THE ROLE OF VITAMIN-A IN NATURAL-KILLER-CELL CYTOTOXICITY, NUMBER ANDACTIVATION IN THE RAT

The cause of low natural killer (NK) cell activity in vitamin-A-defici ent rats was investigated in the current study. Cytotoxicity correlate d with the percentage of NK cells (3.2.3-positive cells) in peripheral blood mononuclear cells (PBMC; r = 0.85) and spleen (r = 0.70). Lytic activity per NK cell did not differ between vitamin-A-deficient rats and controls in PBMC, whereas it did in spleen. Vitamin A deficiency d id not impair the ability to produce interferon (IFN), increase lytic efficiency and expand the NK cell pool upon poly(I:C) stimulation in v ivo. Nor was the in vitro activation by IFN-alpha/beta or interleukin- 2 affected. Thus, vitamin A is essential for maintaining basal NK cell number and activity, but not for NK cell activation.