The bovine interleukin-4 gene: genomic organization, localization, and evolution.

Interleukin-4 (IL4) is involved in the immune response to certain parasites and possibly in the development of some atopic diseases since it triggers the T helper 2 lymphocyte response. Therefore, IL4 is a candidate gene, for example, for disease association studies and gene mapping. We isolated bovine IL4 cosmids and determined the genomic organization. Fragments carrying the exons as well as 725 base pairs (bp) from the 5' flanking and 190 bp from the 3' flanking region were cloned and sequenced. The first 481 base pairs of the 5' flanking region, including the putative promoter sequences, are surprisingly similar (92%) between cattle and human. In addition, we cloned and sequenced a mixed [(t/g)a]m(ca)n repeat located approximately 35 kilobases upstream from the IL4 gene. It showed seven repeat length alleles in a limited number of animals. The IL4 gene has been assigned to 7q15-q21 by fluorescence in situ hybridization in cattle. Evolutionary aspects are discussed on the basis of sequence data as well as interspecies chromosomal homologies.