Flow-cytometric detection of circulating immune complexes

Abstract In an effort to develop an assay which would rapidly detect and analyze circulating immune complexes, we have adapted the Raji cell radioimmunoassay (RIA) to a flow cytometric (FCM) analysis. The advantages of immune complex analysis by FCM are many. Foremost is the effectiveness and efficiency of the FCM method relative to the radioimmunoassay (RIA) method. The data demonstrated that FCM detection is three times more sensitive than RIA detection. Only populations of viable Raji cells bearing immune complexes are analyzed because parameters of the FCM analysis permitted the elimination (gating out) of dead cells. The determinations are rapid and the data are immediately available for several additional analyses. Because of the availability of many fluorescent monoclonal antibodies to complement components, viral antigens, light chains and immunoglobulin isotypes, it is possible to detect many components that might be present in the Raji cell bound complexes. Finally, the Raji cells can be characterized in different stages of their cell cycle to generate information about the state of the cells and the density of the receptors involved in binding the complexes.