Proliferative responses of blood mononuclear cells (BMNC) in a cohort of elderly humans: Role of lymphocyte phenotype and cytokine production

Age-related impaired T cell function is associated with increased mortality risk. The purpose of the present study was therefore to identify factors associated with the age-related decreased phytohaemagglutinin (PHA)- induced proliferative response of lymphocytes in a cohort of 174 81-year-old humans and in 91 young controls. Decreased proliferation was associated with a reduced number of true naive CD4⁺ cells (CD62L⁺CD45RO^-). Furthermore, a low IL-2-stimulated proliferation was correlated with a decreased PHA response in the elderly cohort, whereas reciprocal interactions of IL- 10- and IL-2-producing cells were of importance in both elderly and young subjects. Accordingly, a minimum of true naive CD4⁺ cells was required for a normal proliferative response to PHA, perhaps by providing sufficient IL-2 which is critical for growth of naive as well as memory cells.