Further studies using this healed CL animal models revealed that the drivers of protection including the presence of effector CD4 T cell populations that secrete IFN-γ almost instantaneously following challenge infection, and that these Ly6C+CD4+ effector T cell populations are indefinitely maintained by the residual parasites following healing (Figure 1) (Peters et al., 2014; Hohman and Peters, 2019). The gene discussed is CD4; the disease is infection.