AbstractDuring the last few years, several observations outline that the impaired T lymphocyte proliferative capacity in the elderly is due to a reduced interleukin 2 (IL-2) release. to further investigate the activation process during lectin stimulation, aged peripheral blood mononuclear cells (PBMC) were stimulated with phytohemagglutinin (PHA) and assessed for CD25 (IL-2 receptor) and CD71 (transferrin receptor) expression at different intervals of time. Our results provided evidence for a significant decline of both structure induction, above all in the later phase of culture. Indomethacin (INDO) treatment gave rise to an enhancement of CD71 antigen expression only, while prostaglandin E2 (PGE2) supplementation to culture media further decreased either CD25 or CD71 receptor induction. Interferon (IFN)-αand IFN-γtreatment failed to modulate the frequency of CD25+and/or CD71+cells. Finally, the expression of CD71 receptor was increased by deferoxamine supplementation, this suggesting a partial involvement of iron overload in the depressed function.Although further studies are required to evaluate at a molecular level the decreased antigen expression, these findings indicate that several mechanisms are involved in the elderly-related decline of T lymphocyte activation structures during lectin stimulation.