Molecular cloning, sequencing, and expression of equine interleukin-6

Equine interleukin-6 (IL-6) cDNA was amplified from mitogen-stimulated equine peripheral blood mononuclear cells (PBMC) using consensus sequence primers. The 727 bp amplified cDNA contains the entire coding region for equine IL-6 and includes 118 bases in the 3′ non-translated region. The coding sequence translates to a protein of 208 amino acids with a predicted 28 amino acid leader sequence. The mature protein of 180 amino acids has a predicted molecular mass of 20 471 Da without post-translational modifications. The amino acid sequence of equine IL-6 displays between 46 and 84% similarity to other mammalian IL-6 sequences. Expression of equine IL-6 in Chinese hamster ovary (CHO) cells yielded a supernatant that supported the proliferation of B9 cells in a dose-dependent manner. Treatment of B9 cells with an anti-IL-6 receptor antibody ablated the response to the recombinant equine IL-6.