In this study, rFg-CaBP4 protein demonstrated a significant inhibition of the Th2 type immune response, as indicated by the reduction of the IL-10 cytokine level in host monocytes, and exerted a suppressive effect on the differentiation of regulatory T cells, which may be an immune modulatory role of Fg-CaBP4 against fascioliasis. The gene discussed is IL10; the disease is fascioliasis.