Functional integrity of the CD28 co-stimulatory pathway in T lymphocytes from elderly subjects

Introduction: the antigen CD28, expressed in most T cells, has co-stimulato ry properties and plays a pivotal role in clonal T cell anergy mechanisms. Methods: we have compared proliferative T cell responses after anti-CD3 or in phorbol myristate acetate activation with concomitant CD28 signal in per ipheral blood mononuclear cells from healthy donors aged over 65 [elderly d onors; ED] and young healthy donors (YD; mean age 30 +/- 2.7 years). Results: no proliferative responses were observed in ED and YD with anti-CD 28 monoclonal antibody alone. These responses both were defective in ED, pa rticularly after anti-CD3 monoclonal antibody stimulus (7604 compared with 12 438 c.p.m. in YD, P = 0.001) and were corrected when anti-CD28 monoclona l antibody was added to the culture (17 216 vs 18 536, not significant). Fu nctional integrity of the CD28 co-stimulatory pathway was demonstrated by a nalysis of CD25 expression, interleukin-2 secretion and interleukin-2 gene expression on T cells from ED and YD. Age-associated phenotypic T cell chan ges were not crucial for an adequate CD28 response, Conclusion: these experiments demonstrate the integrity of the CD28 pathway in elderly people, and suggest that ageing does not affect different T cel l activation pathways equally.