A floxed neomycin resistance gene, as well as the VDJ 564 region from a hybridoma derived from an autoimmune SWRxNZB mouse, replaced a segment of DNA including DQ52 and the entire JH region. Male chimeric mice were bred to C57BL/6 females. The resulting offspring were crossed with cre expressing transgenic mice in order to excise the neomycin resistance cassette. (personal communication)