The iLite® G-CSF Assay Ready Cells can be used for the quantification G-CSF activity and G-CSF inhibitor activity, either in buffer systems or human serum. Granulocyte-colony stimulating factor (G-CSF or GCSF), also known as colony-stimulating factor 3 (CSF 3), is a glycoprotein that stimulates cells in the bone marrow to differentiate into granulocytes which are subsequently release into the blood. The G-CSF-Receptor is present on precursor cells in the bone marrow, and, in response to stimulation by G-CSF, initiates proliferation and differentiation into mature blood cells. Different types of pharmaceutical analogs are used as a therapeutic agent to stimulate the bone marrow to produce more neutrophils (white blood cells) to fight infection in patients undergoing chemotherapy for cancer.