Nucleotide sequence and restriction fragment length polymorphisms of the equine Cε gene

IgE is the dominant immunoglobulin isotype involved in type I hypersensitivities in mammals. The heavy chain constant region domains of equine IgE are encoded by a single gene, the Cε gene. By restriction analysis of cDNA from 15 unrelated horses, we have now identified two Cε alleles, characterised by a Sma I restriction fragment length polymorphism, which we designated Cεa and Cεb. Sequence analysis of both, Cεa and Cεb cDNA, showed in addition two single base exchanges resulting in two amino acid substitutions. Both sequences have only 95.9% homology of the coding region sequence with the published equine Cε sequence, which could represent a third haplotype. Polymorphism of the IgE heavy chain constant region gene, as described here, might well impose genetic variability on the effector functions of equine IgE predisposition to allergic diseases in horses.