Letter: Multiple sclerosis with hypocomplementaemia

Terminal component of complement C9 in CSF and plasma of patients with MS and aseptic meningitis

A sensitive sandwich ELISA was applied to the measurement of the terminal component of complement C9 in CSF and plasma from 40 tension headache patients (reference group), 33 affected by clinically definite MS and 10 by aseptic meningitis. The levels of C9 in plasma were increased in aseptic meningitis. The determinations of CSF/plasma C9 ratio and C9 index, equal to (CSF C9/plasma C9): (CSF albumin/plasma albumin), thus accounting for changes of plasma C9 levels as well as damaged blood brain barrier, documented the existence of local consumption of C9 in aseptic meningitis. In contrast, only borderline alterations were evident in MS. The results indicate that local consumption of total C9 in CSF is an additional variable reflecting an acute inflammation within the CNS, but not demonstrable in MS, a chronic inflammatory CNS disorder.

Intrathecal complement activation in neurological diseases evaluated by analysis of the terminal complement complex

The terminal complement complex (TCC) was determined in plasma and cerebrospinal fluid (CSF) from 208 neurological patients. Elevated CSF TCC levels were observed in higher frequencies in patients with infectious diseases (80%), radiculoneuritis (62%), multiple sclerosis (30%), and miscellaneous autoimmune diseases (27%) than in patients with miscellaneous non-inflammatory diseases (2-13%). The plasma level of TCC was significantly increased only in the infectious group. No positive correlation was observed between the plasma and the CSF TCC concentration in the whole patient population nor in subgroups divided according to blood-brain barrier function. Furthermore, the CSF TCC concentration did not correlate with the serum/CSF albumin ratio or with CSF total protein concentration when this was below 1.0 g/l. It is concluded that an elevated TCC concentration in CSF reflects intrathecal complement activation and that quantification of TCC in CSF may be a valuable supplement in the examination of neurological diseases.

Isolation of membrane attack complex of complement from myelin membranes treated with serum complement

The interaction between complement and myelin membranes and its possible role in myelin damage and in the disposal of damaged myelin in vivo is of interest because activation of complement generates both opsonin(s) and membrane attack complex of complement. In our studies on the role of complement in demyelination, we have shown that isolated myelin activates serum complement in the absence of myelin-specific antibody and that membrane attack complex of complement is the required factor in antibody-mediated demyelination of mouse cerebellar explant cultures. In the present study, we examined whether activation of serum complement by myelin is associated with the formation of membrane attack complex of complement in myelin membranes. Extracts of myelin-associated proteins following incubation of myelin with fresh serum were studied by ultracentrifugation on a sucrose density gradient for detection of C5b-9 neoantigen. The subunit structure of C5b-9 was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, electroblotting, and immunostaining. Results indicate that the macromolecular complex consisting of late-acting complement components, C5-C9, was assembled in the target myelin membranes.

C3 polymorphism and circulating immune complexes in patients with multiple sclerosis

The phenotypes of the complement factor C3 have been evaluated in 60 patients with multiple sclerosis (M.S.), and the results correlated to the occurrence of circulating immune complexes (CIC). A significantly increased frequency of the C3F-gene was found among the patients, and closely associated with the occurrence of CIC. A relative risk incidence of 4.1 was found for C3F-positive individuals among M.S. patients with detectable CIC. Low C3 levels in serum were found in 30% of the patients, almost all belonged to the group without CIC and showed a C3-type distribution similar to normal controls. A different immunological reaction pattern (type II reaction) in these patients seems possible, and a genetically determined immunological abnormality predisposing to M.S. is therefore suggested.

Hypocomplementaemic and normocomplementaemic multiple sclerosis. Genetic determinism and association with specific HLA determinants (B18 and B7)

Seventy-five patients with multiple sclerosis (MS) were treated for complement components C3, after factor B, C4, and tested for HLA-A and B-determinants. Levels of IgG, IgA, IgD, IgE and titres of measles antibodies were also determined. Correlations between these immunological values and HLA determinants could be obtained in siblings, parents and/or children of the patients in 13 families. B18 frequency is strongly associated with the hypocomplementaemic group (x2 = 8.9). An association of B18 with the population of cases with low B levels is also found (x2 = 8.02). Familial data showed that low C3 and/or low B levels are associated with the HLA haplotyes, especially with those containing B18. A "complement abnormality susceptibility gene", linked to the HLA genes, is postulated. Infections are significantly more frequent in families of hypocomplementaemic MS, the existence of a genetic immunodeficiency affecting the synthesis of the complement components, linked to the HLA determinants. In 1 case studied in this article, a heterozygous C2 deficiency linked to HLA-A10, B18 was found and might confirm this hypothesis.

Host resistance to lipopolysaccharides in the pathogenesis of multiple sclerosis and membranoproliferative glomerulonephritis

Host resistance against bacterial lipopolysaccharides (L.P.S.) and especially against its toxic part lipid A has earlier been demonstrated in biological assays. In this paper an aryl-esterase is shown to be associated with alfa-1-lipoprotein (ArE) and is probably responsible for the detoxification of L.P.S. in man. Furthermore C3 is shown to be activitated by L.P.S. From these facts it is suggested that ArE performs the initial degradation of L.P.S. followed by complement activation and trapping of the L.P.S.--complement complex in the reticuloendothelial system. It is postulated that a deficient host response against L.P.S. can be the triggering mechanism in multiple sclerosis due to the lack of ArE in myelin, and that an infectious-agent/L.P.S. syndrome can activate latent infections in connection with a severe hyperreactivity to L.P.S. Preliminary investigations in patients with membranoproliferative glomerulonephritis have shown low levels of ArE in serum. This change, together with the low C3 values in these patients, may result in deficient L.P.S. detoxification and it is suggested that L.P.S. are at least partly responsible for the production of C3 nephritic factor.