Immunological detection of Chinese hamster ovary cells expressing a multidrug resistance phenotype.

A monoclonal antibody (IgG1) has been prepared that specifically detects Chinese hamster ovary cells expressing a multidrug-resistant phenotype. This antibody recognizes the membrane P-glycoprotein (Mr 170,000) associated with drug resistance as determined by enzyme-linked immunosorbent assay with purified P-glycoprotein and by Western blot analysis of cell extracts from drug-resistant and drug-sensitive cells. By immunofluorescence methods, the antibody also reacts strongly with viable and ether:ethanol-fixed resistant cells but does not react with the parent drug-sensitive cell line. Thus, this antibody can bind with live cells allowing discrimination by immunohistochemistry between drug-resistant and drug-sensitive Chinese hamster ovary cells.