Joint disease: It’s progressive, incurable, and widely prevalent among performance horses. Veterinarians can, however, provide affected horses with some relief in the form of conventional therapies, such as corticosteroids and/or hyaluronic acid injections or, in severe cases, biologic therapy. One such treatment is autologous conditioned serum (ACS), also called IRAP (interleukin-1 receptor antagonist protein).

At the 2015 American Association of Equine Practitioner’s convention, held Dec. 5-9 in Las Vegas, Dane Tatarniuk, DVM, MS, clinical instructor in equine surgery and sports medicine at the University of Minnesota’s College of Veterinary Medicine, in St. Paul, presented a study in which he and colleagues examined the composition of ACS—in particular an anti-inflammatory cytokine called the interleukin-1 receptor antagonist , or IL-1ra.

“There is prior evidence of this biologic therapy helping; however, the entire composition of ACS is unknown,” he explained. “Prior research has focused predominately on IL-1ra, however many proteins (both anti-inflammatory and pro-inflammatory) may be present within the therapy.”

But first, a little background on how ACS works. When a joint sustains injury, trauma stimulates the release of inflammatory proteins within the joint including IL-1 and other cytokines (proteins that signal cells to move toward inflammation sites). These accelerate and worsen inflammation, contributing to cartilage degradation that leads to an overall downward spiral of joint degeneration.

The objective in using ACS is to block the activity of interleukin-1 on joint tissues and