CD4 and tuberculosis: Earlier and greater-magnitude expansion of Vγ2Vδ2 T cells during Mtb infection appears to create a proof-of-concept setting in which to examine immune function of Mtb-specific Vγ2Vδ2 T effector cells in primates, as rapid clonal expansion and pulmonary trafficking of Mtb-specific CD4+/CD8+ T cells have been interpreted as important immune events in immunity against TB in macaques [40].