To determine if this difference could be due to increased IRF4 expression in T1 versus T2 EBV-infected cluster 9 cells, we compared the levels of IRF4 expression in T1 versus T2 Cluster 9 cells (Fig 18B). Importantly, T1 cells in cluster 9 clearly expressed more IRF4 than T2 LCLs in cluster 9, strongly suggesting that persistent IRF4 expression in T1 cluster 9 cells contributes to their decreased ability to enter fully lytic infection. This evidence concerns the gene IRF4 and infection.