Donor-specific tolerance in vitro and in vivo in chimeric sensitized recipients. Presensitized chimeras (B10.BR → B10 and BALB/c → B6) were evaluated for donor-specific tolerance in vitro by MLR and in vivo by allogeneic skin grafts. (A) Splenocytes from chimeras (n = 3) were stimulated with irradiated host, donor, and third-party stimulator cells in MLR assay. Values are shown as the mean ± SD of triplicate cultures in a 1:1 responder/stimulator ratio from representative chimeras (BALB/c → B6). The stimulation index (SI) reflecting the ratio of the value to the autoresponse is shown at the bottom of the figure. (B) Life table survival of donor and third-party skin grafts in sensitized chimeras. B10.BR → B10 or BALB/c → B6 chimeras each received skin grafts from B10.BR and BALB/c donors as donor-specific (n = 7) or third-party (n = 7) grafts 2 to 4 months after BMT. Grafts were monitored for 200 days.