The low affinity IgE Fc receptor (CD23) participates in B cell activation.

Abstract

The low affinity IgE Fc receptor (FcɛRII or CD23) is expressed on all mature B lymphocytes (reviewed in 1 and 2). The FcʵRII is a 45 to 49 KD glycoprotein, and is categorized as a class II transmembrane molecule on account of its inverted membrane orientation. In addition to the transmembrane form of the receptor, a soluble form is readily released from B cells, a result of cleavage by a cell surface protease. cDNA cloning has revealed that the FceRII is a member of the hepatic lectin family, a somewhat unusual finding since all other characterized Fc receptors are known to be members of the immunoglobulin (Ig) gene superfamily.