| Abstract: | A solid-phase radioimmunoassay (RIA) for IgM anti-HBc is described. The assay (anti-m? RIA) is based on the adsorption of IgM to a tube coated with sheep antibody to the human IgM m?-chain. The adsorbed immunoglobulin is assayed for anti-HBc activity. Positive reactions in the test are shown to be due to IgM antibody, and a confirmation blocking test is described. Reactivity of test sera can be quantitated by comparison with standard sera containing known levels of IgM anti-HBc. Sera assayed for IgM anti-HBc by both the anti-m? RIA and a method employing serum fractionation and competitive RIA gave similar results. Rheumatoid factor (RF) alone did not react in the anti-m? RIA, but reactivity could be generated in the presence of RF and preformed aggregates of IgG anti-HBc. |
