CX3CR1 and infection: In addition, the Mtb-specific CD4+ T cell population in Mtb-infected CCR2ΔMHCII mice contained the same number of CXCR6+ Ly-6C– Th1 resident memory and terminally differentiated CX3CR1+ Th1 cells, and only marginally fewer CXCR6+ Ly-6C+ Th1 effector memory cells [10,47–49] than CCR2WT mice at 6 weeks post-infection (Fig 3F).