CD4 and hepatitis A virus infection: Mechanistically, the 9,12-octadecadienoic acid can modulate the hepatic immune microenvironment in the hepatitis mouse models [27], stimulate the expression of neutrophils and macrophages [27, 28], up-regulate the level of inflammatory factors [29], induce high expression of carnitine palmitoyltransferase leading to increased apoptosis of CD4+ T cells [30], and ultimately contribution to the HCC progression [31].