Impairment of gamma/delta T lymphocytes in elderly: implications for immuno senescence

Gamma/delta T lymphocytes cells recognize the antigen in a non-classical way and are considered the third branch of the immune system devoted to defend the integrity of the body. Ageing is characterized by an impairment of the main way of protection (the adaptive branch) but, successfully aged people show compensatory mechanisms of defense such as proneness to inflammation. Moreover, very old subjects show an increased number of NK cells. We have previously demonstrated that gammadeltaT lymphocytes are reduced in elderly. In the present paper we have studied some characteristics of these cells to evaluate the possibility that these cells might balance the decreased action of the adaptive branch in successfully aged people. Cytofluorimetric analysis of cells collected from young, old and centenarian subjects has been used to evaluate the ability of these cells to expand in vitro. Here we demonstrate that gammadeltaT cells are impaired in the ability to proliferate to different stimuli such as isopentenyl pyrophoshate, that select gammadeltaT lymphocytes bearing delta2 chain, other than to phytohemagglutinin and anti-CD3 that are polyclonal activators. Moreover, we demonstrate that gammadeltaT cells in aged and centenarians show an enhanced sensitivity to undergo apoptosis induced both by alpha-Fas and TNF-alpha. All together these data suggest that gammadeltaT lymphocytes are impaired in elderly and suggest that the reduced ability to proliferate and the reduced number of circulating gammadeltaT lymphocytes is due to the proneness to apoptosis. Finally on the basis of these data. we conclude that gammadeltaT lymphocytes, do not participate in the remodeling of the immune system due to the reduction of classical T cell response and replacement by NK cells in elderly. (C) 2004 Elsevier Inc. All rights reserved.