TGFB1 and infection: As shown in Figure 4C, during the whole experimental infection, the concentration of TGF-β1 in the serum at 8 wk p.i. and 16 wk p.i. was significantly higher than that of in the control mice (P < 0.05), and the level of TGF-β1 were increased from 4 wk p.i. to 16 wk p.i during the development of infection.