Immunohistochemical (IHC) staining of liver tissues from patients with acute liver failure (ALF) caused by HEV showed that the levels of CD3, CD8 (cytotoxic T cells), Granzyme B (granzyme B: Activated cytotoxic T cells and NK cell markers), CD56 (natural killer cells), CD4 (helper T cells), and CD8/CD3 and CD4/CD3 ratios were higher than those in normal liver tissue. This evidence concerns the gene CD4 and acute liver failure.