RESUMO
During aging an increased number of CD16+ lymphocytes and an impaired NK cell function have been demonstrated both in fresh and cloned NK cells obtained from the peripheral blood of elderly subjects. Recently, two novel surface molecules have been identified by GL183 and EB6 monoclonal antibodies on subsets of resting or activated NK cells. The expression of GL183 and/or EB6 identifies four distinct phenotypically stable NK subsets: GL183+EB6+, GL183-EB6-, GL183+EB6-, GL183-EB6+. Our study aimed at analyzing the distribution of GL183 and EB6 NK cell subsets in a group of elderly people and at establishing whether a different distribution of these NK lymphocyte subpopulations is related to the altered cytolytic activity found in the elderly. A broad individual variability in the percentages of CD16+GL183+ or CD16+EB6+ cells was observed. Nonetheless, the mean percentage of GL183+ cells in the elderly group showed a significant increase. The cytolytic activity of GL183+ and EB6+ sorted subsets showed a decrease that was almost equally distributed between the two subpopulations. Given the hypothesis of the ability of NK cells to discriminate between self and non self, the decreased cytolytic activity of GL183+ and EB6+ subsets could be related to a generally decreased ability of aging NK cells to recognize specific target cells.
