Phenotypic expression of natural killer cell associated membrane antigens and cytolytic function of peripheral blood cells from different aged humans.

The function and phenotypes of peripheral blood NK cells from different aged adults were examined using a 4 hr 51Cr release NK assay and laser flow cytometry utilizing the Leu-7 and Leu-11 monoclonal antibodies. It was found that there was no difference between aged and young adults in the expression of Leu-7+, Leu-11+, Leu-7-11+ or Leu-7+11+ cells. A significant decrease, however, was seen in both percent representation and absolute number of Leu-7+11- cells in older subjects. When examined by age and gender, women aged 17-59 yr had a significantly lower percent representation and absolute number of Leu-11+, Leu-7-11+ and Leu-7+11+ cells and baseline NK activity than did men of similar age. No differences were seen between men and women aged 60-84 yr. No differences were seen in the degree of augmentation by interleukin-2 of NK function in any group. Our data indicate that NK function is correlated with cells bearing the Leu-11 surface antigen and that the gender of the cell donor is a significant factor in the representation of NK cells and function in persons under 60 yr of age. Studies on age differences in NK number and function must therefore take into account the percent of women in the populations studied.