The effect of aging on T cell responses in the horse

Horses greater than 20 years of age exhibit alterations in their immune res ponses similar to those observed in other aged individuals. The purpose of this study was to characterize immunosenescence in a population of aged pon ies. The peripheral blood mononuclear cells (PBMC) from aged ponies exhibit ed a decreased proliferative response to various mitogens that was not over come by the addition of interleukin 2 (IL-2) to the cultures. No difference in overall expression of the IL-2 receptor was seen between young and aged ponies, though CD8(+) cells from aged ponies exhibited increased levels of IL-2 receptor expression. The kinetics of the response to both mitogen and IL-2 did not appear to be affected in the aged PBMCs. These results indica te that the age-related decrease in the proliferative response to mitogens is not due to a failure to produce or respond to IL-2 but probably involves some other process. (C) 2001 Elsevier Science Ltd. All rights reserved.