HSCs engraft long term in MHC-matched but not MHC-disparate recipients. (A) Degree of MHC matching between donor and recipient is shown. The shading denotes the genetic disparity between B10.BR HSC donor and recipients (□ indicates k haplotype; ▨, b haplotype). (B) Kaplan-Meier survival curves of recipients of 5000 syngeneic HSCs (B10.BR → B10.BR); MHC-matched but minor antigen–mismatched (B10.BR → AKR); and MHC-disparate but minor antigen–matched (B10.BR → C57BL/10) HSCs following conditioning with 950 cGy TBI. P values denote significance estimates.