Due to the Yaa translocation on the Y Chromosome, BXSB/MpJ males (Stock No. 000740) develop a spontaneous lupus-like autoimmune syndrome. The first deaths occur at approximately 13 weeks of age with 50% lethality by approximately 30 weeks and 76% lethality by approximately 40 weeks. BXSB/MpJ females develop a greatly attenuated form of autoimmune disease because they lack Yaa. Bubier et al. (2009) determined that interleukin 21 signaling to B cells is essential for this autoimmune response and that BXSB/MpJ males homozygous for the Il21rtm1.1Hm null allele do not develop the hypergammaglobulinemia, autoantibody production, or other autoimmune disease phentoypes that occur in BXSB/MpJ males and in BXSB/MpJ males heterozygous for the Il21rtm1.1Hm null allele. Rather these homozygotes are viable and fertile with a lifespan usually exceeding 40 weeks of age. This strain is valuable for the assessment of the role of IL21 signaling in this autoimmune disease and has been used to delineate the cell types and interactions essential for the development of this autoimmune disorder (McPhee et al., 2013).
