Elevated intrathecal antibodies against the medium neurofilament subunit in multiple sclerosis

Neurofilaments are cytoskeletal proteins localized within axons, which may interact with the immune system during and following tissue destruction in multiple sclerosis (MS). Antibodies against the medium neurofilament subunit synthesized intrathecally may reflect axonal damage in MS patients. Both immunoglobulin G (IgG) and M (IgM) responses against the purified native medium subunit of neurofilaments (NFM) using enzyme-linked immunosorbent assay (ELISA) were determined in paired serum and cerebrospinal fluid samples obtained from 49 MS patients, 16 normal controls (CN), 21 control patients with miscellaneous diseases (CD) and 14 patients with neurodegenerative disorders (CDEG). Intrathecal production of IgM and IgG antibodies to NFM were elevated in MS patients compared with the CN or CD groups (p < 0.04 for IgM, p < 0.01 for IgG). The increase was present in all the MS courses (relapsing-remitting, primary and secondary progressive). Similar local anti-NFM IgG and IgM synthesis occurred in the MS and CDEG groups. MS patients with short and long disease duration did not differ in terms of their anti-NFM IgM and IgG responses. Repeated examinations showed stable intrathecal anti-NFM production. Intrathecal IgG and IgM antibodies against NFM were increased in MS patients and may serve as a potential marker for axonal pathology. The extent of anti-NFM levels did not correspond to any individualized clinical profiles of MS patients.