An enzyme immunoassay for the measurement of HLA-DR antigen expression

A simple, sensitive, rapid and reproducible method is described for the measurement of HLA-DR expression on monocytes. The assay is based on an enzyme-linked immunostaining of the cells in suspension form followed by colour development. The non-specific binding of anti-HLA-DR to Fc receptors was taken into account by incubation of cells with an irrelevant monoclonal antibody (antirubella-G7H9). The binding of the anti-rubella monoclonal with the cells was subtracted from the binding of anti-HLA-DR to cells. Using three different cell lines (K562, CTLL and Daudi), the specificity of the assay proved to be acceptable and the assay remained sensitive even when only 10(4) cells/well were used. The assay has a number of potential applications.