After establishing the early proliferation of antigen-specific CD4+ T cell populations due to LdCen−/−2W immunization either in the absence or presence of previous asymptomatic infection, we wanted to determine whether the proliferated cells start to acquire memory characteristics by examining the expression of memory markers on the surface (CD62L, CCR7, and IL7R, characteristic of central memory T cells). The gene discussed is CD4; the disease is infection.