CD4 and infection: These multifunctional memory CD4 T‐cells are found following vaccination or infection in animal models and in humans.24, 25, 26, 27, 28, 29 In infection models of Leishmania major and Mycobacterium tuberculosis, multifunctional CD4 T‐cells provide the most effective immune protection, and in humans they correlate with successful recovery from infection with Japanese encephalitis virus.25, 27, 29