A simple quantitative immunofluorescence assay for FITC-labeled antibody on platelets.

A quantitative immunofluorescence technique is described which uses platelets as object cells and fluorescein isothiocyanate as a fluorescent label. The problem of light scattering and fluorescence quenching was resolved by solubilization of platelets using sodium dodecyl sulfate. This treatment did not disturb the linear correlation between fluorescence and concentration of FITC. Antigen-antibody reactions did not alter the fluorescence of FITC. Solubilized platelets did not lower the sensitivity of fluorimetry. Fluorimetry on platelets from idiopathic thrombocytopenic purpura gave results consistent with other assay methods.