A cell ELISA for the quantitation of leukocyte antigens. Requirements for calibration

A cell ELISA for human leukocytes has been established and standardized. The assay was based on the use of air-dried and methanol-fixed cells which were attached to microplate wells. Cellular antigens were measured through the subsequent binding of monoclonal antibody (MoAb), biotinylated sheep Ig against mouse IgG and streptavidin-peroxidase conjugate. The test was standardized by measuring both the specific antigen and the amount of cellular protein in each single sample and was calibrated either with intact cells or isolated plasma membranes prepared from the cells under study. The detection of the pan T-lymphocyte-specific 3A1 antigen (CD7, P40) in fewer than 5000 cells or less than 50 ng membrane protein was possible.