Oral WGP β-glucan significantly enhances the survival of lethally irradiated mice that are rescued with an allogeneic WT, but not CR3^-/-, HPC transplantation. Two thousand WT or CR3^-/- C57BL/6 (H-2Kb) HPCs were transplanted into lethally irradiated (950 cGy) C3H/HeJ (H-2Kk) recipients. One group of recipients (n = 23) received daily oral WGP β-glucan (80 mg/kg) on days 1 to 10 after transplantation, and another group (n = 19) received saline. Groups of 10 recipients receiving CR3^-/- HPCs were treated similarly. (A) The treatment of recipient mice with oral WGP β-glucan (▾) resulted in a significant increase in survival 35 days after transplantation in mice receiving WT (—), but not CR3^-/- (- - -), HPCs (▪ indicates mice receiving HPCs but not WGP β-glucan). In addition, recipients receiving WT HPCs and oral WGP β-glucan were observed to have significantly enhanced survival with respect to recipients receiving only WT HPCs (^**P < .005; ^***P < .001). (B) Representative experiment of multilineage engraftment from a total of 7 mice. The data are 1 representative experiment of 2 separate experiments.