Early activation of gamma delta T lymphocytes in the elderly

T cell function is altered in vivo and in vitro in elderly compared with yo ung subjects, and this alteration is believed to contribute to morbidity an d mortality in man due to the greater incidence of infection, as well as au toimmunity and cancer in elderly. The majority of T cells express TCR alpha beta whereas TCR gamma delta is expressed on a minority of T cells. Moreov er, it is known that gamma delta T lymphocytes display major histocompatibi lity complex (MHC)- unrestricted cytotoxicity that is reminiscent of natura l killer (NK) activity. In view of earlier findings on both T cells and NK cells in the elderly, we hypothesised a different behaviour of gamma delta T lymphocytes from old subjects when compared with gamma delta T lymphocyte s obtained from young people. Therefore, to gain further insight into mecha nisms of immunosenescence in this little-studied population, we studied imm unofluorescence analysis gamma delta T cells from the elderly. Our prelimin ary results show that the percentage of blood gamma delta T cells in lympho cytes from old subjects is decreased when compared with the young. Interest ingly, these cells are more activated in the elderly than in young subjects ; expression of CD69, an early activation marker. is increased in gamma del ta T lymphocytes from old subjects after three hours of in vitro culture bo th with and without lipopolysaccharide stimulation. Thus, our findings, whi ch need confirmation, strongly suggest that, in humans, gamma delta T cells are early responders when compared with alpha beta T cells. They may act a s 'first aid' cells to replace the described deficit of the specific and as pecific immunity in elderly. In this view, the proinflammatory status, obse rvable in the elderly, renders them ready to be stimulated by exogenous age nts. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.