To study this, we generated Cd4cre × Embfl/fl mice and used several CD4+ T cell–dependent models to phenotype these mice, including lung TRM cell generation by mucosal vaccination, the lung homing property of lung TRM cells, the experimental autoimmune encephalomyelitis (EAE) model, Pneumocystis infection, as well as generation of CD8+ T cell memory after influenza infection. Here, CD4 is linked to Pneumocystis infectious disease.