Abstract: Objective To investigate the effects of MmMIF and PyMIF in vitro on the TLR4 expression, the Surface Molecules Expression Level and IL-12, TGF-β1 production of Spleen DC. Methods Recombinant plasmids were transformed into Escherichia coli BL21 (DE3), and expression of the recombinant PyMIF-His and MuMIF-His was induced by the addition of 0.5 mM IPTG to the bacterial culture and incubated for 4 h at 37°C. The fusion protein was purified using Nickel-affinity chromatography column and endotoxin was removed from the recombinant protein by Sep-Pak C8 column. CD4+DC /CD8+DC were collected from Spleen by CD4+DC /CD8+DC Isolation Kit. After 24 h of treatment with LPS, MmMIF or PyMIF, the TLR4 expression and the surface molecules expression level of CD4+DC and CD8+DC were determined by flow cytometry. IL-12, TGF-β1 production were detected by ELISA. Results The surface molecules expression level of DC didn't change. PyMIF treatment of CD8+DC down-regulated surface expression of TLR4 and IL-12 (from 433±48 pg/mL to 373±30 pg/mL, P<0.05) secretion decreased significantly after LPS stimulation. PyMIF treatment of CD8+DC increased TGF-β1 (from 136±4 pg/mL to 182±7 pg/mL, P<0.05) significantly. Conclusion PyMIF treatment exerts no effects on maturation of Spleen DC. CD8+DC modified by PyMIF down-regulated IL-12 significantly after LPS stimulation and immature CD8+DC modified by PyMIF up-regulated TGF-β1 secretion, thereby regulating the host immune response and conducive to P. yoelii survival.

Key words: PyMIF, Spleen CD8+DC, Spleen CD4+DC, IL-12, transforming growth factor-beta1