The transgene comprises a 4.1 kb genomic DNA fragment including the translation initiation codon, all exons and introns, and the polyadenylation signal of the mouse FBJ osteosarcoma [proto-] oncogene joined to a 2 kb fragment containing the promoter and the first nine transcribed base pairs of the mouse H2-Kb gene. All five transgenic lines expressed transgenic mRNA in spleen, thymus, lung and salivary gland, most at high levels; 4/5, at low to moderate levels, in liver and muscle; 3/5 at low levels in heart, gonads and kidney; one, at a low level, in pancreas; and none in brain or bone marrow.