The isoforms of rat natural killer cell receptor NKR-P1 display a distinct binding of complex saccharide ligands

Lectin-like receptors of natural killer cells are critical for the regulation of their effector function. When these receptors are crosslinked with antibodies or multivalent ligands, they transmit either activating or inhibitory signals. Here we describe binding and inhibition experiments with recombinant extracellular ligand-binding domains of the rat NKR-P1A ( activating) and NKR-P1B ( inhibitory) receptors. We did not observe any difference in the binding of monosaccharide ligands by these receptors, but revealed dramatic differences in the binding of oligosaccharides and glycodendrimers. Our results explain the immunostimulatory effects of the glycodendrimers, which bind exclusively to the activating NKR-P1A isoform.