ELEVATION OF LYMPHOCYTE AND HEMATOPOIETIC STEM-CELL NUMBERS IN MICE TRANSGENIC FOR HUMAN GRANULOCYTE CSF

Transgenic mice expressing human granulocyte colony stimulating factor (hG-CSF) were bred to establish an experimental model for studying th e biologic function of hG-CSF. The mice produced approximately 1000 pg /ml of hG-CSF in sera and expressed hG-CSF mRNA in all of the tissues examined. Granulocytosis and elevation of hematopoietic precursor numb er were observed in hematopoietic tissues as expected, but lymphocytos is with 5-fold increase in peripheral blood and 2-fold increase in spl een was also evident. Hematopoietic stem cells capable of reconstituti ng lethally irradiated recipient mice were abundant in the circulation of these transgenic mice. No disadvantageous tissue damage was observ ed when various organs were analyzed. As shown in this study, G-CSF ha s a stimulating effect on lymphopoiesis when it is expressed in a cert ain condition. The lymphocytosis, as well as the high level of hematop oietic stem cell mobilization into circulation, indicates a wider rang e of potential G-CSF activity than expected. The mice transgenic for h G-CSF described herein will contribute greatly to the understanding of the regulatory mechanism in hematopoiesis.