Immunoadjuvant activity of icariin that induces Th1-type antibody in mice

The adjuvant effect of icariin from Epimedium koreanum on the immune responses to bovine serum albumin (BSA) in mice was examined. Mice were immunized on days 1 and 22 intraperitoneally (i.p.) with one of the following: an emulsion form of BSA mixed with Incomplete Freund's Adjuvant (BSA/IFA) or with Complete Freund's Adjuvant (BSA/CFA) or BSA plus icariin mixed with IFA (BSA/Icariin/IFA). One week after the booster, polyclonal sera were collected from these animals to determine IgG isotypes specific for BSA in the sera and then spleens of these animals were harvested to evaluate IFN-γ and IL-4 produced in the splenocyte cultures. In order to determine the DTH (delayed type hypersensitivity) response, BSA was administered into the footpads of mice that were immunized as described above and the degree of footpad-swelling was measured. Data from these experiments showed that the icariin combined with BSA (BSA/Icariin/IFA) provoked the most abundant of IgG production in mice and enhanced the Th1-lineage development of IgG2a and IFN-γ productions (p < 0.05), whereas BSA/IFA resulted in a highest ratio of IgG1 to IgG2 and most dominant IL-4 production, indicating a Th2 response. This pattern of immunity was confirmed by the DTH determination revealing that icariin-containing formula caused the highest footpad-swelling followed by BSA/CFA and BSA/IFA, respectively. In addition, hemolytic assay showed that icariin at a dose of 1000 μg/mL caused no hemolysis when compared with a water-treated mouse. All of these data indicate that icariin has the immunoadjuvant effect which may enhance Th1-immune response, suggesting that icariin as an adjuvant would be beneficial in the treatment of Th1-disordered diseases.