Beta-carotene enhances natural killer cell activity in athymic mice.

To study the effects of beta-carotene on Natural Killer (NK) cells, we chose athymic mice whose spleens have a higher percentage of NK cells than conventional mice. Preliminary studies conducted with beta-carotene given intraperitoneally to athymic mice xenografted with a small-cell lung carcinoma resulted in a slight but significant antiproliferative effect (unpublished observations). We speculated that such an activity of beta-carotene was related to its immunostimulating properties. NK cell activity in ungrafted athymic mice as influenced by beta-carotene was studied. Mice received beta-carotene intraperitoneally. Splenic NK cells were labelled with monoclonal antibody and numeration was completed by measurement of their functional activity against YAC-1 malignant cells with a 51Cr release assay. In addition, splenic lymphocytes were evaluated for their reduced glutathione (GSH) content. There was a non-significant increase in the number of NK cells in the spleen, however their killing capacity was significantly (p < 0.01) enhanced after beta-carotene treatment. Also the GSH content of splenic lymphocytes was significantly higher in beta-carotene treated mice. Comparison of the average body weights of treated animals and of their respective controls showed that treatment had no adverse effects.