Improvement of natural killer cell activity by in vitro active lipids (AL 721) administration in old mice

Results of several experiments have given rise to the hypothesis that the decline of the immunocompetence with aging is at least in part related to alterations of the lipid membrane composition and, consequently, to a decrease in membrane fluidity. The age-dependent decline of mitogen responsiveness can, in fact, be reversed by a special lipid mixture designated as active lipids (AL 721), which acts by means of its fluidizing action on the plasma membrane. The purpose of this study was to examine the possibility of raising the low endogenous levels of Natural Killer (NK) activity by in vitro AL administration in old mice. When spleen cells from old mice were incubated in vitro with AL, a significant increase in cytotoxic activity was obtained over control cultures, without reaching, however, the levels observed in young mice. In spleen cells from young mice, the AL administration causes a slight augment of NK basal activity. These results suggest that cell membrane fluidity plays an important role in the efficiency of NK cells, giving support to the hypothesis that a rectification of rigidified cell membranes may represent a valuable approach to restore proper physiological functions in old age.