Ultrafiltered Pig Leukocyte Extract (UPLE, IMUNOR®) Potentiates Hematopoiesis–Stimulating Effects of G-CSFIn Vitroand Improves the Outcome of Treatment of Hematopoietic Radiation Damage in Mice with G-CSF

Ultrafiltered pig leukocyte extract (UPLE, Imunor), a heterogeneous mixture of low molecular weight (<10 kD) substances released from disintegrated pig leukocytes was tested from the point of view of its hematopoiesis-modulating activities using experiments in vitro and in vivo. Attention was focused especially on evaluation of the contingent ability of UPLE to potentiate the hematopoiesis-stimulating effects of recobinant human granulocyte colony-stimulating factor (G-CSF). Experiments in vitro revealed the capability of sera from mice administered UPLE perorally (p.o.) to stimulate proliferation of progenitor cells for granulocytes and macrophages (GM-CFC) in cultures of normal bone marrow cells. In addition, UPLE, as well as sera from mice given UPLE, added to the cultures in combination with G-CSF enhanced the numbers of GM-CFC significantly over those induced by sera after administration of either of the preparations alone. In in vivo experiments, UPLE was found to increase the counts of GM-CFC per femur and femoral bone marrow cellularity in sublethally irradiated mice when administered p.o. after irradiation in combination with G-CSF in comparison with the effects of G-CSF alone. These results indicate the possibility of using UPLE, a commercially available preparation, for treatment of hematopoietic suppression of various etiology.