Intrathecal synthesis of immunosuppressive acidic protein (IAP) in patients with multiple sclerosis and other inflammatory neurological diseases.

Immunosuppressive acidic protein (IAP), an immunosuppressive substance produced mainly by macrophages, has previously been shown to increase in the serum of patients with inflammatory neurological diseases. In this study we assayed the IAP levels in cerebrospinal fluid (CSF) by a passive hemagglutination-inhibition test. CSF-IAP levels increased significantly in patients with multiple sclerosis (MS) during both the active and inactive stages and in patients with Guillain-Barré syndrome (GBS) or Miller Fisher syndrome (MFS) as compared with those of control patients, but not in patients with amyotrophic lateral sclerosis or spinocerebellar degeneration. During the active stage of MS, increased CSF-IAP levels together with the elevated IAP% (CSF-IAP/total CSF protein) and IAP index [(CSF-IAP/serum IAP)/(CSF albumin/serum albumin)] suggested the intrathecal synthesis of IAP. In contrast, in patients with GBS or MFS, increased CSF-IAP levels without elevation of IAP% could be attributed largely to increased total CSF protein levels. In patients with neuro-Behçet's disease, CSF-IAP levels and IAP% were elevated during the active stage, but remained normal levels during the inactive stage. Assaying CSF-IAP could provide useful information about inflammatory or immunopathological events within the central nervous system.