Genealogy of inbred mice used in this study. Aligned horizontally are the MHC donors for the congenic strains BALB.B, B10.BR, and BALB.K, which were C57BL/10J, C57BR/cdJ, and C3H/He mice, respectively, as indicated by dashed lines. B6 is the Thy1 C57BL/6 congenic strain expressing the Thy1.1 allele used as HSC donors for BALB.B mice in transplant experiments. The non-MHC background genes were of diverse origin as described in the text.