Fc epsilon receptor, a specific differentiation marker transiently expressed on mature B cells before isotype switching.

Abstract

The expression of Fc.epsilon.R on human lymphocytes was studied with the anti-Fc.epsilon.R mAbs. Fc.epsilon.R was expressed on most .mu.+,.delta.+ circulating B cells, whereas T cells did not express Fc.epsilon.R even in patients with hyper-IgE syndrome. B cells with .gamma., .alpha., or .epsilon. phenotype did not express Fc.epsilon.R, moreover its expression could not be induced, suggesting that the Fc.epsilon.R expression was correlated with isotype switching. .mu.+.delta.+ B cells in bone marrow did not express Fc.epsilon.R, but PHA-sup (supernatant from PHA-stimulated cell cultures) could induce its expression, and the addition of IgE augmented this induction. Recombinant IL-2, IL-1, IFN-.gamma. or -.beta., or purified B cell differentiation factor (BSF-2 B cell-stimulatory factor 2) could not induce Fc.epsilon.R exprssion in bone marrow B cells. IFN-.gamma. inhibited the Fc.epsilon.R expression induced by PHA-sup, suggesting that the human counterpart of BSF-1 may be responsible for Fc.epsilon.R expression in bone marrow B cells. B cells from patients with common variable immunodeficiency and ataxia teleangiectasia did not express Fc.epsilon.R, but PHA-sup could induce its expression, indicating that circulating B cells of these patients are at a differentiation stage similar to B cells in bone marrow. The study showed that Fc.epsilon.R is a B cell-specific differentiation marker, the expression of which is restricted to a defined stage of B cell differentiation.