by an N-terminal ubiquitin-like region, a polyproline stretch and a highly conserved BAG-(Bcl-2-associated athanogene) domain. Until now, the function of BAT3 in mammals is not clearly defined. With BAT3-specific antibodies and by means of laser scanner microscopy and Western Blotting we demonstrate that tumor cell lines and immature as well as mature DCs express BAT3. Upon co-cultivation with NK cells or exposure to stress signals such as heat shock, we observed that BAT3 translocates from the nucleus to the cell-surface and the protein is released from tumor cells into the extracellular environment. BAT3 binds directly and specifically to NKp30 on NK cells and triggers NK cell-mediated cytokine release and NKp30-dependent cytotoxicity. The inhibition of endogenous BAT3 using polyclonal antibodies prevents tumor rejection in vivo, demonstrating that BAT3 is necessary for the tumor rejection in a xenograft tumor model.Thus, BAT3 is the long sought cellular NKp30 ligand and exhibits a novel mechanism by which a nuclear protein activates NK cells via NKp30-engagement after its release to the cell-surface and the cell environment. The isolation of the first cellular NKp30-ligand provides the basis for a better molecular understanding of NK cell-regulation and allows the development of clinical applications targeting NKp30 for the immunotherapy.

Low Number of Donor Activating Killer Immunoglobulin-Like Receptors (KIR) Genes but not KIR-Ligand Mismatch Prevents Relapse and Improves Disease-Free Survival in Leukemia Patients After In Vivo T-Cell Depleted Unrelated Stem Cell Transplantation

The effect of natural killer (NK) cell alloreactivity on outcome of unrelated stem cell transplantation (SCT) remains controversial. Killer immunoglobulin-like receptors (KIRs) recognize human leukocyte antigen C and B epitopes on target cells, thereby regulating NK cell activity. The KIR genes are polymorphic and two broad haplotypes exist: KIR-haplotype A mainly encode for inhibitory receptors and only for one activating (KIR2DS4), whereas the group B haplotype encodes more for activating KIRs (KIR2DS1, KIR2DS2, KIR2DS3, KIR2DS5 und KIR3DS1). The impact of KIR ligand mismatch on the number of activating and inhibitory donor KIR genes and on KIR-haplotype was studied on outcome of 142 patients with leukemia, who received standard myeloablative conditioning followed by in vivo T-cell depleted (ATG) unrelated SCT. In a multivariate analysis KIR ligand mismatch had significantly higher treatment related mortality (RR 2.206, P = 0.03), resulting in reduced overall (RR 2.015, P = 0.02) and disease-free survival (RR 1.924, P = 0.03). In contrast, SCT from donors with group A haplotype (P = 0.003) or with low number of activating KIR genes (P = 0.005) resulted in reduced relapse rate with improved disease-fee survival (P = 0.04). This effect was seen only in acute myeloid leukemia/myelodysplastic syndrome and to a less extent in chronic myeloid leukemia. No effect was seen for acute lymphoblastic leukemia. After in vivo T-cell depleted (ATG) unrelated stem cell transplantation with donors carrying low number of activating KIR genes (group A KIR haplotype), the risk of relapse is reduced and resulted in a significantly better disease-free survival.

Formation of a WIP-, WASp-, actin-, and myosin IIA–containing multiprotein complex in activated NK cells and its alteration by KIR inhibitory signaling

The tumor natural killer (NK) cell line YTS was used to examine the cytoskeletal rearrangements required for cytolysis. A multiprotein complex weighing ∼1.3 mD and consisting of WASp-interacting protein (WIP), Wiskott-Aldrich syndrome protein (WASp), actin, and myosin IIA that formed during NK cell activation was identified. After induction of an inhibitory signal, the recruitment of actin and myosin IIA to a constitutive WIP–WASp complex was greatly decreased. Both actin and myosin IIA were recruited to WIP in the absence of WASp. This recruitment correlated with increased WIP phosphorylation, which was mediated by PKCθ. Furthermore, the disruption of WIP expression by WIP RNA interference prevented the formation of this protein complex and led to almost complete inhibition of cytotoxic activity. Thus, the multiprotein complex is important for NK cell function, killer cell immunoglobulin-like receptor inhibitory signaling affects proteins involved in cytoskeletal rearrangements, and WIP plays a central role in the formation of the complex and in the regulation of NK cell activity.

Incompatible Inhibitory KIR Ligands Contribute To Lower Survival Rates in Leukemia Patients Receiving T-Replete Hematopoietic Cell Transplants (HCTs).

Natural killer (NK) cells are becoming increasingly recognized as an important part of the immune system. Killer Ig-like receptors (KIRs) are the major form of receptors used by human NK cells. KIRs transmit either inhibitory or activating signals regulating NK cell activity. Some inhibitory KIRs specifically recognize HLA-A, B or -Cw allotypes on target cells. Thus differences in inhibitory ligand (iKIRL) phenotypes between donors and patients could result in NK cell alloreactivity that further results in different HCT outcomes. To test this hypothesis, the present study evaluated 362 patients with either ALL (99), AML/MDS (141), or CML (122). The patients were transplanted (1996~2003) with T-replete bone marrow, or peripheral blood stem cells from unrelated donors. High resolution HLA typing with DNA-based methods had been prospectively performed for donor selection. The KIR genes of patients and donors were retrospectively typed by a multiplex PCR-SSP method. The cohort was divided into three groups by the HLA and KIR profiles: 247 cases with matched HLA at the antigen level of HLA-A, B, Cw, DRB1, and DQB1 (MH), 64 with mismatched HLA (mMH) and 51 with mMH plus mismatched iKIRL (mMH+miKIRL). A significantly different rate (P=0.009) of estimated one year overall survival was found between the MH (61%, 95%CI 55–67%), the mMH (46%, 34–59%), and the mMH+miKIRL (29%, 18–43%) groups. When analyzing the event free survival, a similar difference (P=0.003) was observed between the MH (57%, 51–63%), the mMH (43%, 32–56%) and the mMH+miKIRL (25%, 15–39%) groups. Further analysis demonstrated a different rate (P=0.02) of relapse between the MH (two-year estimation: 21%, 16–28%), the mMH (16%, 7–31%), and the mMH+miKIRL (36% 18–58%) groups. That the MH group experienced more relapses than the mMH is consistent with the GvL effect. The mMH+miKIRL group experienced the most relapses implied miKIRL undermine the GvL effect. We also tested the influence of lacking iKIRL in patients within the MH group, and found a significant survival difference (P=0.05) among the patients lacking two iKIRLs (n=67, 54% 42%–65%), one iKIRL (n=104, 59% 49%–68%), or none (n=76, 70% 58%–79%). This finding contrasts with the previously reported beneficial role of potential NK cell alloreactivity in T-depleted HCT. Additional studies are required to resolve these issues.

BCR/ABL Promotes Dendritic Cell–Mediated Natural Killer Cell Activation

BCR/ABL fusion gene, encoding a paradigmatic tyrosine kinase involved in chronic myelogenous leukemia (CML), can modulate the expression of genes involved in natural killer (NK) cell target recognition. Recent reports outline the role of allogeneic antileukemic NK effectors in the graft-versus-leukemia effect but the regulation of NK cell activation in the setting of graft-versus-leukemia effect remains unknown. Here we show that dendritic cells derived from monocytes of CML patients are selectively endowed with NK cell stimulatory capacity in vitro. We further show, using a gene transfer approach in mouse bone marrow progenitors, that ABL/ABL is necessary to promote dendritic cell-mediated NK cell activation. The dendritic cell/NK cell cross-talk in ABL/ABL-induced CML seems unique because JunB or IFN consensus sequence binding protein loss of functions, associated with other myeloproliferative disorders, do not promote dendritic cell-mediated NK cell activation. NK cell activation by leukemic dendritic cells involves NKG2D activating receptors and is blocked by imatinib mesylate. Indeed, ABL/ABL translocation enhances the expression levels of the NKG2D ligands on dendritic cells, which is counteracted by imatinib mesylate. Altogether, the clonal ABL/ABL dendritic cells display the unique and selective ability to activate NK cells and may participate in the NK cell control of CML. This study also highlights the deleterious role of imatinib mesylate at the dendritic cell level for NK cell activation.

Negative Regulation of T Cell Receptor Signaling by Siglec-7 (p70/AIRM) and Siglec-9

Siglec-7 (p70/AIRM) and Siglec-9 are "CD33"-related siglecs expressed on natural killer (NK) cells and subsets of peripheral T cells. Like other inhibitory NK cell receptors, they contain immunoglobulin receptor family tyrosine-based inhibitory motifs in their cytoplasmic domains, and Siglec-7 has been demonstrated to negatively regulate NK cell activation. Based on reports of the presence of these siglecs on T cells, we sought to determine if they are capable of modulating T cell receptor (TCR) signaling using Jurkat T cells stably and transiently transfected with Siglec-7 or Siglec-9. Following either pervanadate stimulation or TCR engagement, both Siglecs exhibited increased tyrosine phosphorylation and recruitment of SHP-1. Effects of Siglec-7 and -9 were also evident in downstream events in the signaling pathway. Both siglecs reduced phosphorylation of Tyr319 on ZAP-70, known to play a pivotal role in up-regulation of gene transcription following TCR stimulation. There was also a corresponding decreased transcriptional activity of nuclear factor of activated T cells (NFAT) as determined using a luciferase reporter gene. Like all siglecs, Siglec-7 and -9 recognize sialic acid-containing glycans of glycoproteins and glycolipids as ligands. Mutation of the conserved Arg in the ligand binding site of Siglec-7 (Arg124) or Siglec-9 (Arg120) resulted in reduced inhibitory function in the NFAT/luciferase transcription assay, suggesting that ligand binding is required for optimal inhibition of TCR signaling. The combined results demonstrate that both Siglec-7 and Siglec-9 are capable of negative regulation of TCR signaling and that ligand binding is required for optimal activity.

Activation of natural killer cells: underlying molecular mechanisms revealed.

Natural killer (NK) cells, the third major lymphocyte population, are important effector cells against certain infections and tumours. They have also been implicated as a link between innate and adaptive immune responses. In recent years, much attention has been paid to the NK cell inhibitory receptors and their interaction with major histocompatibility complex class I molecules on target cells. This review summarizes recent findings on regulation of NK cell activity with an emphasis on NK cell stimulatory receptors. A particular emphasis is devoted to the receptor NKG2D that is expressed on all NK cells.

Role of IFN-alpha/beta and IL-12 in the activation of natural killer cells and interferon-gamma production during experimental infection with Trypanosoma cruzi.

Control of Trypanosoma cruzi infection depends largely upon the production of interferon (IFN)-gamma. During experimental infection this cytokine is produced early, mainly by natural killer (NK) cells and later by T cells. As NK cells have been reported to participate in defence against T. cruzi, it is of importance to study the regulation of NK cell functions during infection with the parasite. Several innate cytokines regulate NK cell activity, among them being interferon (IFN)-alpha and IFN-beta (type 1 IFNs) and interleukin (IL)-12, which have all been reported to be involved in protection against T. cruzi. The role of these cytokines in regulation of NK cell functions and disease outcome were studied by infection of mutant mice lacking the IFN-alpha/beta receptor (IFNalpha/betaR-/-) or IL-12 (IL-12-/-) with T. cruzi. IFNalpha/betaR-/- mice were unable to activate the cytotoxic response but produced IFN-gamma, and were not more susceptible than controls. IL-12-/- mice were extremely susceptible and failed to produce T cell-derived IFN-gamma and nitric oxide (NO), although NK cytotoxicity was induced. The results indicate that IL-12 protects against T. cruzi by initiating T cell-mediated production of IFN-gamma, but that endogenous IFN-alpha/beta and NK cell cytotoxicity are not of major importance in defence.

Natural Killer Cells Express Estrogen Receptor-α and Estrogen Receptor-β and Can Respond to Estrogen Via a Non-Estrogen Receptor-α-Mediated Pathway

Natural killer (NK) cells play a crucial role in host defense against pathogens and immune surveillance against cancer. Given that estrogens have been reported to suppress NK cell activity, we sought to elucidate the mechanisms by which estrogen mediates this effect. We demonstrate by immunocytochemical staining with estrogen receptor-α (ERα)- and estrogen receptor-β (ERβ)-specific antibodies that both ERα and ERβ are expressed in murine NK cells. We also compared the ability of high doses of 17β-estradiol (∼800 pg/ml) to regulate NK cell activity in wild-type and estrogen receptor-α-deficient (ERαKO) mice. 17β-estradiol elicited a significant decrease in NK cell activity in both wild-type and ERαKO mice (P < 0.001). These data suggest that ERβ or possibly a novel receptor is involved in mediating estrogen action on NK cell activity and raise the potential for therapeutic modulation of NK cell activity with selective estrogen receptor modulators (SERMS).

The centromeric part of the human NK gene complex: linkage of LOX-1 and LY49L with the CD94/NKG2 region.

The natural killer (NK) gene complex is a genomic region containing lectin-type receptor genes. We have established a contig of PAC and BAC clones comprising about 1 Mb of the centromeric part of the NK gene complex. This region extends from the LOX-1 gene, which encodes a receptor for oxidized LDL and was found within 100 kb telomeric of the STS marker D12S77, contains the CD94 and NKG2 NK receptor genes and reaches beyond D12S852 on the proximal side. In this part we have mapped the human LY49L gene, a homologue of the rodent Ly49 genes, which encode important MHC class I receptors for the regulation of NK cell activity in rodents. The LY49L gene is localized 100 to 200 kb centromeric of the NKG2 gene cluster and 300 to 400 kb telomeric of the STS marker D12S841. Genomic sequencing of the complete gene including promoter and intron sequences confirmed that the structure is similar to the mouse Ly49 genes. Screening of several cDNA libraries did not detect any transcripts of putative additional human LY49 genes. In addition, in the course of these studies several EST sequences were localized in the region, one immediately upstream of the LY49L gene.

The murine nonclassical class I major histocompatibility complex-like CD1.1 molecule protects target cells from lymphokine-activated killer cell cytolysis.

Classical class I major histocompatibility complex (MHC) molecules, as well as the nonclassical class I histocompatibility leukocyte antigen (HLA)-E molecule, can negatively regulate natural killer (NK) cell cytotoxicity through engagement of NK inhibitory receptors. We show that expression of murine (m)CD1.1, a nonpolymorphic nonclassical MHC class I-like molecule encoded outside the MHC, protects NK-sensitive RMA/S target cells from adherent lymphokine-activated killer cell (A-LAK) cytotoxicity. Passage of effector cells in recombinant interleukin (rIL)-2 enhanced protection by mCD1.1, suggesting an expansion of relevant A-LAK population(s) or modulation of A-LAK receptor expression. Murine CD1. 1 conferred protection from lysis by rIL-2-activated spleen cells of recombination activating gene (Rag)-1(-/-) mice, which lack B and T cells, demonstrating that mCD1.1 can protect RMA/S cells from lysis by NK cells. An antibody specific for mCD1.1 partially restored A-LAK lysis of RMA/S.CD1.1 transfectants, indicating that cell surface mCD1.1 can confer protection from lysis; therefore, mCD1.1 possibly acts through interaction with an NK inhibitory receptor. CD1.1 is by far the most divergent class I molecule capable of regulating NK cell activity. Finally, mCD1.1 expression rendered RMA/S cells resistant to lysis by A-LAK of multiple mouse strains. The conserved structure of mCD1.1 and pattern of mCD1.1 resistance from A-LAK lysis suggest that mCD1.1 may be a ligand for a conserved NK inhibitory receptor.

Regulation of mouse NK cells by structurally divergent inhibitory receptors.

Natural killer (NK) cells contribute to the natural host defense mechanism by lysing certain virally infected and tumor cells and by releasing cytokines that promote an inflammatory immune response. NK cell specificity and the activation events resulting in NK cell stimulation remain poorly understood. However, from parallel studies in rodents and humans it is becoming increasingly evident that a major mode of NK cell specificity is through regulation of NK cell activation by a series of inhibitory receptors specific for MHC class I molecules.KeywordsNatural Killer CellInhibitory ReceptorNatural Killer Cell ReceptorNatural Killer ReceptorMouse Mast CellThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Enhancement of Splenic Interferon-.GAMMA., Interleukin-2, and NK Cytotoxicity by S36 Acupoint Acupuncture in F344 Rats.

The effect of Tsusanli acupuncture point (S36 acupoint) stimulation on splenic natural killer (NK) cytotoxicity was examined in Fischer 344 (F344) rats. Electro-acupuncture stimulation (voltage intensity, 1 to 5 V; duration, 1 ms; frequency, 1 Hz) was applied to bilateral S36 acupoints once a day (1 h) for 3 d. NK cytotoxicity was measured by the standard 4-h 51Cr release assay. Successive acupuncture treatment for 3 d significantly enhanced splenic NK cytotoxicity (p < 0.001) on the first day after final treatment as compared to that of the control. However, similar stimulation to abdominal muscle did not influence splenic NK cytotoxicity. We also examined endogenous cytokine activities in aqueous spleen extracts prepared from acupunctured and control rats. The extracts from rats acupunctured at the S36 acupoint contained high levels of interleukin (IL)-2 and interferon (IFN)-gamma as compared to those of abdominal muscle acupunctured and non-acupunctured control rats (p < 0.01). Furthermore, a significant positive correlation (p < 0.01) was observed between the levels of each cytokine tested and splenic NK cytotoxicity. The same positive correlation was also observed between the levels of IL-2 and IFN-gamma (p < 0.01). These observations indicate that electro-acupuncture stimulation of the S36 acupoint enhances splenic NK cytotoxicity and that IL-2 and IFN-gamma may function, at least in part, in the regulation of NK cell activity in this system.