scholarly journals Centromeric KIR AA Individuals Harbor Particular KIR Alleles Conferring Beneficial NK Cell Features with Implications in Haplo-Identical Hematopoietic Stem Cell Transplantation

Cancers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3595
Author(s):  
Léa Dubreuil ◽  
Bercelin Maniangou ◽  
Patrice Chevallier ◽  
Agnès Quéméner ◽  
Nolwenn Legrand ◽  
...  
Keyword(s):  
Nk Cells ◽  
Nk Cell ◽  
Killer Cell ◽  
Allelic Polymorphism ◽  
Functional Effect ◽  
Cell Frequency ◽  
Hematopoietic Stem ◽  
Cell Responses ◽  
Allele Expression

We have recently shown a broad disparity of Natural Killer (NK) cell responses against leukemia highlighting good and bad responders resting on the Killer cell Immunoglobulin-like Receptors (KIR) and HLA genetics. In this study, we deeply studied KIR2D allele expression, HLA-C recognition and functional effect on NK cells in 108 blood donors in combining high-resolution KIR allele typing and multicolor flow cytometry. The KIR2DL1*003 allotype is associated with centromeric (cen) AA motif and confers the highest NK cell frequency, expression level and strength of KIR/HLA-C interactions compared to the KIR2DL1*002 and KIR2DL1*004 allotypes respectively associated with cenAB and BB motifs. KIR2DL2*001 and *003 allotypes negatively affect the frequency of KIR2DL1+ and KIR2DL3+ NK cells. Altogether, our data suggest that cenAA individuals display more efficient KIR2DL alleles (L1*003 and L3*001) to mount a consistent frequency of KIR2DL+ NK cells and to confer an effective NK cell responsiveness. The transposition of our in vitro observations in the T-replete haplo-identical HSCT context led us to observe that cenAA HSC grafts limit significantly the incidence of relapse in patients with myeloid diseases after T-replete haplo-identical HSCT. As NK cells are crucial in HSCT reconstitution, one could expect that the consideration of KIR2DL1/2/3 allelic polymorphism could help to refine scores used for HSC donor selection.

scholarly journals Potently Cytotoxic Natural Killer Cell Potential Initially Emerges from Erythro-Myeloid Progenitors during Mammalian Development

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2464-2464
Author(s):  
Carissa Dege ◽  
Katherine H Fegan ◽  
J Philip Creamer ◽  
Melissa M Berrien-Elliott ◽  
Stephanie A. Luff ◽  
...  
Keyword(s):  
Nk Cells ◽  
Natural Killer ◽  
Nk Cell ◽  
Fetal Liver ◽  
Killer Cell ◽  
Hematopoietic Progenitors ◽  
Cell Potential ◽  
Hematopoietic Stem ◽  
Myeloid Progenitor

Natural killer (NK) cells are innate immune cells that target and kill virally infected and malignant cells, making them an attractive target for adoptive immunotherapies. An alternative to donor-derived NK cells is the use of human pluripotent stem cell (hPSC)-derived NK cells, as a renewable "off the shelf" product. Previous studies have identified hPSC-derived NK cells as potently cytotoxic, compared to donor-derived NK cells. As the differentiation of hPSCs mimics early embryonic development, this raises the possibility that hPSC-derived NK cells are ontogenically distinct from adult NK cells. NK cells are present during embryonic hematopoiesis, but their ontogenic origins are poorly understood. NK cells are thought to arise from a common lymphoid progenitor (CLP), lying downstream of hematopoietic stem cells (HSCs), but evidence exists that NK cells may arise from HSC-independent progenitors as NK cells are found in the early murine fetal liver, and NK cell progenitors are found in the early human yolk sac (YS). In this study, we investigated the emergence of NK cells during murine and human embryonic hematopoietic development. During murine embryogenesis, overlapping HSC-independent waves of hematopoietic progenitors occur in the YS that give rise to hematopoietic cells prior to HSC emergence at E10.5. The "primitive" wave occurs at E7.5, followed by an "erythro-myeloid progenitor" (EMP) wave at E8.5. To study NK cell potential during murine YS hematopoiesis, we cultured total YS and sorted hematopoietic progenitors under NK cell promoting conditions. Strikingly, we found that the YS contains NK cell potential. Further, sorted E8.5 kit+CD41+CD16/32+ EMP progenitors, but not primitive hematopoietic progenitors, contain robust NK cell potential. EMP-derived NK (EMP-NK) cells were larger and more granular than adult CLP-derived NK cells. Additionally, NK cells from the E15.5 fetal liver were larger and more granular than NK cells from the adult spleen. Both EMP-NK cells and E15.5 fetal liver NK cells had a more robust degranulation response than their HSC-derived counterparts. Together, these data support the concept that EMP in the YS serve as an initial source of physiologically relevant, functional embryonic NK cells that are phenotypically and functionally distinct from adult NK cells. As hPSC-derived NK cells were described as potently cytotoxic, and we observed that murine HSC-independent NK cells robustly degranulate, we next asked whether NK cell development from hPSCs recapitulates that found in the murine embryo. We have demonstrated previously, using a stage-specific WNT signal manipulation approach that specifies ontogenically distinct hematopoietic progenitors, that hPSC-derived NK cell progenitors can be obtained from two distinct progenitors in vitro. In this study, we sought to better understand the development and function of these two NK cell populations. Stage-specific WNT inhibition (WNTi) during hPSC mesodermal patterning yielded extra-embryonic-like HOXA-/low CD34+ populations that possessed erythroid, myeloid and NK cell potential, but lacked T cell potential. The CD56+ NK cells in these cultures co-emerged with CD15+ granulocytes, indicating that these NK cells may arise from a committed myeloid progenitor. In contrast, HOXA+ CD34+ cells, obtained in a WNT-dependent (WNTd) manner, harbored erythro-myelo-lymphoid multi-lineage potential, including NK cell potential. Phenotypically, WNTi-NK cells were larger, more granular and more mature, compared to WNTd-NK and cord blood (CB)-derived NK cells, reminiscent of murine EMP-NK cells. Further, following multiple stimulation assays, WNTi-NK and WNTd-NK cells had different effector biases. WNTi-NK cells are biased for potent cytotoxic degranulation and exhibited superior cell killing in an ADCC assay. In contrast, WNTd-NK and CB-NK had an attenuated degranulation response, but robustly produced inflammatory cytokines. Finally, RNA-seq analysis demonstrated that WNTd-NK cells were most similar to CB-NK cells. Collectively, these studies identify for the first time that the murine EMP harbor NK cell potential, and these NK cells are functionally unique. These observations raise new questions regarding which ontogenic origin of NK cells should be used in future hPSC-derived adoptive immunotherapy strategies. Disclosures Fehniger: Cyto-Sen Therapeutics: Consultancy; Horizon Pharma PLC: Other: Consultancy (Spouse). Palis:Rubius Therapeutics: Consultancy.

scholarly journals Genetic and Molecular Basis of Heterogeneous NK Cell Responses against Acute Leukemia

Cancers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1927 ◽  
Author(s):  
Dhon Roméo Makanga ◽  
Francesca Da Rin de Lorenzo ◽  
Gaëlle David ◽  
Catherine Willem ◽  
Léa Dubreuil ◽  
...  
Keyword(s):  
Nk Cells ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Lymphoblastic Leukemia ◽  
Killer Cell ◽  
Cell Repertoire ◽  
Hematopoietic Stem ◽  
Cell Responses ◽  
Cmv Status ◽  
Selection Of

Natural killer (NK) cells are key cytotoxic effectors against malignant cells. Polygenic and polymorphic Killer cell Immunoglobulin-like Receptor (KIR) and HLA genes participate in the structural and functional formation of the NK cell repertoire. In this study, we extensively investigated the anti-leukemic potential of NK cell subsets, taking into account these genetic parameters and cytomegalovirus (CMV) status. Hierarchical clustering analysis of NK cell subsets based on NKG2A, KIR, CD57 and NKG2C markers from 68 blood donors identified donor clusters characterized by a specific phenotypic NK cell repertoire linked to a particular immunogenetic KIR and HLA profile and CMV status. On the functional side, acute lymphoblastic leukemia (ALL) was better recognized by NK cells than acute myeloid leukemia (AML). However, a broad inter-individual disparity of NK cell responses exists against the same leukemic target, highlighting bad and good NK responders. The most effective NK cell subsets against different ALLs expressed NKG2A and represented the most frequent subset in the NK cell repertoire. In contrast, minority CD57+ or/and KIR+ NK cell subsets were more efficient against AML. Overall, our data may help to optimize the selection of hematopoietic stem cell donors on the basis of immunogenetic KIR/HLA for ALL patients and identify the best NK cell candidates in immunotherapy for AML.

scholarly journals The m15 Locus of Murine Cytomegalovirus Modulates Natural Killer Cell Responses to Promote Dissemination to the Salivary Glands and Viral Shedding

Pathogens ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 866
Author(s):  
Baca Chan ◽  
Maja Arapović ◽  
Laura Masters ◽  
Francois Rwandamuiye ◽  
Stipan Jonjić ◽  
...  
Keyword(s):  
Nk Cells ◽  
Salivary Glands ◽  
Natural Killer ◽  
Nk Cell ◽  
Acute Infection ◽  
Killer Cell ◽  
Viral Escape ◽  
Murine Cytomegalovirus ◽  
Viral Shedding ◽  
Cell Responses

As the largest herpesviruses, the 230 kb genomes of cytomegaloviruses (CMVs) have increased our understanding of host immunity and viral escape mechanisms, although many of the annotated genes remain as yet uncharacterised. Here we identify the m15 locus of murine CMV (MCMV) as a viral modulator of natural killer (NK) cell immunity. We show that, rather than discrete transcripts from the m14, m15 and m16 genes as annotated, there are five 3′-coterminal transcripts expressed over this region, all utilising a consensus polyA tail at the end of the m16 gene. Functional inactivation of any one of these genes had no measurable impact on viral replication. However, disruption of all five transcripts led to significantly attenuated dissemination to, and replication in, the salivary glands of multiple strains of mice, but normal growth during acute infection. Disruption of the m15 locus was associated with heightened NK cell responses, including enhanced proliferation and IFNγ production. Depletion of NK cells, but not T cells, rescued salivary gland replication and viral shedding. These data demonstrate the identification of multiple transcripts expressed by a single locus which modulate, perhaps in a concerted fashion, the function of anti-viral NK cells.

scholarly journals Cytokine-Induced Memory-Like NK Cells with High Reactivity against Acute Leukemia Blasts and Solid Tumor Cells Suitable for Adoptive Immunotherapy Approaches

Cancers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1577
Author(s):  
Matteo Tanzi ◽  
Michela Consonni ◽  
Michela Falco ◽  
Federica Ferulli ◽  
Enrica Montini ◽  
...  
Keyword(s):  
Acute Leukemia ◽  
Nk Cells ◽  
Tumor Cells ◽  
Cell Function ◽  
Nk Cell ◽  
Autologous Tumor ◽  
Lymphoid Leukemia ◽  
Hematopoietic Stem ◽  
Solid Malignancies

The limited efficacy of Natural Killer (NK) cell-based immunotherapy results in part from the suboptimal expansion and persistence of the infused cells. Recent reports suggest that the generation of NK cells with memory-like properties upon in vitro activation with defined cytokines might be an effective way of ensuring long-lasting NK cell function in vivo. Here, we demonstrate that activation with IL-12, IL-15 and IL-18 followed by a one-week culture with optimal doses of Interleukin (IL-2) and IL-15 generates substantial numbers of memory-like NK cells able to persist for at least three weeks when injected into NOD scid gamma (NSG) mice. This approach induces haploidentical donor-derived memory-like NK cells that are highly lytic against patients’ myeloid or lymphoid leukemia blasts, independent of the presence of alloreactive cell populations in the donor and with negligible reactivity against patients’ non-malignant cells. Memory-like NK cells able to lyse autologous tumor cells can also be generated from patients with solid malignancies. The anti-tumor activity of allogenic and autologous memory-like NK cells is significantly greater than that displayed by NK cells stimulated overnight with IL-2, supporting their potential therapeutic value both in patients affected by high-risk acute leukemia after haploidentical hematopoietic stem cell transplantation and in patients with advanced solid malignancies.

scholarly journals Combining Immunocytokine and Ex Vivo Activated NK Cells as a Platform for Enhancing Graft-Versus-Tumor Effects Against GD2+ Murine Neuroblastoma

2021 ◽  
Vol 12 ◽  
Author(s):  
Paul D. Bates ◽  
Alexander L. Rakhmilevich ◽  
Monica M. Cho ◽  
Myriam N. Bouchlaka ◽  
Seema L. Rao ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Nk Cells ◽  
Nk Cell ◽  
Ex Vivo ◽  
Cell Transplant ◽  
Hematopoietic Stem ◽  
Allogeneic Hsct ◽  
Tnf Α

Management for high-risk neuroblastoma (NBL) has included autologous hematopoietic stem cell transplant (HSCT) and anti-GD2 immunotherapy, but survival remains around 50%. The aim of this study was to determine if allogeneic HSCT could serve as a platform for inducing a graft-versus-tumor (GVT) effect against NBL with combination immunocytokine and NK cells in a murine model. Lethally irradiated C57BL/6 (B6) x A/J recipients were transplanted with B6 bone marrow on Day +0. On day +10, allogeneic HSCT recipients were challenged with NXS2, a GD2+ NBL. On days +14-16, mice were treated with the anti-GD2 immunocytokine hu14.18-IL2. In select groups, hu14.18-IL2 was combined with infusions of B6 NK cells activated with IL-15/IL-15Rα and CD137L ex vivo. Allogeneic HSCT alone was insufficient to control NXS2 tumor growth, but the addition of hu14.18-IL2 controlled tumor growth and improved survival. Adoptive transfer of ex vivo CD137L/IL-15/IL-15Rα activated NK cells with or without hu14.18-IL2 exacerbated lethality. CD137L/IL-15/IL-15Rα activated NK cells showed enhanced cytotoxicity and produced high levels of TNF-α in vitro, but induced cytokine release syndrome (CRS) in vivo. Infusing Perforin-/- CD137L/IL-15/IL-15Rα activated NK cells had no impact on GVT, whereas TNF-α-/- CD137L/IL-15/IL-15Rα activated NK cells improved GVT by decreasing peripheral effector cell subsets while preserving tumor-infiltrating lymphocytes. Depletion of Ly49H+ NK cells also improved GVT. Using allogeneic HSCT for NBL is a viable platform for immunocytokines and ex vivo activated NK cell infusions, but must be balanced with induction of CRS. Regulation of TNFα or activating NK subsets may be needed to improve GVT effects.

scholarly journals RTID-07. HUMAN PLACENTAL HEMATOPOIETIC STEM CELL DERIVED NATURAL KILLER CELLS (CYNK-001) FOR TREATMENT OF RECURRENT GLIOBLASTOMA

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii194-ii195
Author(s):  
Nazanin Majd ◽  
Maha Rizk ◽  
Solveig Ericson ◽  
Kris Grzegorzewski ◽  
Sharmila Koppisetti ◽  
...  
Keyword(s):  
Cell Therapy ◽  
Nk Cells ◽  
Natural Killer ◽  
Nk Cell ◽  
In Vitro Cytotoxicity ◽  
Orthotopic Mouse Model ◽  
Hematopoietic Stem ◽  
Dismal Prognosis

Abstract Glioblastoma (GBM) is the most aggressive primary brain tumor with dismal prognosis. Recent advances of immunotherapy in cancer have sparked interest in the use of cell therapy for treatment of GBM. Active transfer of Natural Killer (NK) cells is of particular interest in GBM because NK cells are capable of exerting anti-tumor cytotoxicity without the need for antigen presentation and sensitization, processes that are impaired in GBM. CYNK-001 is an allogeneic, off-the-shelf product enriched for CD56+/CD3- NK cells expanded from placental CD34+ cells manufactured by Celularity. Here, we demonstrate in vitro cytotoxicity of CYNK-001 against several GBM lines and its in vivo anti-tumor activity in a U87MG orthotopic mouse model via intracranial administration resulting in 94.5% maximum reduction in tumor volume. We have developed a phase I window-of-opportunity trial of CYNK-001 in recurrent GBM via intravenous (IV) and intratumoral (IT) routes. In the IV cohort, subjects receive cyclophosphamide for lymphodepletion followed by 3-doses of IV CYNK-001 weekly. In the IT cohort, subjects undergo placement of an IT catheter with an ommaya reservoir followed by 3-doses of IT CYNK-001 weekly. Patients are monitored for 28-days after last infusion for toxicity. Once maximum safe dose (MSD) is determined, patients undergo IV or IT treatments at MSD followed by surgical resection and the tumor tissue will be analyzed for NK cell engraftment and persistence. We will utilize a 3 + 3 dose de-escalation design (maximum n=36). Primary endpoint is safety and feasibility. Secondary endpoints are overall response rate, duration of response, time to progression, progression free survival and overall survival. Main eligibility criteria include age ≥18, KPS ≥60, GBM at first or second relapse with a measurable lesion on ≤2mg dexamethasone. This is the first clinical trial to investigate CYNK-001 in GBM and will lay the foundation for future NK cell therapy in solid tumors.

scholarly journals An Anti-MICA/B Antibody and IL-15 Rescue Altered NKG2D-Dependent NK Cell Responses in Hepatocellular Carcinoma

Cancers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3583
Author(s):  
Stefania Mantovani ◽  
Stefania Varchetta ◽  
Dalila Mele ◽  
Matteo Donadon ◽  
Guido Torzilli ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Nk Cells ◽  
Natural Killer ◽  
Nk Cell ◽  
Protein A ◽  
Ligand Interaction ◽  
Cell Responses ◽  
Hcc Cells

Natural killer (NK) cells play a pivotal role in cancer immune surveillance, and activating the receptor/ligand interaction may contribute to control the development and evolution of hepatocellular carcinoma (HCC). We investigated the role of the natural killer group 2 member D (NKG2D) activating receptor and its ligand, the major histocompatibility complex class I chain-related protein A and B (MICA/B) in patients with cirrhosis and HCC subjected to surgical resection, patients with cirrhosis and no HCC, and healthy donors (HD). The NKG2D-mediated function was determined in peripheral blood (PB), in tumor-infiltrating lymphocytes (NK-TIL), and in matched surrounding liver tissue (NK-LIL). A group of patients treated with sorafenib because of clinically advanced HCC was also studied. A humanized anti-MICA/B monoclonal antibody (mAb) was used in in vitro experiments to examine NK cell-mediated antibody-dependent cellular cytotoxicity. Serum concentrations of soluble MICA/B were evaluated by ELISA. IL-15 stimulation increased NKG2D-dependent activity which, however, remained dysfunctional in PB NK cells from HCC patients, in line with the reduced NKG2D expression on NK cells. NK-TIL showed a lower degranulation ability than NK-LIL, which was restored by IL-15 stimulation. Moreover, in vitro IL-15 stimulation enhanced degranulation and interferon-γ production by PB NK from patients at month one of treatment with sorafenib. Anti-MICA/B mAb associated with IL-15 was able to induce PB NK cytotoxicity for primary HCC cells in HD and patients with HCC, who also showed NK-TIL degranulation for autologous primary HCC cells. Our findings highlight the key role of the NKG2D-MICA/B axis in the regulation of NK cell responses in HCC and provide evidence in support of a potentially important role of anti-MICA/B mAb and IL-15 stimulation in HCC immunotherapy.

scholarly journals SARS-CoV-2 Spike 1 Protein Controls Natural Killer Cell Activation via the HLA-E/NKG2A Pathway

Cells ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1975 ◽  
Author(s):  
Daria Bortolotti ◽  
Valentina Gentili ◽  
Sabrina Rizzo ◽  
Antonella Rotola ◽  
Roberta Rizzo
Keyword(s):  
Epithelial Cells ◽  
Nk Cells ◽  
Natural Killer ◽  
Cell Activation ◽  
Nk Cell ◽  
Killer Cell ◽  
Lung Epithelial Cells ◽  
Lung Epithelial ◽  
Spike Proteins

Natural killer cells are important in the control of viral infections. However, the role of NK cells during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has previously not been identified. Peripheral blood NK cells from SARS-CoV and SARS-CoV-2 naïve subjects were evaluated for their activation, degranulation, and interferon-gamma expression in the presence of SARS-CoV and SARS-CoV-2 spike proteins. K562 and lung epithelial cells were transfected with spike proteins and co-cultured with NK cells. The analysis was performed by flow cytometry and immune fluorescence. SARS-CoV and SARS-CoV-2 spike proteins did not alter NK cell activation in a K562 in vitro model. On the contrary, SARS-CoV-2 spike 1 protein (SP1) intracellular expression by lung epithelial cells resulted in NK cell-reduced degranulation. Further experiments revealed a concomitant induction of HLA-E expression on the surface of lung epithelial cells and the recognition of an SP1-derived HLA-E-binding peptide. Simultaneously, there was increased modulation of the inhibitory receptor NKG2A/CD94 on NK cells when SP1 was expressed in lung epithelial cells. We ruled out the GATA3 transcription factor as being responsible for HLA-E increased levels and HLA-E/NKG2A interaction as implicated in NK cell exhaustion. We show for the first time that NK cells are affected by SP1 expression in lung epithelial cells via HLA-E/NKG2A interaction. The resulting NK cells’ exhaustion might contribute to immunopathogenesis in SARS-CoV-2 infection.

Expression patterns of NKG2A, KIR, and CD57 define a process of CD56dim NK-cell differentiation uncoupled from NK-cell education

Blood ◽  
2010 ◽  
Vol 116 (19) ◽  
pp. 3853-3864 ◽  
Author(s):  
Niklas K. Björkström ◽  
Peggy Riese ◽  
Frank Heuts ◽  
Sandra Andersson ◽  
Cyril Fauriat ◽  
...  
Keyword(s):  
Immune System ◽  
Cell Differentiation ◽  
Nk Cells ◽  
Nk Cell ◽  
Expression Patterns ◽  
Killer Cell ◽  
Human Leukocyte ◽  
Phenotypic Properties ◽  
Hematopoietic Stem ◽  
Nk Cell Differentiation

Abstract Natural killer (NK) cells are lymphocytes of the innate immune system that, following differentiation from CD56bright to CD56dim cells, have been thought to retain fixed functional and phenotypic properties throughout their lifespan. In contrast to this notion, we here show that CD56dim NK cells continue to differentiate. During this process, they lose expression of NKG2A, sequentially acquire inhibitory killer cell inhibitory immunoglobulin-like receptors and CD57, change their expression patterns of homing molecules, and display a gradual decline in proliferative capacity. All cellular intermediates of this process are represented in varying proportions at steady state and appear, over time, during the reconstitution of the immune system, as demonstrated in humanized mice and in patients undergoing hematopoietic stem cell transplantation. CD56dim NK-cell differentiation, and the associated functional imprint, occurs independently of NK-cell education by interactions with self–human leukocyte antigen class I ligands and is an essential part of the formation of human NK-cell repertoires.

scholarly journals Natural killer cells suppress human erythroid stem cell proliferation in vitro

Blood ◽  
1984 ◽  
Vol 63 (2) ◽  
pp. 260-269 ◽  
Author(s):  
KF Mangan ◽  
ME Hartnett ◽  
SA Matis ◽  
A Winkelstein ◽  
T Abo
Keyword(s):  
Stem Cell ◽  
Natural Killer Cell ◽  
Nk Cells ◽  
Natural Killer ◽  
Nk Cell ◽  
Killer Cell ◽  
Human Natural Killer Cell ◽  
Percoll Density Gradient Centrifugation

Abstract To determine the role of natural killer (NK) cells in the regulation of human erythropoiesis, we studied the effects of NK-enriched cell populations on the in vitro proliferation of erythroid stem cells at three different levels of maturation (day 14 blood BFU-E, day 5–6 marrow CFU-E, and day 10–12 marrow BFU-E). NK cells were enriched from blood by Percoll density gradient centrifugation and by fluorescence- activated cell sorting (FACS), using the human natural killer cell monoclonal antibody, HNK-1. The isolated enriched fractions were cocultured with autologous nonadherent marrow cells or blood null cells and erythropoietin in a methylcellulose erythroid culture system. Cells from low-density Percoll fractions (NK-enriched cells) were predominantly large granular lymphocytes with cytotoxic activity against K562 targets 6–10-fold greater than cells obtained from high- density Percoll fractions (NK-depleted cells). In coculture with marrow nonadherent cells (NA) at NK:NA ratios of 2:1, NK-enriched cells suppressed day 5–6 CFU-E to 62% (p less than 0.025) of controls, whereas NK-depleted cells slightly augmented CFU-E to 130% of controls (p greater than 0.05). In contrast, no suppression of day 10–12 marrow BFU-E was observed employing NK-enriched cells. The NK CFU-E suppressor effects were abolished by complement-mediated lysis of NK-enriched cells with the natural killer cell antibody, HNK-1. Highly purified HNK- 1+ cells separated by FACS suppressed marrow CFU-E to 34% (p less than 0.025) and marrow BFU-E to 41% (p less than 0.025) of controls. HNK- cells had no significant effect on either BFU-E or CFU-E growth. NK- enriched cells were poor stimulators of day 14 blood BFU-E in comparison to equal numbers of NK-depleted cells or T cells isolated by E-rosetting (p less than 0.01). Interferon boosting of NK-enriched cells abolished their suboptimal burst-promoting effects and augmented their CFU-E suppressor effects. These studies provide evidence for a potential regulatory role of NK cells in erythropoiesis. The NK suppressor effect is maximal at the level of the mature erythroid stem cell CFU-E. These findings may explain some hypoproliferative anemias that develop in certain NK cell-activated states.

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