Granulocyte factors as potential haemopoiesis regulators in irradiated mice.

Protein substances stimulating lymphocytes in vivo and in vitro are present in the lysosomes and secondary granules of neutrophil granulocytes. The mechanism of this stimulation is probably dependent on blockade of T suppressor cell functions. These observations stimulated the present study undertaken to clarify the effect of granulocyte factors on the multipotential stem cells of the haemopoietic system in mice subjected to sublethal irradiation. The experiments were carried out on F1 hybrid (Balb/cx NMRI) mice receiving a whole body dose of 3 Gy irradiation. Granulocyte proteins were injected intravenously in doses of 6 micrograms per one mouse 18, 48 and 72 hours after irradiation. The assayed proteins increased the number of macroscopic and microscopic colony forming cells in the mice spleens. The increase of erythrocyte granulocyte index in colonies and decrease of lymphocyte granulocyte index in peripheral blood have been observed. In the light of these results it is concluded that lysosomal granules and secondary granules of neutrophils contain protein factors stimulating the regeneration of haemopoietic cells of the erythrocyte and granulocyte series in the irradiated mice spleens.