Re-examination of the EA rosette assay (Ripley) for Fc receptor leucocytes.
Numerous investigations has utilized rosette formation with Ripley antibody-coated human erythrocytes (EA) to identify or deplete Fc receptor-bearing K lymphocytes in whole mononuclear cell preparations. This study examines the interaction between Ripley EA and purified preparations of human lymphocytes, monocytes and neutrophils and demonstrates that this technique is not specific for K lymphocytes. Indeed, 100% of blood monocytes rosette these EA target cells. Moreover, data from both rosetting studies and antibody-dependent cytotoxicity (ADCC) reactions suggest that the avidity of Ripley EA is actually greater for monocytes than for lymphocytes. In contrast to previous reports, 100% human neutrophils were found to possess Fc receptors, as determined by their ability to rosette Ripley EA. Thus, the extent of rosetting and ADCC by all three Fc receptor-bearing leucocytes depends significantly on the degree of antibody sensitization with neutrophils requiring the greatest, and monocytes the least, amount of target-bound antibody for Fc receptor-mediated interaction.