Dr. George Snell, of The Jackson Laboratory, created this H2-congenic strain by crossing of mice of a non-inbred stock carrying the brachyury mutation (and therefore called BY) to mice of the A/Lilly inbred strain, then repeatedly backcrossing to the latter strain mice that proved resistant to A-derived tumors. A/Lilly was a subline of strain A that Snell obtained from the Lilly Company after the 1947 fire at The Jackson Laboratory; when it was learned that this strain was contaminated, Snell performed a single additional backcross to the A/WySn subline, taking it to generation N11 (Rodgers 2004; Klein 1989). The BY stock apparently was obtained from Dr. Dobrovolskaia-Zavadskaia, who described a short-tailed mouse sired by a gonadally-irradiated male; she believed the brachyury mutation not to have been caused by the radiation, but to have been a pre-existing spontaneous mutation (Dobrovoskaya-Zajadkaya 1927; Rodgers 2004). In a subsequent article, she described short tailed (brachyure) and tailless (anoure) mice - the latter presumaby T/t - from the same litters, but these may have come from a different investigator (Rodgers 2004).

The H2-T18 locus, which previously was called Tla and whose encoded proteins have been referred to as TL antigens, was discovered by Dr. Lloyd Old and colleagues when antisera produced by C57BL/6 mice following immunization with leukemia cells from A strain mice were found to react with thymocytes from a subset of mouse strains, as well as with cells of particular leukemias. Interestingly, some leukemias expressed the reactive antigen despite being from mice of strains whose thymocytes were negative for the antigen. Different antigens and combinations of antigens were identified in thymocytes of various mouse strains using a series of antisera. By such serological analysis, thymocytes from mice of all H2^b strains were negative for any TL antigen. (For a review of the Tla genes and their encoded antigens and additional references, see Chorney et al. 1982.)

This strain, like C57L, LP/J and 129 substrains, was classified in early articles dealing with H2-T18/Tla/TL as having the null, H2-T18^b haplotype of other H2^b strains. Shen et al. (1982), using a panel of monoclonal antibodies, identified a new Tla specificity, which they assigned the f haplotype, shared by this subset of otherwise H2^b strains. Snell realized earlier from results of transplantation studies that A.BY differed from other H2^b strains and that the difference mapped to the region of Tla; he therefore proposed to call the H2 haplotype of A.BY bc, as this was the next H2^b variant in the series. We therefore have renamed this strain accordingly.