The effect of aging on immune responses

Horses older than 20 years of age constitute approximately 15% of the equine population, and many remain actively involved in equestrian sports and reproductive capacities as stallions and broodmares [1]. Nevertheless, advancing age in horses, as with other species, is eventually associated with a decline in body condition and muscle tone as well as an increase in susceptibility to infections [2-4]. This increased susceptibility to infectious diseases is caused by an overall decline in immune function that results from alterations of many different elements of the immune system. Although these changes have been extensively documented in human beings and mouse models, little research has been done on the equine system.