Alternative RNA of Epsilon Transcripts Produces mRNAs Encoding Two Membrane and Four Secreted IgE Isoforms

We elucidated a series of alternatively spliced human epsilon mRNAs by employing a human epsilon-specific RT-PCR strategy. Two mRNA isoforms provide for the expression of distinct membrane IgE proteins, the common form of which contains a novel 56-amino-acid sequence after the last epsilon constant-region domain. Other mRNAs encode, in addition to the classic secreted epsilon chain, at least three novel epsilon secreted proteins that lack a transmembrane domain and possess distinctive C-terminal features. Furthermore, the expression of these epsilon mRNA isoforms is differentially regulated by stimuli such as interleukin-10, Fc epsilon RII cross-linking and aromatic hydrocarbons found in diesel exhaust.