A sensitive assay to evaluate antistreptococcal antibodies using an in vitro-produced monoclonal human rheumatoid factor.

A human monoclonal rheumatoid factor (RF) produced in vitro by an Epstein-Barr virus (EBV) immortalized cell line is used in an assay to detect and quantitate antibodies directed against streptococcal antigens in human sera. The assay, based on the binding of the rheumatoid factor to IgG-immune complexes, applies this monoclonal antibody in its iodinated form. The assay can easily quantitate IgG-antistreptococcal antibodies and enables the quantitation of these specific antibodies in sera that contain even very low titers.