Table III.

Recombinant IFN-β is sufficient to prevent the establishment of hematopoietic chimerism and transplantation tolerance in mice treated with costimulation blockade

Group	IFN-β	Chimerism Frequency	Donor origin PBMCs at 8 wk (%)	MST of Skin Grafts in Transplanted Mice (days)	MST of Skin Grafts in Nonchimeric Mice (days)	MST of Skin Grafts in Chimeric Mice (days)
1	None	6/10 (60.0%)	1.98 ± 2.34	>252	35	>252
2	5.0 × 104 U	1/3 (33.3%)	2.65	>252	181	>252
3	7.5 × 104 U	0/4 (0.00%)*	<0.10	36#	36	N/A

^aC57BL/6 mice were treated with BALB/c DST, anti-CD154 mAb, and transplanted with BALB/c bone marrow and skin according to our standard protocol. Mice treated with rIFN-β were given an i.p. injection of the indicated amount on day −7 relative to bone marrow cell and skin transplantation. Hematopoietic chimerism was defined as >0.10% donor origin PBMCs 7–8 wk after bone marrow injection. The percentage of donor origin PBMCs is the mean ± SD percentage of the levels observed in chimeric mice. For groups with no chimeric mice, we used the limit of detection (<0.10) to indicate a lack of chimerism.

^*p < 0.05 vs group 1 by unpaired t test

^#p < 0.05 vs group 1 by log-rank analysis.

N/A, not applicable.