Adhesion molecules play an important role in inflammation by determining the ability of cells to adhere to one another, or to the extracellular matrix. The expression patterns of adhesion molecules on cell surfaces have a major influence on how immune cells are recruited to different tissues. One hypothesis about the liver disease of primary sclerosing cholangitis (PSC) is that long-lived mucosal T cells are recruited to the liver in response to aberrantly expressed endothelial-cell adhesion molecules and chemokines that are normally restricted to the gut (Adams et al., 2006).

There have been reports that certain polymorphisms in the intercellular adhesion molecule-1 (ICAM1) gene are associated with inflammatory bowel disease susceptibility (Braun et al., 2001; Low et al., 2004) and protection against primary sclerosing cholangitis (Yang et al., 2004); however Bowlus et al. (2006) were unable to confirm the latter finding.