Isolation and sequence of sheep immunoglobulin E heavy-chain complementary DNA.

A complementary DNA (cDNA) corresponding to sheep immunoglobulin E heavy (IgE H) chain messenger RNA (mRNA) was isolated and sequenced. A fragment of sheep IgE constant H (epsilon)-chain was initially synthesized using the polymerase chain reaction (PCR) and single-stranded cDNA prepared from the mRNA of parasite-stimulated sheep lymph nodes. This fragment was then used to probe a cDNA library, again prepared from a parasite-stimulated lymph node. A recombinant clone containing cDNA encoding a sheep IgE H-chain of 1802 base pairs was isolated and the H-chain cDNA-sequenced. The nucleotide sequence was found to code for a complete sheep IgE H-chain, consisting of both variable (V) and constant (C) regions. When the amino acid sequence derived from the nucleotide sequence was compared to other species epsilon-chains, interesting homologies and differences between corresponding domains were found, including conservation in cysteine and tryptophan residues and variable glycosylation sites.