Persistent parasite infection, including Leishmania major or P. chabaudi, generate recirculating Tcm that do not protect as well as activated Teff or Tem, defined as previously divided CD4+CD62Llo Tem/Teff [9], or distinguished as CD127− Teff and CD127hi CD44hi CD62Llo CD27− Tem [10]. The gene discussed is CD4; the disease is parasitic infectious disease.