To combat joint disease or osteoarthritis in horses, many veterinarians have used autologous conditioned serum (ACS), also called by the product name IRAP (for the interleukin-1 receptor antagonist protein it contains), since the first scientific publication appeared on the subject in 2003. Since that time, a new kid on the block–a similar product sharing many characteristics with the original, and, indeed, named IRAP II–has arrived on the market. At the 2010 American Association of Equine Practitioners convention, held Dec. 4-8 in Baltimore, Md., a study comparing the two products was presented by David Frisbie, DVM, PhD, Dipl. ACVS, associate professor of Clinical Sciences at Colorado State University.

Frisbie commented, "The future brings more choices (for treatment of health problems), and we are always left wondering which to use. That is the impetus of this study."

The molecule interleukin-1 is one of the major mediators of joint disease, explained Frisbie; the increased levels of interleukin-1 receptor antagonist (IL-1Ra) in IRAP products treat arthritis by blocking interleukin-1's destructive effects. Both IRAP products involve pulling blood from a horse, then incubating it for 24 hours with glass beads that stimulate production of anti-inflammatory proteins including IL-1Ra. Finally, a veterinarian injects the conditioned serum back into the arthritic joint to reduce inflammation and help heal the joint.

For the current study, Frisbie and colleagues examined the composition of serum prepared using both IRAP 1 and IRAP II products. They found that both products yielded increased levels of IL-1Ra and insulinlike growth factor as compared with untreated serum, but IRAP II yielded more than twice the amount of IL-1Ra, which theoretically would magnify its beneficial effects. Also, using IRAP II resulted in lower production of tumor necrosis factor-α (alpha, another pro-inflammatory cytokine, or mediator of inflammation) than when IRAP I was used.

"ACS (IRAP) II, with an increased growth factor and anti-inflammatory cytokine profile and no significant increase in pro-inflammatory cytokines, showed a superior profile compared with ACS I," Frisbie summarized.