Human lymphocytes isolated from adult peripheral blood and cord blood, tonsils, adenoids and spleens were analysed for Fc receptors for IgE (Fcepsilon) by rosette assays. The Fcepsilon+ cells were also characterized for their class of surface immunoglobulin (sIg), complement receptors, receptors for sheep erythrocytes (E), and Helix pomatia A haemagglutinin (HP), and their abilities to phagocytoze and adhere. The average number of Fcepsilon+ cells was in adult peripheral blood 1.2 +/- 0.4%, in cord blood 3.0 +/- 1.3%, in tonsils 4.2 +/- 5.2%, in adenoids 5.8 +/- 4.2%, and in spleens varied from 0.8% to 15.8% among individual patients. Overnight culturing of the lymphocytes under conditions that allowed detection of Fc receptors for IgM (Fcmu) usually lowered the number of Fcepsilon+ cells. Neuraminidase treatment caused no change. Rosette formation was inhibited by IgE myeloma proteins and their Fc fragments, but not by mildly reduced and alkylated and heated (56 degrees C) IgE, indicating that the receptors are specific for the native configuration of the IgE Fc fragment. Double cell surface marker analyses with fluoresceinated F(ab')2 fragments of purified anti-mu, delta, and gamma antibodies used to label the Fcepsilon rosette-forming lymphocytes from peripheral adult and cord blood showed that 50-80% were sIgM+ but only 0-28% were sIgD+. In contrast, approximately 80% of the Fcepsilon+ cells from tonsils, adenoids and spleens were sIgM+ and sIgD+. The Fcesilon+ lymphocytes represented 10-20% of the sIgM+ lymphocytes in both the peripheral adult and cord blood. Depletion and enrichment experiments indicated that most of the Fcepsilon+ cells bear complement receptors. Lymphocytes having both E and Fcepsilon receptors were not found. Furthermore, the lymphocytes with HP receptors, a marker for T cells and immature B cells, were Fcepsilon-. Monocytes and neutrophil granulocytes did not form Fcepsilon rosettes. These data indicated that a minor population of human B lymphocytes have Fcepsilon receptors. The majority of the Fcepsilon+ lymphocytes in the blood differ from those in tonsils, adenoids and spleen in that the majority of the former are sIgM+/sIgD- and the latter sIgM+/sIgD+. The sIgM+/sIgD- Fcepsilon+ cells in the blood are probably relatively mature lymphocytes since they lacked HP receptors, which are found on immature B cells.