Oral beta-carotene can increase the number of OKT4+ cells in human blood.

Oral doses of beta-carotene (180 mg/day) given for 2 wk to normal human volunteers significantly increased the frequency of OKT4+ (helper/inducer T cells) after 7 days and of OKT3+ (all T cells) after 14 days. The frequency of OKT8+ cells was unaffected, as compared to untreated controls. Plasma levels of beta-carotene were markedly elevated throughout the study. Plasma levels of vitamin A were slightly (but significantly) elevated on days 7 and 14. No toxicity was observed. Oral beta-carotene treatment may be a clinically effective means of enhancing T4+ lymphocytes.