Table 2.

Summary of binding characteristics of class I and class IV isoforms

	Ba/F3 G-CSFRI		Ba/F3 G-CSFRIV
	Kd (nM)	Number of sites/cell	Kd (nM)	Number of sites/cell
Average	0.58±0.02	10 267±834	0.53±0.04	9996±1812

Abbreviation: GCSFR, granulocyte colony-stimulating factor receptor. Binding affinities (Kd) and receptor numbers (sites/cell)±s.e.m. were determined from independent steady-state binding experiments, using radiolabeled hGCSF and Ba/F3 cells expressing either class I or class IV GCSF receptor. The values were determined as an average of values obtained from three independent experiments and by using nonlinear regression analysis as done in Figure 3a.