A subpopulation of normal human peripheral B lymphcytes that bind IgE.

Isolated normal human peripheral lymphocytes were analyzed for their ability to bind IgE as shown by rosette formation with aldehydefixed ox red cells coated with an IgE myeloma protein (Eo'-IgE) as indicator cells. An average of 4.3% of the cells in the lymphocyte preparations of 12 donors formed Eo'-IgE rosettes. The lymphocyte preparations contained an average of 0.36% basophils which also formed Eo'-IgE' rosettes, suggestiing that about 4% of the lymphocytes bound IgE. The rosette formation was inhibited by IgE myeloma protiens or IgE Fc fragments but not by IgE Fab fragments or Ig of the other classes. On the average, the lymphocytes of the 12 donors contained 70.5% cells forming spontaneous rosettes with sheep erythrocytes (E), 10.6% cells having surface immunoglobulin (SIg), and 15.5% bunding IgG as shown by rosette formation with IgG-coated ox red cells (EoA). Fractionation of the lymphocytes into populations rich in spontaneously E-rosetting cells and cells with SIg indicated that the majority of the lymphocytes forming Eo'-IgE rosettes belonged to the SIg-positive lymphocytes. Analyses of lymphocyte populations lacking cells forming EoA rosettes and of rosetting with mixed indicator cells both demonstrated that over 90% of the lymphocytes forming Eo'-IgE rosettes did not form EoA rosettes and apparently had no Fc receptors for IgG. Pretreatment of the lymphocytes with trypsin in amounts that did not alter the number of EoA-rosetting cells abolished the Eo'-IgE rosette formation. These data indicate that a subpopulation of normal human peripheral lymphocytes, probably belonging to the B-cell type, binds IgE presumably via trypsin-sensitive receptors specific for the Fc fragment of IgE. The surface markers of these lymphocytes resemble those of cultured human lymphoblastoid cells that have recently been shown to bind IgE.