DEVELOPMENT AND APPLICATION OF A SENSITIVE RADIOIMMUNOASSAY FOR HUMANGRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR ABLE TO MEASURE NORMAL CONCENTRATIONS IN BLOOD

A radioimmunoassay (RIA) for human granulocyte-macrophage colony-stimu lating factor (GM-CSF) was developed based on antibodies from rabbits immunized with glycosylated recombinant human (rh) GM-CSF. The antibod ies are specific for human GM-CSF and do not crossreact with other hum an hematopoietic growth factors or mouse GMCSF. The antibodies also re act with nonglycosylated rhGM-CSF, so E. coli-derived rhGM-CSF can be assayed as well. The RIA has a measuring range of about 10 to 200 pg/m L. Normal blood was found to contain 13 to 24 pg/mL (95% limits) with a mean of 18.5 pg/mL (n=34). Monoclonal antibodies against GM-CSF coul d remove GM-CSF from normal human serum, thus ensuring that the GM-CSF measured in serum is real and does not represent nonspecific reactivi ty with our polyclonal rabbit antibodies. While previously published m ethods have been unable to measure GM-CSF in human serum under normal conditions, our more sensitive RIA does confirm the presence of small amounts of GM-CSF in serum or plasma and can therefore be used to dete ct fluctuations of GM-CSF in health and in disease.