ALLOGENEIC PERIPHERAL-BLOOD PRECURSOR CELL TRANSPLANTS IN RABBITS

This report summarizes a series of experiments undertaken to evaluate the role of mobilized peripheral blood precursor cells (PBPC) for tran splantation across a major histocompatibility barrier, Adult outbred r ed Burgundy rabbits were used as donors, New Zealand white rabbits of the opposite sex as recipients, Conditioning consisted of single dose total body irradiation (TBI) of 10 Gy supported by a short course of c yclosporine to enhance engraftment. Human recombinant G-CSF at a dose of 10 mu g/kg was used for mobilization of precursor cells, Three meth ods of PBPC transplants were tested initially in 5 animals each, PBPC were collected and infused at once on day 0; collected initially, cryo preserved for one month, infused on day 0 and followed by 3 additional fresh donations or collected and infused on 6 occasions between days 0 and +11. 13 animals engrafted, 2 became complete, longterm chimeras, Survival was best in the group given repetititive infusions (39 days median, 12 days to > 180 days, range), 10 additional animals were tran splanted as in the last group and the number of transplanted nucleated cells (10.5 x 10(8)/kg median, 7.3 - 15.7 x 10(8)/kg range) and colon y forming units CFU-GM (42 x 10(4)/kg median, 12.3 - 176.8 x 10(4)/kg range), were compared with outcome, Median survival of the 10 animals was 29 days (12 - 55 days range; 1 autologous reconstitution). Surviva l did not correlate with total nucleated cells per kg (r = 0.10; p = 0 .79), but there was a trend to prolong survival with higher numbers of CFU-GM per kg (r = 0.47; p = 0.19), These data show that allogeneic P BPCT can engraft across a major histocompatibility barrier, that the h igh number of CFU-GM per kg might be advantageous, but also that addit ional methods are warranted to reduce acute GvHD.