The results showed that the expressions of TNF-α, IL-12, IL-5, IL-10 and GM-CSF in serum increased from five weeks post-infection and to peak levels at week 6 post-infection; however, as typical type 1 cytokines, the levels of IL-2 and IFN-γ in serum did not change during the key period. Here, IL2 is linked to infection.