Daily administration of oral WGP β-glucan significantly enhances the recovery of peripheral blood leukocytes following sublethal irradiation in a CR3-dependent manner. Groups of 6 WT (—) or CR3^-/- (- - -) were sublethally irradiated with 500 cGy of TBI from a cesium-137 source, and the leukocyte nadir was observed 5 days following irradiation. One day prior to irradiation, the mice were divided to receive no treatment (•), 0.1 mL oral phosphate-buffered saline (PBS; ▪), or 0.1 mL oral WGP β-glucan (0.8 mg/mL; ▾). Following irradiation, mice were treated as indicated daily for 3 weeks, during which time peripheral blood was collected by retro-orbital venipuncture at the indicated intervals for analysis by manual counting by investigators who were blinded to the treatment arms. WT, but not CR3^-/-, mice receiving oral WGPs were observed to have a significantly accelerated recovery of peripheral blood leukocytes 7 and 11 days following irradiation compared with their counterparts receiving PBS (^*P < .05; ^***P < .001). All animals had normal peripheral blood leukocyte counts 3 weeks following irradiation. The data shown here are 1 representative experiment (6 mice in each group) of 3 separate experiments.