Chimerism after vascularized limb versus bone marrow transplantation

This study used quantitative PCR in the murine model to compare the ability of a limb allograft vs. a comparable dose of marrow suspension to induce chimcrism. Female C57B1/6 mice received a vascularized hindlimb allograft, a comparable dose of 5 × 10⁶ donor bone marrow cells, or a standard dose (20 × 10⁶) of marrow suspension from male Balb/c donors. All recipients were treated with a regimen based on CD40 costimulation blockade and T cell depletion. Y chromosome-specific quantitative PCR was used to measure chimerism. Most recipients of limb allografts demonstrated low levels of chimerism after 1 week (3/4) and 1 month (3/4). Most recipients of 5 × 10⁶ marrow cells had low levels of chimerism at 1 week (4/6) and only 1/5 after 1 month. All recipients of 20 × 10⁶ cells except one demonstrated either low or high levels of chimerism after 1 week (5/5) and 1 month (5/6). The marrow component of a limb allograft is thus more effective at inducing microchimerism compared to a comparable dose of bone marrow suspension.