Table 1.

PD-1 is required to prevent rejection of male islet grafts in sensitized recipients.

Group	Islet Donor	Recipients	Anti-PD-1 treatment	Graft Survival (d)	% Graft survival
1	Male	PD-1−/−	N/Aa	10 × 2, 14, 18, 20 × 2, 28, 76b	0
2	Female	PD-1−/−	N/A	> 100 × 5	100
3	Male	BTLA−/−	None	44, > 100 × 3	75
4	Male	WT	None	> 100 × 7	100
5	Male	WT	At Immunization	15, 16, > 100 × 3	60
6	Male	WT	At Transplantation	20, > 100 × 4	80
7	Male	WT	At Immunization & Transplantation	17, 19, 28, > 100	25

Female WT or PD-1^−/− or BTLA^−/− mice were immunized with male splenocytes two weeks before transplantation of islet grafts. The sensitized PD-1^−/− mice given male islets (group 1) were significantly different (P< 0.01) from groups 2, 3, and 4. For groups 5–7, female WT mice were treated with anti-PD-1 at the time of immunization with male splenocytes or at the time of transplantation of male islets, 2 weeks after immunization or at both stages. Group 7 vs. 4 (P> 0.05).

^aN/A, not applicable

^bGroup 1 recipients (n=8) of male islets received islets from WT B6 (n=4) or PD-1^−/− B6 (n=4) donors.