The laid eggs of paired worms (4 and 6 weeks post infection for S. japonicum and S. mansoni, respectively) act as antigens that stimulate the host to generate a strong Th2 response, with elevated production of the Th2-type cytokines IL-4, IL-5, IL-9, and IL-13, under the control of regulatory T-cells (Tregs) (Wynn et al., 2004). The gene discussed is IL13; the disease is infection.