Specific antibody binding to CD161 but not other C-type lectins with significant sequence homology. Jurkat cells were lentivirally transduced with complementary DNAs (cDNAs) encoding human (Homo sapiens) or nonhuman primate (Macaca fascicularis) CD161 (KLRB1 gene) or other human C-type lectins with significant sequence homology to CD161. (A) Assay for assessing CLEC2D-Ig binding to CD161 and other C-type lectins. (B) Analysis of bivalent CLEC2D-Ig binding to the indicated panel of transfectants. Each cell line was incubated with CLEC2D-Ig, and binding was detected with anti-Fc/APC–conjugated antibody. Percent of sequence identity to the extracellular domain of human CD161 is indicated for each homolog. (C) Quantification of mean fluorescence intensity of CLEC2D-Ig bound to the panel of transfectants (combined data for 2 independent assays). (D) CD161 antibody binding to CD161 or other C-type lectin receptors. Each cell line was incubated with CD161 mAb KW7.3.7, and binding was detected with anti-Fc/APC–conjugated antibody. (E) Binding of human bivalent CLEC2D-Ig to murine C57BL/6 NK cells (NK1.1⁺ CD49b⁺ CD3^– [left]) and T cells (CD3⁺ NK1.1^– [right]). (F) CD161 antibody binding to murine C57BL/6 NK cells (left) and T cells (right). Representative results from at least 2 independent experiments (B-F). Unpaired t test: ∗∗∗P < .001. APC, antigen presenting cells.