CD4 and cytomegalovirus infection: The recent demonstration that T-bet induction on CD4+ T-cells in response to CMV stimulation, which correlated with proliferation and effector multifunction, allows us to differentiate lung transplant recipients mismatched for CMV that control CMV replication from those with early relapse [34] supports the relevance of this transcription factor in the generation and maintenance of CD4+ effector cells able to establish effective immune control during the early stages of CMV infection.