The 20D5 monoclonal antibody reacts with mouse NKG2A, NKG2C, and NKG2E also known as CD159a, CD159c, and CD159e respectively. The NKG2 receptors belong to a family of C-type lectin-like receptors that form heterodimers with CD94. NKG2/CD94 heterodimeric complexes are primarily expressed on NK cells and NKT cells. NKG2 receptors are also expressed on CD8+ T cells activated in vivo and in vitro. NKG2/CD94 heterodimeric complexes recognize Qa-1, a nonclassical MHC class I antigen, presenting the Qdm peptide. CD94/NKG2 heterodimers on NK cells transduce signals after ligand binding. NKG2A is thought to transduce inhibitory signals, while NKG2C and NKG2E transduce stimulatory signals. Blocking NKG2A signaling has been shown to promote anti-tumor immunity in murine tumor models by enhancing the activity of both T and NK cells. For this reason, NKG2A targeting is being explored as a novel immune checkpoint inhibitory therapy for treating human cancers.
*An engineered recombinant mouse variant of the rat IgG2a anti-mouse NKG2A/C/E (clone 20D5) antibody with mouse IgG constant domains has been shown to block NKG2A signals in vivo in murine tumor models. BE0321 is the original 20D5 clone with rat IgG constant domains.
Andre, P., et al. (2018). "Anti-NKG2A mAb Is a Checkpoint Inhibitor that Promotes Anti-tumor Immunity by Unleashing Both T and NK Cells" Cell 175(7): 1731-1743 e1713. PubMed
Checkpoint inhibitors have revolutionized cancer treatment. However, only a minority of patients respond to these immunotherapies. Here, we report that blocking the inhibitory NKG2A receptor enhances tumor immunity by promoting both natural killer (NK) and CD8(+) T cell effector functions in mice and humans. Monalizumab, a humanized anti-NKG2A antibody, enhanced NK cell activity against various tumor cells and rescued CD8(+) T cell function in combination with PD-x axis blockade. Monalizumab also stimulated NK cell activity against antibody-coated target cells. Interim results of a phase II trial of monalizumab plus cetuximab in previously treated squamous cell carcinoma of the head and neck showed a 31% objective response rate. Most common adverse events were fatigue (17%), pyrexia (13%), and headache (10%). NKG2A targeting with monalizumab is thus a novel checkpoint inhibitory mechanism promoting anti-tumor immunity by enhancing the activity of both T and NK cells, which may complement first-generation immunotherapies against cancer.
in vivo NKG2A blockade
van Montfoort, N., et al. (2018). "NKG2A Blockade Potentiates CD8 T Cell Immunity Induced by Cancer Vaccines" Cell 175(7): 1744-1755 e1715. PubMed
Tumor-infiltrating CD8 T cells were found to frequently express the inhibitory receptor NKG2A, particularly in immune-reactive environments and after therapeutic cancer vaccination. High-dimensional cluster analysis demonstrated that NKG2A marks a unique immune effector subset preferentially co-expressing the tissue-resident CD103 molecule, but not immune checkpoint inhibitors. To examine whether NKG2A represented an adaptive resistance mechanism to cancer vaccination, we blocked the receptor with an antibody and knocked out its ligand Qa-1(b), the conserved ortholog of HLA-E, in four mouse tumor models. The impact of therapeutic vaccines was greatly potentiated by disruption of the NKG2A/Qa-1(b) axis even in a PD-1 refractory mouse model. NKG2A blockade therapy operated through CD8 T cells, but not NK cells. These findings indicate that NKG2A-blocking antibodies might improve clinical responses to therapeutic cancer vaccines.
Immunohistochemistry (frozen), Flow Cytometry
Yang, R. K., et al. (2012). "Intratumoral hu14.18-IL-2 (IC) induces local and systemic antitumor effects that involve both activated T and NK cells as well as enhanced IC retention" J Immunol 189(5): 2656-2664. PubMed
hu14.18-IL-2 (IC) is an immunocytokine consisting of human IL-2 linked to hu14.18 mAb, which recognizes the GD2 disialoganglioside. Phase 2 clinical trials of i.v. hu14.18-IL-2 (i.v.-IC) in neuroblastoma and melanoma are underway and have already demonstrated activity in neuroblastoma. We showed previously that intratumoral hu14.18-IL-2 (IT-IC) results in enhanced antitumor activity in mouse models compared with i.v.-IC. The studies presented in this article were designed to determine the mechanisms involved in this enhanced activity and to support the future clinical testing of intratumoral administration of immunocytokines. Improved survival and inhibition of growth of both local and distant tumors were observed in A/J mice bearing s.c. NXS2 neuroblastomas treated with IT-IC compared with those treated with i.v.-IC or control mice. The local and systemic antitumor effects of IT-IC were inhibited by depletion of NK cells or T cells. IT-IC resulted in increased NKG2D receptors on intratumoral NKG2A/C/E(+) NKp46(+) NK cells and NKG2A/C/E(+) CD8(+) T cells compared with control mice or mice treated with i.v.-IC. NKG2D levels were augmented more in tumor-infiltrating lymphocytes compared with splenocytes, supporting the localized nature of the intratumoral changes induced by IT-IC treatment. Prolonged retention of IC at the tumor site was seen with IT-IC compared with i.v.-IC. Overall, IT-IC resulted in increased numbers of activated T and NK cells within tumors, better IC retention in the tumor, enhanced inhibition of tumor growth, and improved survival compared with i.v.-IC.
in vitro NKG2A blockade, Flow Cytometry
Vance, R. E., et al. (1999). "Recognition of the class Ib molecule Qa-1(b) by putative activating receptors CD94/NKG2C and CD94/NKG2E on mouse natural killer cells" J Exp Med 190(12): 1801-1812. PubMed
The heterodimeric CD94/NKG2A receptor, expressed by mouse natural killer (NK) cells, transduces inhibitory signals upon recognition of its ligand, Qa-1(b), a nonclassical major histocompatibility complex class Ib molecule. Here we clone and express two additional receptors, CD94/NKG2C and CD94/NKG2E, which we show also bind to Qa-1(b). Within their extracellular carbohydrate recognition domains, NKG2C and NKG2E share extensive homology with NKG2A (93-95% amino acid similarity); however, NKG2C/E receptors differ from NKG2A in their cytoplasmic domains (only 33% similarity) and contain features that suggest that CD94/NKG2C and CD94/NKG2E may be activating receptors. We employ a novel blocking anti-NKG2 monoclonal antibody to provide the first direct evidence that CD94/NKG2 molecules are the only Qa-1(b) receptors on NK cells. Molecular analysis reveals that NKG2C and NKG2E messages are extensively alternatively spliced and approximately 20-fold less abundant than NKG2A message in NK cells. The organization of the mouse Cd94/Nkg2 gene cluster, presented here, shows striking similarity with that of the human, arguing that the entire CD94/NKG2 receptor system is relatively primitive in origin. Analysis of synonymous substitution frequencies suggests that within a species, NKG2 genes may maintain similarities with each other by concerted evolution, possibly involving gene conversion-like events. These findings have implications for understanding NK cells and also raise new possibilities for the role of Qa-1 in immune responses.
