Cell mediated immunity changes in ageing, relative importance of cell subpopulation switches and of nutritional factors.

Decreased T-cell functions with ageing have been extensively described. This review focuses on recent data on changes in T-cell subpopulations related to ageing and their consequences on T-cell proliferation. Increase of immature T cells CD2+ CD3- is an ageing phenomenon related to T-cell declining proliferation. Recently it was shown that increase of immature T cells was due to an increase in different subtypes of the CD2+ CD3- population, double-negative CD2+ CD4- CD8- and double-positive CD2+ CD4+ CD8+ subpopulations, the former being associated with nutritional deficit, the latter with associated diseases. Other authors have focused on decreases of native T cells with parallel increase of memory T cells; such a switch is also relevant to declining T-cell proliferation. This review focuses on two major factors which influence immune ageing; nutritional parameters and antigen exposure.