Receptor for CLEC2D/OCIL. Ligand-binding contributes to inhibition of cytotoxic natural killer (NK) cells. May mediate MHC class I-independent 'missing-self' recognition of allografts, tumor cells and virus-infected cells. Homodimer; disulfide-linked. Interacts with tyrosine kinase LCK. Binds PTPN6/SHP-1 in a phosphorylation-dependent manner. Expressed in NK cells and a subset of T-cells. Contains 1 copy of a cytoplasmic motif that is referred to as the immunoreceptor tyrosine-based inhibitor motif (ITIM). The phosphorylated ITIM motif can bind the SH2 domain of several SH2-containing phosphatases leading to down-regulation of cell activation. Variants Thr-191 and Ala-191 interfere with binding of the anti-NK1.1 monoclonal antibody PK136 which identifies NK cells from C57BL/6 and SJL but not BALB/c mice by binding Klrb1b and Klrb1c in an allele-dependent manner. Mutagenesis of Thr-191 to Ser-191 restores NK1.1 reactivity to Klrb1b from BALB/c mice.