Effect of prior NK activation of recipient mice with β2m^−/− BMC rejection. Two and 1 days before transplantation B6 recipient mice were treated with anti-NK1.1 (PK136), anti-Ly49G2 (4D11), anti-Ly49C/I (5E6), or rIgG control. In addition, some mice received poly I:C 2 days before BMT to boost BMC rejection. A total of 25 million β2m^−/− BMCs were injected into lethal irradiated B6 recipients. The CFU-c formation from the spleens is shown (mean ± SEM). One-way ANOVA test was performed to determine whether the mean values were significantly different (P < .05). Each experiment was performed 2 or 3 times.