Improved ELISA proliferation assay (EPA) for the detection of in vitro cell proliferation by a new Ki-67-antigen directed monoclonal antibody (Ki-S3).

We describe a simplified and improved proliferation assay based on a conventional ELISA system for the in vitro measurement of cellular proliferation (ELISA proliferation assay = EPA). The assay is based on a new monoclonal antibody (Ki-S3) to the proliferation-specific Ki-67-antigen and is carried out in 96-well microtiter plates using conventional immunoenzymatic methods. Ki-S3 is an immunoprecipitating monoclonal mouse IgG1 antibody, which recognizes a formalin-resistant epitope of the Ki-67 antigen. It can be used to measure proliferating cells in the cell cycle phases G1, S, G2 and M. In phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMC) the absorbance values obtained with the EPA show a statistically significant correlation to the number of Ki-S3 positive cells in simultaneously immunostained cytospin slides (r = 0.88). A direct comparison with [3H]thymidine labeling reveals the test to be an equally sensitive method for monitoring cellular proliferation (r = 0.91). This assay is an improved ELISA proliferation assay, which is easy to perform, does not require time-consuming pretreatments and avoids the hazards of radioactive isotopes.