Hierarchical down-modulation of hemopoietic growth factor receptors

Abstract

Granulocytes and macrophages can be produced in vitro when progenitor cells from mouse bone marrow are stimulated by any of four distinct colony stimulating factors, Multi-CSF (IL-3), GM-CSF, G-CSF, and M-CSF (CSF-1). At 0°C the four CSFs do not cross-complete for binding to bone marrow cells, indicating that each has a specific cell surface receptor. However, at 21°C or 37°C, Multi-CSF inhibits binding of the other three CSFs and GM-CSF inhibits binding of G-CSF and M-CSF. Rather than competing directly for receptor binding, the binding of Multi-CSF, GM-CSF, or G-CSF to their own receptor induces the down-modulation (and thus activation) of other CSF receptors at 37°C. The pattern and poten..