CELLULAR REQUIREMENTS FOR FORMATION OF EA ROSETTES BY HUMAN MONOCYTES

Abstract

The binding of sensitized red cells to Fc receptors in human monocytes was studied by evaluating the effects of various pharmacological reagents and other treatments on EA [erythrocyte, antibody] rosette formation. Cytochalasin B and 2-deoxyglucose inhibited rosette formation in a dose-dependent manner. Sodium azide and incubation at 4.degree. C also inhibited rosette formation, while incubation at 37.degree. C increased numbers of RBC [erythrocytes] bound to the monocytes. The microtubular poisons vinblastine and colchicine at high concentrations resulted in decreased adherence of monocytes and inhibition of rosette formation, while at low concentrations of colchicine, enhanced rosette formation was sometimes observed. Contrary to the effects on rosette formation, binding of [125I] Ig[immunoglobulin]G to monocyte monolayers was not altered by treatment of the monocytes with drugs. Mg ions were required to promote monocyte adherence, but Mg and Ca were needed for the best rosette formation. Apparently the formation of EA rosettes is dependent not merely on binding of IgG to the Fc receptor but requires metabolically active monocytes, an intact cytostructure and suitable environmental conditions (temperature and cation concentration).