Fibronectin in plasma and CSF: evidence for its intrathecal synthesis

A new methodology, using electroimmunodiffusion, has been described for the determination of fibronectin (Fn) in plasma and CSF. Fn was determined in the plasma of 35 normal subjects, and in the plasma and the CSF of 86 patients: 10 controls, 17 definite MS, 15 other inflammatory processes, 11 degenerative diseases, 13 peripheral neuropathies and 20 other neurological diseases. The normal mean was 354 +/- 53 micrograms/ml in plasma, not influenced by sex or age, and in the CSF 2.3 +/- 0.85 micrograms/ml. A significant increase of plasma Fn was observed in each of the patients-group. In the CSF an increase of Fn was observed predominantly in inflammatory processes but not in MS. An intrathecal synthesis of Fn was established in 24/76 patients, most often in inflammatory (9/15) processes but rarely (3/17) in MS. The intrathecal synthesis was suspected from the CSF Fn/CSF Albumin ratio and calculated using a formula derived from the principles previously described for IgG intrathecal synthesis. It represents the principal source of Fn increase in the CSF. In all inflammatory processes (including MS) the eventual influence of corticoids, immunosuppressive or anti-inflammatory drugs has not been established. The significance of the CSF Fn level in MS is discussed with regard to the recent demonstration of its presence within MS lesions and on macrophages in plaques.