CD8A and viral infectious disease: Of note, progeny CD8+ T cells were comprised of both, GFP+ (CX3CR1+) and GFPneg (CX3CR1neg) T cells (Fig. 3f), indicating that CX3CR1-expressing CD8+ T cells can arise from GFPneg (CX3CR1neg) memory CD8+ T cells during recall responses after viral infection.