Previous studies have shown that assessment of immunoglobulin subclasses in plasma cells by immunohistochemistry (IHC) may be useful in the histopathologic evaluation of autoimmune liver diseases.
However, further studies are necessary in order to validate the diagnostic utility of IgM and IgG immunohistochemistry in this specific scenario.
A research team from United States evaluated the predominant plasma cell immunoglobulin subclass present in liver biopsies of patients with well-established autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), or primary sclerosing cholangitis (PSC) and assessed the diagnostic utility of IgM and IgG IHC in this setting. Their study will be published on January 28, 2010 in the World Journal of Gastroenterology
Their research demonstrated that while the plasma cell-rich infiltrates seen in several forms of liver disease predominantly express IgG, PBC seems to be an exception, as most plasma cells in these patients express IgM. Their data indicated that a predominantly IgM+ plasma cell infiltrate, although not pathognomonic, should strongly support the diagnosis of PBC. The IgM/IgG ratio is particularly helpful distinguishing PBC from AIH.