Studies on circulating soluble immune complexes of the liver disease. 1. Inhibition assay of polyclonal rheumatoid factor binding to IgG-sepharose.

Polyclonal rheumatoid factor (pRF) was isolated from sera seropositive for RF and it was radioiodinated with lactoperoxidase method. Using the 125I-pRF and IgG-p-azobenzamidoethyl Sepharose 6B, a competitive inhibition radioassay for detecting immune complexes is described. The assay can be performed in 90 min utilizing 10 microliter of serum with good reproducibility and endogenous RF in test serum did not interfere the reaction. The test can detect complexes nearly to 8s and as low as 0.1 microgram/ml of aggregated human IgG. Decomplementation by heating test sera is unnecessary. The assay was performed at 4 degrees C but less inhibition activity was obtained when it was carried out at 24 degrees C.