Nitrocellulose immunofixation following agarose electrophoresis in the study of immunoglobulin G subgroups in unconcentrated cerebrospinal fluid

Higher Levels of IgG3 Antibodies in Serum, But Not in CSF, Distinguish Multiple Sclerosis From Other Neurological Disorders

Increased intrathecal IgG and oligoclonal bands (OCB) are seminal features of multiple sclerosis (MS). Although no such differences in MS blood total IgG antibodies have been reported, serum OCB are a common and persistent finding in MS and have a systemic source. Recent studies showed that IgG3⁺ B cells and higher levels of serum IgG3 are linked to the development of MS. Additionally, intrathecal IgG synthesis in MS is associated with IgG3 heavy chain gene single nucleotide polymorphisms, and there is a strong relationship between susceptibility to MS and an IgG3 restriction fragment length polymorphism. These studies support the role of IgG3 in disease pathogenesis. Using multiple immunoassays, we investigated levels of total IgG, IgG1, and IgG3 in sera and CSF of 102 MS patients (19 paired CSF and sera), 76 patients with other neurological disorders (9 paired CSF and sera), and 13 healthy controls. We show that higher levels of total IgG and IgG3 antibodies were detected in MS serum, but not in CSF, which distinguishes MS from other inflammatory and non-inflammatory neurological disorders, with Receiver Operating Characteristic (ROC) Curves 0.79 for both IgG3 & total IgG. Our data support the notion that IgG3 antibodies may be a potential candidate for MS blood biomarker development.

Cerebrospinal fluid biomarkers in multiple sclerosis

In patients with multiple sclerosis (MS) intensive efforts are directed at identifying biomarkers in bodily fluids related to underlying disease mechanisms, disease activity and progression, and therapeutic response. Besides MR imaging parameters cerebrospinal fluid (CSF) biomarkers provide important and specific information since changes in the CSF composition may reflect disease mechanisms inherent to MS. The different cellular and protein-analytical methods of the CSF and the recommended standard of the diagnostic CSF profile in MS are described. A brief update on possible CSF biomarkers that might reflect key pathological processes of MS such as inflammation, demyelination, neuroaxonal loss, gliosis and regeneration is provided.

Apolipoprotein AI mutation Arg-60 causes autosomal dominant amyloidosis

A mutation in the gene for apolipoprotein AI (apoAI) was identified in an English family with autosomal dominant non-neuropathic systemic amyloidosis. The plasma of all affected individuals contained a variant apoAI with one additional charge, as well as normal apoAI. The propositus was heterozygous; the coding region of his apoAI gene contained both the normal sequence and a single-base substitution changing the codon for residue 60 of the mature protein from CTG (leucine) to CGG (arginine). Allele-specific oligonucleotide hybridization showed that the other affected individuals were also heterozygotes and that there was concordance of the mutant allele with the presence of variant plasma apoAI. Amyloid fibrils isolated from the spleen of the propositus consisted of proteins that ran as a doublet with an apparent mass of approximately 10 kDa in SDS/PAGE and a trace band at 28 kDa. Electrospray mass spectrometry of the purified 10-kDa material revealed components with mass corresponding to the N-terminal 88, 92, 93, and 94 residues of apoAI each with substitution of arginine for leucine. These observations were confirmed by direct protein sequencing and laser desorption time-of-flight mass analysis. No material with the normal apoAI sequence was detected. The trace band at 28 kDa yielded the N-terminal sequence of mature apoAI, indicating that intact or minimally degraded apoAI was also present in the fibril preparation. Discovery of this mutation and the detailed characterization of the apoAI fragments that form the amyloid fibrils open additional avenues for investigation of amyloidogenesis.

Identification of IgG subclasses' oligoclonal bands in multiple sclerosis CSF

IgG subclasses' oligoclonal bands in unconcentrated CSF from MS patients were detected by isoelectric focusing in agarose gel with subsequent immunoblotting using mouse monoclonal antibodies to human IgG subclasses and double-antibody avidin-biotin-alkaline phosphatase system. All MS CSF showed presence of oligoclonal bands specific to the IgG1 subclass; in addition, several of these samples also had oligoclonal bands specific to IgG3, IgG2, or IgG4, in order of decreasing frequency. Since the CSF of a greater number of MS patients showed oligoclonal bands specific to the IgG1 and IgG3 subclasses, the findings are consistent with those reported in patients with chronic viral infections and autoimmune diseases.

IgG1,3 and 4 oligoclonal bands in multiple sclerosis and other neurological diseases

Cerebrospinal fluid (CSF) samples from 10 patients with Multiple Sclerosis (MS) and 7 with other neurological diseases (OND) were studied in order to detect oligoclonal restriction of IgG subclasses 1,3 and 4. Agarose isoelectric focusing (AGA-IEF) followed by Western capillary blotting and immunoperoxidase staining with specific monoclonal antibodies were used. All MS samples showed oligoclonal IgG1 and 6 of them also had IgG3 or IgG4 bands. In the OND group only patients with subacute sclerosing panencephalitis (SSPE) and Guillain-Barré disease (GBD) showed CSF oligoclonal patterns for IgG subclasses. Our results demonstrate that in MS CSF other IgG subclasses beside IgG1 may display an oligoclonal pattern. The finding of more than one subclass in the same band indicates a microheterogeneous composition of these oligoclonal bands.

Rapid blotting of IgG to nitrocellulose with minimal IgM contamination

A rapid method is described for the non-electrophoretic transfer of IgG from 0.5 mm thick agarose gels to nitrocellulose. Since the agarose gels are attached to a solid support, the blot is unidirectional. However, 90% of the IgG is transferred in 10 min with no visible loss of resolution. In this procedure, less than 2% of the IgM antibodies are transferred from the gel to the nitrocellulose membrane. Therefore, this technique can be used in IgG spectrotype analysis or antigen-specific assays without the prior removal of IgM antibodies. Approximately 5-6 h are needed to run the gels, blot, and develop the protein pattern with double-antibody immunoperoxidase staining.

The use of alkaline-phosphatase conjugated second antibody for the enhancement of immunoprecipitation techniques on cellulose acetate membranes

A technique is described using alkaline phosphatase (ALP) conjugated second antibodies on cellulose acetate membrane (CAM) for enhancement of immunoprecipitation techniques. The method is extremely sensitive, detecting as little as 0.1 mg/l of protein and has particular application in the investigation of monoclonal immunoglobulins in human serum or urine and in hybridoma supernatants or ascitic fluids.

A comparison of cellulose acetate immunofixation with polyacrylamide gel electrophoresis for the detection of oligoclonal bands in unconcentrated cerebrospinal fluid

Two methods of electrophoresis for the detection of oligoclonal bands in unconcentrated CSF were compared. A sample of 98 routine CSFs yielded 18 positives by polyacrylamide gel electrophoresis (PAGE) while cellulose acetate electrophoresis with immunofixation (CAIF) gave 13 positives (72% of the PAGE findings). Despite the loss of sensitivity the cellulose acetate electrophoresis was easier to interpret and more suited to a routine hospital laboratory.