Characterization of caprine interleukin-4

Caprine interleukin-4 (IL-4) cDNA was cloned from RNA of mitogen stimulated goat peripheral blood mononuclear cells utilizing reverse transcriptase–polymerase chain reaction. The sequence of caprine IL-4 cDNA corresponds to a 535 nucleotide mRNA with 5′- and 3′-untranslated regions and a 405 nucleotide open reading frame, the first 66 nucleotides of which encode a putative signal peptide. Mature IL-4 is a 12.8 kDa protein containing six cysteine residues and two potential N-linked glycosylation sites and is highly homologous with other ruminant IL-4. The predicted molecular mass of mature unglycosylated IL-4 was confirmed by western blot of recombinant caprine IL-4 expressed in bacteria with a monoclonal antibody against a carboxyterminal peptide derived from the predicted amino acid sequence of bovine IL-4. Eukaryotic expression plasmids containing caprine IL-4 cDNA were used to characterize recombinant IL-4. Transcription of IL-4 mRNA was confirmed by transfection of COS-7 and goat synovial membrane cells, and recombinant IL-4 produced by stably transfected L929 cells inhibited inducible nitric oxide synthase in macrophages. Genetic immunization of mice with a caprine IL-4 cDNA expression plasmid induced antibodies against recombinant caprine IL-4 produced in bacteria.