Alternative transcripts of the human CD23/FcϵRII

Abstract
Human CD23/FcϵRII is a 45 kDa type-II membrane glycoprotein having two isoforms (a and b) that only differ in the structures of their intracytoplasmic tails. CD23/FcϵRII has been demonstrated to have multiple roles in the immune system such as regulation of lymphocyte growth and differentiation and IgE-mediated immune responses. Here, we found that the human B-cell line RPMI8866, in addition to a and b transcripts, contained shorter transcripts (a' and b') that lack the entire third exon. These alternative transcripts were also detected in peripheral blood lymphocytes as well as other hematopoietic cell lines with CD23/FcϵRII. Because exon 3 encodes all of the transmembrane segment and the anchoring region of the cytoplasmic tail, it is suggested that a' and b' transcripts encode secretory forms of CD23/FcϵRII or they may function as regulatory transcripts involved in the control of CD23/FcϵRII expression.