Modulation of natural killer cell functional activity in athymic mice by beta-carotene, oestrone and their association.

In athymic mice, Natural Killer (NK) cells influence the take rate and growth of human malignant tissue xenografts. To confirm preliminary results, comparative experiments were conducted to study the effects of beta-carotene, oestrone and their association on the cytolysis mediated by spleen NK cells from athymic mice receiving these different treatments. Target cells consisted of YAC-1 malignant cells. With a 65% increase of cytolysis (ratio effector/target 50:1), beta-carotene induced a significant activation of NK cells (p < 0.002). This effect could be attributed to its antioxidant properties and confirmed by a moderate increase in erythrocyte glutathione peroxidase activity. On the contrary, oestrone resulted in a significant decrease of cytolysis (p < 0.001). In this case, the prooxidant properties of oestrone could explain its effect on NK cells and agree with the increase of intracellular reduced glutathione level observed. When mice received the combination beta-carotene-oestrone, their opposite effects on NK cell activity were counterbalanced, leading to a moderate change of cytolysis.