| Abstract: | Remarkable similarities in the intracellular and genetic events occur when lymphoid and hematopoietic cells are exposed to their specific growth factors. The interleukin-2 (IL-2) receptor, whose cell-surface expression is an absolute requirement for the growth and differentiation of lymphoid cells, was detected on various nonlymphoid hematopoietic cell types in this study. Cell lines consisting either of granulocyte-macrophage precursors or mast cells, which are dependent on interleukin-3 (IL-3) for their growth, expressed high levels of the IL-2 receptor on their surface. Analysis of the binding characteristics of these receptors with 125I-labeled recombinant IL-2 revealed that only receptors with low affinity for IL-2 were present on these cells. Addition of purified recombinant IL-3 to these cell lines led to an increase in IL-2 receptor gene expression within 1 hour in isolated nuclei. This IL-3--induced increase in the number of IL-2 receptors on the cell surface is maximal within 24 hours. Addition of 10,000 units of IL-2 to these cells had no apparent effect on their growth or differentiation. The presence of the receptor with only low affinity for IL-2 on hematopoietic cells and the regulation by IL-3 suggest that this receptor is involved in some important metabolic event in hematopoiesis. |
