Neubauer et al. (2000b) for the first time showed the expression of CD31 on LSECs and found no observable difference in CD31 expression under normal conditions and carbon tetrachloride-induced (CCl4) liver fibrosis. However, another study by the same authors demonstrated a constitutive expression of CD31 on LSECs, whereas, a decrease of CD31 was observed after CCl4 administration mediated by TNF-α in vitro. They hypothesized that reduced CD31 expression might aid in more desirable mononuclear cell transmigration (Neubauer et al., 2000a). The gene discussed is PECAM1; the disease is Hepatic fibrosis.