Species and Strain Dependence of the Response to a Granulocytosis-Promoting Factor (GPF) Extracted from a Mouse Tumor. ∗

Abstract

Summary

Marked strain differences were observed in the degree of granulocytosis which could be induced in both mice and rats by a partially purified granulocytosis - promoting factor (GPF) extracted from a transplantable mouse tumor, CE 1460. The strain differences appeared to be reflected in both the normal leukocyte range and the response to isotonic saline, parameters from which the strain-specific response to GPF could apparently be predicted. It was postulated that the active principle in GPF may be the same as that present in “leukopoietin” preparations from plasma and tissue sources. Furthermore, it was hypothesized that the greater granulocyte release promoted by GPF, as compared to that promoted by “leukopoietin”-rich preparations, might conceivably be due 1) to species or strain differences in the bioassay systems or 2) to a greater concentration of the active (granulocytosis-promoting) principle and/or a lower concentration of a theoretical granulo-cyte-release inhibiting substance in the partially purified GPF prepared by our method or 3) to a combination of these factors. These results indicate that genetic (strain and species) differences should be taken into consideration in evaluating the biologic activity of GPF and possibly also of “leukopoietin.”