RT Journal Article SR Electronic T1 Anti-allergic Psidium guajava Extracts Exert an Antitumor Effect by Inhibition of T Regulatory Cells and Resultant Augmentation of Th1 Cells JF Anticancer Research JO Anticancer Res FD International Institute of Anticancer Research SP 3763 OP 3770 VO 25 IS 6A A1 NAOHIRO SEO A1 TAISUKE ITO A1 NAILI WANG A1 XINSHENG YAO A1 YOSHIKI TOKURA A1 FUKUMI FURUKAWA A1 MASAHIRO TAKIGAWA A1 SUSUMU KITANAKA YR 2005 UL http://ar.iiarjournals.org/content/25/6A/3763.abstract AB Th1 polarization is one of the mechanisms underlying the therapeutic effects of herbal medicine. The action of anti-allergic agents from Psidium guajava (P. guajava) on T cell immunity in mice was investigated. The addition of P. guajava extracts blocked IL-10-mediated, in vitro induction of T regulatory (Tr) cells from CD4+ splenocytes of C57BL/6 mice, whereas the extracts exerted only a weak or no effect on the development of Th1 and Th2 cells. Accordingly, Tr cells were not induced from splenocytes of mice administered orally with the extracts. Furthermore, P. guajava extracts shifted the Th1/Th2 balance to a Th1 dominant status by directly attenuating Tr cell activity. In a study of tumor immunity, mice pretreated with the extracts exhibited retarded growth of s.c. inoculated B16 melanoma cells. These findings suggest that P. guajava extracts are efficacious for the prevention of tumor development by depressing Tr cells and subsequently shifting to Th1 cells. Copyright© 2005 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved