In the context of TB,infected migratory DCs are poor antigen-presenting cells,21 which suggests that infected cells have a mechanism to transfer antigen touninfected cells so that uninfected cells could prime CD4+ T cells.In vivo studies demonstrated that migratory DCs mustcollaborate with one or more resident DCs to successfully prime CD4+ Tcells.22 The gene discussed is CD4; the disease is tuberculosis.