CD4 and chronic hepatitis B virus infection: Our previous study compared the acetylation modification state of histone H3K9 of peripheral blood CD4 + T cells in the whole genome promoter region under different disease states of chronic hepatitis B and found that H3K9 acetylation (H3K9Ac) modification regulation exists in 2 sequence regions of TLR9, suggesting that H3K9 acetylation modification of TLR9 also plays an essential role in the occurrence and development of chronic hepatitis B.[22]