CD4 and infection: Furthermore, previous studies showed that, in mice immunized with SmCB1 and subsequently infected with cercariae, SmCB1 elicited IFN-γ and IL-17 production from cells in the lymph node draining the site of infection 4 days after challenge [36], suggesting that the protease may have broad CD4+ T cell-priming activity that extends beyond TH2 cell induction.