ACCELERATION OF GRANULOCYTIC CELL RECOVERY IN IRRADIATED MICE BY A SINGLE SUBCUTANEOUS INJECTION OF A HEAT-KILLED LACTOBACILLUS-CASEI PREPARATION

Flow cytometric analysis showed that the treatment of irradiated mice with a heat-killed Lactobacillus casei preparation (LC 9018) accelerat ed the recovery of granulocytic cell populations in peripheral blood, spleen and femur bone marrow. The recovery of the lymphocytic cell pop ulation was not accelerated while the recovery of the B-lymphocytic ce ll population was inhibited. Histological analysis also showed that th e LC-9018 treatment markedly enhanced granulopoiesis in the spleen and bone marrow of irradiated mice. The same LC-9018 treatment significan tly increased 30-day survival rates of athymic nude mice after lethal whole-body irradiation. The recovery of the granulocytic cell populati on in peripheral blood of irradiated athymic nude mice was also accele rated by LC-9018 treatment. Our results suggest that LC 9018 protected lethally irradiated mice from bone marrow death by enhancing granulop oiesis rather than lymphopoiesis and that the contribution of activate d T lymphocytes to the enhancement of the granulopoiesis was small.