A comparison of EA-Rosette formation on lymphocytes using rabbit and human sensitizing antibodies

The IgG receptors of peripheral blood lymphocytes were studied to determine whether those detected by a rabbit anti-ox erythrocyte antibody (EARa) and a human anti-human erythrocyte antibody (EAHu) were the same. With cells separated by Ficoll-Hypaque and freed of adherent cells by exposure to plastic surfaces, both EA systems gave similar numbers of rosettes. Mixed rosetting occurred when both types of sensitized cells were added simultaneously. EAHu and EARa rosettes showed similar kinetics of formation. Depletion of rosette-forming lymphocytes was possible by using both systems, and depletion by one system showed depletion in the other. sIg-bearing lymphocytes were also removed, the amount of depletion being dependent on the degree of RBC sensitization with antibody. EAHu and ERRa rosettes were equally inhibited by IgG of a given species of subclass. Normal human and rabbit IgG were more inhibitory than bovine or guinea-pig IgG. All of the human subclasses inhibited, but IgG and IgG3 were more inhibitory than IgG and IgG4. These results indicate that Fc gamma receptors on human lymphocytes react with an IgG configuration that is present on IgG of many species, although it is variably expressed among them. Human IgG1 and rabbit IgG are equivalent in the system and can be used equally well to detect Fc IgG-receptor-bearing cells.