Immune response in progressive multifocal leukoencephalopathy: An overview

Progressive multifocal leukoencephalopathy (PML) is a disease usually ocurr ing in immunosuppressed patients. By far the most common underlying immunos uppressive illness is the acquired immune deficiency snydrome, accounting f or about 85% of PML cases currently seen in clinical practice. PML may occu r in patients with deficits in the humoral and/or cellular immune response such as lymphoproliferative diseases, myeloproliferative diseases, carcinom atous diseases and acquired immunodeficiency due to autoimmune diseases and immunosuppressive therapy. The humoral immune response in PML is indicativ e of a persistent, reactivated infection with a prominent immunoglobulin (I gG) G synthesis to virus protein 1 (VPI). An I-M synthesis in serum is rare ly found. In about 76% of PML cases, an intrathecal humoral immune response to recombinant VP1 can be found as compared to only 3.2% in healthy contro ls. The detection of intrathecally synthesized IgG antibodies to VP1 can be used as an additional diagnostic test for the diagnosis of PML. The magnit ude of the intrathecal Immoral immune response appears to rise over time an d may be associated with a decrease of viral load in cerebrospinal fluid (C SF) and possibly the central nervous system (CNS). Compared to healthy cont rols, proliferation of peripheral blood mononuclear cells (PBMC) is reduced in PML patients. Immunological studies suggest a general impairment of the Th1-type T-helper cell function of cell-mediated immunity Furthermore, the appearance of JCV-specific cytotoxic T-lymphocytes appears to be associate d with a favorable clinical outcome.