Detection of oncostatin M in human plasma and serum by a sensitive enzyme immunoassay

A sensitive and specific enzyme immunoassay was developed for detecting oncostatin M (OM) in human plasma and serum. The assay utilizes three anti-OM monoclonal antibodies that recognize mutually exclusive epitopes, including a neutralizing epitope. A sensitivity of 24 pg/ml was routinely obtainable. The assay showed no cross-reactivity with leukemia inhibitory factor (LIF) or interleukin-6 (IL-6), other members of the cytokine family that includes OM. The utility of the enzyme immunoassay (EIA) was demonstrated by detecting the time-dependent accumulation of OM in plasma from lipopolysaccharide (LPS)-treated human whole blood. The concentration of OM in human sera from normal donors was generally below the detection limits of the assay. However, concentrations of OM greater than 25 pg/ml were found in 17 of 212 serum samples from apparently normal donors. The detection of OM in human plasma and serum demonstrates that the EIA could be a useful tool in examining the role of OM in physiologic and pathologic states.