Interestingly, following D22 (ICP22 null) infection, cytokine levels increased to equal those following KOS infection for the following infiltrates: CD8+IL-2+ (18.3% vs. 16.9%, Fig. 6A), CD8+perforin+ (0.6% vs. 0.6%, Fig. 6G), and CD8+CD25− (5.4% vs. 2.7%, Fig. 6I). This evidence concerns the gene PRF1 and infection.