Changes in serum levels of cytokines in mice injected with an immunostimulator C3bgp isolated from Cuscuta europea

The effect of C3 binding glycoprotein (C3bgp), isolated from Cuscuta europea seeds on induction of in vivo cytokine synthesis was investigated. Different groups of mice were stimulated with 30 microg C3bgp per mouse, injected intraperitoneally. The quantitative determination of IL-1alpha, IL-2, IL-4, IL-6, IL-10, TNF-alpha and IFN-gamma was performed in mouse sera by ELISA. The quantities of these cytokines were measured at different hours: 1, 2, 3, 4, 5, 6, 7, and 24 h after injection. No significant changes in serum level of IL-2, IL-4 and TNF-alpha in experimental animal groups were found. A little increase of IL-1alpha, moderate elevation of IL-10 and IFN-gamma (5- to 6-fold more) and strong release, more than 10-fold of IL-6 in sera of C3bgp-treated mice were detected. The results obtained from C3bgp stimulated cultures of mouse peritoneal macrophages and mouse splenocytes suggest that C3bgp binds to mouse peritoneal macrophages and induces production mainly of IL-6, followed by IFN-gamma and in a very low degree of IL-1alpha and IL-10. Based on the results presented, we conclude that the increased level of IL-6 was the basic after injection of C3bgp and that the mouse macrophages were the major cell targets for the C3bgp effect.