EFFECT OF LONG-TERM ADMINISTRATION OF BETA-CAROTENE ON LYMPHOCYTE SUBSETS IN HUMANS

To examine whether or not beta-carotene alters immune indexes, we perf ormed a single-blind trial in healthy male nonsmokers. Lymphocyte subs ets were assessed by double labeling with monoclonal antibodies before and after 44 wk of administration of either beta-carotene (60 mg/d; n = 10) or placebo (n = 10). In addition, we measured the beta-carotene concentrations in plasma, mononuclear cells (MNC), platelets, and red blood cells (RBCs), as well as the plasma alpha-tocopherol concentrat ion. An increase of plasma and MNC beta-carotene concentrations to fou r and three times the baseline value was noted after 2 and 4 wk, respe ctively. The CD4-CD8 ratio increased after 9 mo of beta-carotene admin istration whereas natural killer cells, virgin T cells, memory T cells , and cytotoxic T cells remained unaltered throughout the study. No si de effects or toxicities were detected by a questionnaire survey and r outine laboratory tests.