A highly sensitive enzyme immunoassay for G-CSF in human plasma

We have developed a sensitive sandwich enzyme-linked immunosorbent assay (ELISA) to measure granulocyte colony-stimulating factor (G-CSF) in human plasma. This ELISA employs a combination of a mouse monoclonal antibody (MAb) as the first antibody and an affinity-purified sheep polyclonal antibody conjugated with beta-D-galactosidase as the second antibody. The coefficients of intra- and interassay variations were 2.2 to 3.6% and 8.3 to 10.2%, respectively. The assay had no cross-reactivity with four other human cytokines. Plasma G-CSF levels in healthy volunteers could easily be measured because the detection limit was 0.5 pg/mL. The mean plasma G-CSF concentration in 57 healthy volunteers (aged 19 to 47; 27 males and 30 females) was 10.5 +/- 4.5 pg/mL standard deviation [SD]). There was no statistically significant relationship between plasma G-CSF concentration and absolute neutrophil counts in those healthy volunteers (r = 0.259; p = 0.052).