Toxicity of spleen cell suspensions from heavily irradiated mice: implications for CFU-S seeding

Cell suspensions were made from spleens of mice 5 hr to 6 days after irradiation. Mice were irradiated with 800 rad. One group of mice received a transfusion of 2 x 106 nucleated bone marrow cells and another group no bone marrow transfusion. From 15 hr to 6 days after irradiation the toxicity of the cell suspensions varies with time and number of cells injected. As many as 20 x 106 spleen cells from normal mice or mice 5 hr after irradiation can be injected with no signs of toxicity. A molecular factor(s) in cooperation with cells or cell debris is responsible for the toxicity. Some characteristics of the factor(s) are described. The toxic cell suspensions caused pulmonary embolism. There was no effect of the toxic substance on pluripotent stem cells (CFU-S) in regular CFU-S assay or the ability of bone marrow to repopulate irradiated mice. Whether the emboli trap the CFU-S and influence the seeding efficiency of CFU-S in the spleen is not known