Basic Research
Copyright ©The Author(s) 2005. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 7, 2005; 11(37): 5777-5781
Published online Oct 7, 2005. doi: 10.3748/wjg.v11.i37.5777
Consumption of purple sweet potato leaves modulates human immune response: T-lymphocyte functions, lytic activity of natural killer cell and antibody production
Chiao-Ming Chen, Sing-Chung Li, Ya-Ling Lin, Ching-Yun Hsu, Ming-Jer Shieh, Jen-Fang Liu
Chiao-Ming Chen, Graduate Institute of Pharmacy, Graduate Institute of Nutrition and Health Sciences, Taipei Medical University; Department of Dietetics, Taipei Medical University Hospital, Taipei, Taiwan, China
Sing-Chung Li, Ya-Ling Lin, Ming-Jer Shieh, Jen-Fang Liu, School of Nutrition and Health Sciences, Taipei Medical University, Taipei, Taiwan, China
Ching-Yun Hsu, Chang-Gung Institute of Technology, Taoyuan, Taiwan; Graduate Institute of Pharmacy, Taipei Medical University, Taipei, Taiwan, China
Author contributions: All authors contributed equally to the work.
Supported by the Grant From the Taipei Medical University, No. TMU91-Y05-A110, TMU92-AE1-B33
Correspondence to: Dr. Jen-Fang Liu, School of Nutrition and Health Sciences, Taipei Medical University, 250 Wu-Shing Street, Taipei 110, Taiwan, China.
Telephone: +886-2-27361661-6551 Fax: +886-2-27373112
Received: December 12, 2004
Revised: January 2, 2005
Accepted: January 5, 2005
Published online: October 7, 2005

AIM: To study the immunological effects of physiological doses of purple sweet potato leaves (PSPL).

METHODS: The randomized crossover study (two periods, each lasting for 2 wk) involved 16 healthy non-smoking adults of normal weight. The 6-wk study consisted of a run-in (wk 1) PSPL diet (daily consumption of 200 g PSPL) or a control diet (low polyphenols, with the amount of carotenoids adjusted to the same level as that of PSPL) (wk 2-3), washout diet (wk 4), and switched diet (wk 5-6). Fasting blood was collected weekly in the morning. T-lymphocyte function was assessed via the proliferation and secretion of immunoreactive cytokines. Salivary IgA secretion and the specific cytotoxic activities of cytotoxic T lymphocytes and natural killer (NK) cells were determined.

RESULTS: The plasma β-carotene level increased with time in both groups, while the plasma polyphenol level decreased in the control group, and no significant difference was detected between the two groups. Although plasma polyphenol levels did not significantly increase in the PSPL group at the end of the study, they were significantly elevated in urine. PSPL consumption produced a significant increase in proliferation responsiveness of peripheral blood mononuclear cells (PBMC) and their secretion of immunoreactive IL-2 and IL-4. As well, lytic activity in NK cells was elevated in a time-dependent fashion. Salivary IgA secretion significantly decreased in control group after 2 wk, and returned to baseline following dietary switch to PSPL.

CONCLUSION: Consumption of PSPL modulates various immune functions including increased proliferation responsiveness of PBMC, secretion of cytokines IL-2 and IL-4, and the lytic activity of NK cells. The responsible determinants of PSPL remain to be elucidated, as does the biological significance of the present observations.

Keywords: Purple sweet potato leaves, Polyphenol, Immune function