The targeting vector contains from 5' to 3' a loxP site, cDNA encoding the transmembrane and cytosolic domains of human SIGLEC16 gene, a human growth hormone polyadenylation sequence and an FRT-site flanked neo cassette inserted into exon 4. A second loxP site is inserted downstream of exon 5. Flp-mediated recombination removed the FRT-flanked neo cassette. The human SIGLEC16 activating receptor domain replaces the mouse inhibitory domain encoded by exon 4 of the mouse gene. Expression of human SIGLEC16 is detected in blood neutrophils and macrophages from the liver and spleen of mutant mice. (J:264224)