Effect of long-term administration of (beta)-carotene on lymphocyte subsets in humans

To examine whether or not beta-carotene alters immune indexes, researchers performed a single-blind trial in healthy male nonsmokers. Lymphocyte subsets were assessed by double labeling with monoclonal antibodies. The CD4-CD8 ratio increased after nine months of beta-carotene administration, whereas natural killer cells, virgin T cells, memory T cells and cytotoxic T cells remained unaltered throughout the study.