As noted, Ahmed initially found that stem-like PD-1loCD8+ Tex express CXCR5; however, these cells co-express high amounts of Ccr7 transcripts, migrate in response to a CCL19/21 gradient in vitro, and localize to the splenic T cell zone in vivo after Clone 13 infection (47). The gene discussed is CXCR5; the disease is infection.