Targeting of the CD161 Inhibitory Receptor Enhances T-cell-mediated Immunity Against Hematological Malignancies.

The CD161 inhibitory receptor is highly upregulated by tumor -in fi ltrating T cells in multiple human solid tumor types, and its ligand, CLEC2D, is expressed by both tumor cells and in fi ltrating myeloid cells. Here, we assessed the role of the CD161 receptor in hematological malignancies. Systematic analysis of CLEC2D expression using the Cancer Cell Line Encyclopedia revealed that CLEC2D messenger RNA was most abundant in hematological malignancies, including B -cell and T -cell lymphomas as well as lymphocytic and myelogenous leukemias. CLEC2D protein was detected by fl ow cytometry on a panel of cell lines representing a diverse set of hematological malignancies. We, therefore, used yeast display to generate a panel of high -affinity, fully human CD161 monoclonal antibodies (mAbs) that blocked CLEC2D binding. These mAbs were speci fi c for CD161 and had a similar af fi nity for human and nonhuman primate CD161, a property relevant for clinical translation. A high -affinity CD161 mAb enhanced key aspects of T -cell function, including cytotoxicity, cytokine production, and proliferation, against B -cell lines originating from patients with acute lymphoblastic leukemia, diffuse large B -cell lymphoma, and Burkitt lymphoma. In humanized mouse models, this CD161 mAb enhanced T-cell-mediated immunity, resulting in a signi fi cant survival bene fi t. Single cell RNA-seq data demonstrated that CD161 mAb treatment enhanced expression of cytotoxicity genes by CD4 T cells as well as a tissue -residency program by CD4 and CD8 T cells that is associated with favorable survival outcomes in multiple human cancer types. These fully human mAbs, thus, represent potential immunotherapy agents for hematological malignancies.