Selective Th1 up-regulating activity of Withania somnifera aqueous extract in an experimental system using flow cytometry

Withania somnifera (Ashwagandha) is reported to be immunoprotective and immunoadjuvant. We studied its roots aqueous extract on T helper (Th) immunity using flow cytometry. This extract was standardized with six withanolides as marker compounds using HPLC. Once daily dose ranging from 25 to 400 mg/kg/p.o. was used to study effect on Th1: IFN-gamma, IL-2 and Th2: IL-4 cytokine modulation. We also studied effect on CD4 and CD8 in normal and immunesuppressed mice. The results indicate that extract at 100 mg/kg resulted significant selective up-regulation of Th1 response. Treatment with extract showed significant increase in CD4 and CD8 counts as compared to control and cyclopsorin A, with a faster recovery of CD4+ T cells in immunesuppressed animals. Under immunesuppressed conditions, potentiation of cellular and humoral immune responses of extract was comparable to levamisole. This study indicates the selective Th1 up-regulating effect of extract and suggests its use for selective Th1/Th2 modulation. © 2006 Elsevier Ireland Ltd. All rights reserved.