Increased expression of co-stimulatory molecules and enhancement of the IgG response in rats orally administered with a polyherbal formulation

BACKGROUND: Link Samahan® (LS) is a standardized modern formulation of a polyherbal preparation used in the indigenous system of medicine in Sri Lanka. OBJECTIVE: Evaluation of the immunostimulatory activity of LS and the molecular mechanisms that modulate the humoral immune response. MATERIAL AND METHODS: Immunostimulatory activity of LS was tested in rats following oral administration on days 1-5 and 15-19 and immunization with bovine serum albumin (BSA) on day 1 and 15. Anti-BSA IgM and IgG response in rats treated with LS, water and sugar (as controls) were compared on days 0-35, using ELISA. The expression of co-stimulatory molecules on lymphocytes was assessed on days 0-8 and days 14-22 using RT-qPCR. RESULTS: IgM and IgG levels of LS-treated rats were increased significantly by day 7 and 21 respectively compared to controls (p < 0.05). IgG response of LS-treated group reached a higher magnitude compared to its IgM response. Gene expression of CD28 and CD40L on T cells (4.9-5.1 fold) and CD80, CD86 and CD40 on APCs (2.4-3.1 fold) were induced significantly by day 2 compared to their expression on day 0 (p < 0.05). The expression levels of CD28 and CD40L on day 2-4 and 16-18 were similar while the expression of CD80, CD86 and CD40 on day 16-18 was higher (3.7-5.1 folds) compared to their levels on day 2-4 (2.4-3.2). CONCLUSIONS: These findings support an adjuvant effect of LS contributing to its immunostimulatory activity and increased expression of co-stimulatory molecules that contribute to boosting immune response.