Background：L-10 was originally described as Cytokine Synthesis Inhibitory Factor （CSIF） by virtue of its ability to inhibit cytokine production by Th1 clones. IL-10 shares over 80％ sequence homology with the Epstein-Barr virus protein BCRFI. IL-10 inhibits IFN-gamma, TNF-b, and IL-2 production by Th1 clones; inhibits macrophage-mediated IL-1, IL-6, and TNF-a synthesis; suppresses the delayed type hypersensitivity response; stimulates Th2 cell response （which results in elevated antibody production）; and promotes mast cell proliferation in combination with IL-4.
