Early activation of gammadelta T lymphocytes in the elderly

T cell function is altered in vivo and in vitro in elderly compared with young subjects, and this alteration is believed to contribute to morbidity and mortality in man due to the greater incidence of infection, as well as autoimmunity and cancer in elderly. The majority of T cells express TCRalphabeta whereas TCRgammadelta is expressed on a minority of T cells. Moreover, it is known that gammadelta T lymphocytes display major histocompatibility complex (MHC)- unrestricted cytotoxicity that is reminiscent of natural killer (NK) activity. In view of earlier findings on both T cells and NK cells in the elderly, we hypothesised a different behaviour of gammadelta T lymphocytes from old subjects when compared with gammadelta T lymphocytes obtained from young people. Therefore, to gain further insight into mechanisms of immunosenescence in this little-studied population, we studied immunofluorescence analysis gammadelta T cells from the elderly. Our preliminary results show that the percentage of blood gammadelta T cells in lymphocytes from old subjects is decreased when compared with the young. Interestingly, these cells are more activated in the elderly than in young subjects; expression of CD69, an early activation marker, is increased in gammadelta T lymphocytes from old subjects after three hours of in vitro culture both with and without lipopolysaccharide stimulation. Thus, our findings, which need confirmation, strongly suggest that, in humans, gammadelta T cells are early responders when compared with alphabeta T cells. They may act as 'first aid' cells to replace the described deficit of the specific and aspecific immunity in elderly. In this view, the proinflammatory status, observable in the elderly, renders them ready to be stimulated by exogenous agents.