Faculty Bibliography

Anti-MAG IgM antibodies were detected by ELISA in a patient with slowly progressive peripheral neuropathy. Serum IgM content was normal, and no M-protein was detected by serum protein electrophoresis, immunoelectrophoresis, or immunostaining. By immunoblot analysis, the anti-MAG antibodies were IgMk; they reacted with human and bovine MAG but not with mouse MAG. The data suggest that there was an anti-MAG IgM M-protein in concentration too low to be detected by conventional techniques. Tests for anti-MAG antibodies should be done in patients with slowly progressive neuropathy of unknown etiology, even in the absence of detectable serum M-protein.

In some patients with plasma cell dyscrasia and neuropathy, there are IgM M proteins that react with the myelin-associated glycoprotein (MAG). We used an enzyme-linked immunosorbent assay (ELISA) system to detect anti-MAG IgM antibodies. Reactivity with human MAG by ELISA correlated with demonstration of anti-MAG IgM antibodies by the "immunoblot" technique. Human MAG was more effective than bovine MAG as antigen, and there was no significant reactivity with mouse MAG. The ELISA system is a simple and convenient method for detecting anti-MAG IgM antibodies.

Immunoglobulins were conjugated to peroxidase by the biotin-avidin method and used in ELISA systems for measuring myelin basic protein (MBP) and anti-MBP antibodies. To measure concentration of MBP, microplate wells were coated with affinity purified rabbit anti-MBP antibodies and incubated with varying concentrations of MBP. Bound antigen was measured by incubating with biotinylated anti-MBP antibodies and avidin-peroxidase. As little as 0.2 ng/ml of MBP could be measured by this assay. To measure anti-MBP antibodies, microplate wells were coated with human MBP and incubated with varying concentrations of affinity purified rabbit anti-human MBP antibodies. Binding was measured by incubating with either peroxidase-conjugated anti-rabbit antibodies or biotinylated anti-rabbit antibodies and avidin peroxidase. The two methods were equally sensitive. The avidin-biotin method for enzyme conjugation promises to be a useful and versatile tool for ELISA systems.