Why do cryoglobulins form with HCV and not HBV?
HBV is a hepatotropic virus, meaning it selectively and primarily enters hepatic tissue, possibly infects kidney tissue, but does not invade immunocompetent cells. HCV is not only hepatotropic but also lymphotropic, having an affinity to bind to select receptors on B cells and even enter the cell itself. The viral capsid antigens appear to be able to target B-cell receptors that are responsible for cell proliferation, and disrupt the normal cell cycle. Infected B cells in HCV become clonal and produce the IgMk antibody that has anti-idiotypic capacity. HBV and no other form of viral hepatitis has this propensity to bind to and stimulate B cells, which is why cryoglobulins are common in 50% of HCV patients and extremely rare in HBV.
Over time, patients with HCV who have cryoglobulinemia are at higher risk for the development of B-cell lymphoma. The finding of type II cryoglobulinemia in HCV should be regarded as a premalignant disease. Approximately 6% will develop lymphoma.
