Autologous-Conditioned Serum (ACS or IRAP™ II) Therapy

Radiograph of a horse hoof with arthritis of the pastern joint

What is ACS for horses?

ACS is a blood product containing concentrated amounts of an anti-inflammatory protein called interleukin-1 receptor antagonist protein (IRAPTM II). It is most commonly used to treat the early stages of osteoarthritis.

What does ACS therapy do for lameness in horses?

The interleukin-1 receptor antagonist protein is injected into the affected joint, slowing the inflammatory process that leads to and perpetuates cartilage damage and osteoarthritis. Unlike repeated injection of cortisone-like steroids, IRAPTM II may be used repeatedly without detrimental effects to the cartilage. If used early in joint disease, IRAPTM II may prevent early progression and development of osteoarthritis which may prolong the performance years of your horse and prevent early retirement, as well as decrease the need for continued veterinary treatment and costly therapies.

ACS Therapy at UF

Collecting IRAP Serum at the UF Large Animal Hospital

Separating serum after incubating

Two forms of IRAP/ACS are available at UF. IRAPTM II is made by incubating blood from the patient for 24 hours. The horse remains at the hospital overnight and the first treatment can be performed the following day. Additional samples can be shipped to the primary care veterinarian for follow-up treatments.

Alternatively, ACS can be produced at the same time as stem cell expansion or PRP. These therapies can then be used in combination for reduced overall cost to the client.

The affected joint is usually treated every 7-10 days for three or more treatments. The amount of IRAPTM II injected depends on the size and location of the joint. Rest is typically recommended following each injection.

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