CCR5 and infection: Thus, persistent HIV/SIV replication and infection and chronic systemic immune activation (49) accompanied with elevated proinflammatory cytokine responses, and persistent antigen stimulation, drives TFH precursor activation, migration to and infection within the T-cell zones, and subsequent migration into the GC where GC TFH fully mature, lose CCR5 expression, and persist as productively and latently infected cellular reservoirs for HIV/SIV infection.