Identification of a recombinational breakpoint at the BAT5 locus in three intra-H-2 recombinant inbred mouse strains.

We have analyzed the S/D region in 14 inbred mouse strains by restriction fragment length polymorphism (RFLP) using human BAT2 and BAT5 genes as probes. In all recombinant strains, the recombinational breakpoint mapped centromeric to Bat-2 (D17H6S51E). In recombinant strains B6.R4, B6.AK1 and B10.BYR1, recombination occurred within or close to the Bat-5 (D17H6S82E) locus. The immunogenicity of B10.BYR1 and B6.R4 bone marrow cell (BMC) grafts differs from that of both sets of parents, as if genes at or just centromeric to Bat-5 are involved. The phenotype of B6.AK1 BMCs (Kb Dk) is similar to that of the H2k parent suggesting no changes occurred. However, RNA blot analysis has shown that the Bat-5 gene is expressed well in bone marrow cells of B10.BR mice but not in B6.AK1 marrow cells. Analysis of a limited number of tumor cells of hemopoietic origin identified a single transcript for Bat-5. Our present data identify a recombinational hot spot at the Bat-5 locus. The expression of Bat-5 or a nearby gene may influence the immunogenicity of BMCs.