Sequence encoding conserved amino acids 75 through 86 (YSDLNTQRQYR) of the immunoreceptor tyrosine-based activation motif (ITAM) was replaced with a vector containing a floxed neo cassette followed by sequence encoding a putatively non-functional 15 amino acid peptide (GLQEFIEDEKKKRNSI). Mice carrying this allele were bred with transgenic mice expressing cre via the ubiquitous CMV promoter to generate Tyrobptm1.1Viv. (J:64764)