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.