QUANTITATION OF CIRCULATING IMMUNE-COMPLEXES IN SERUM BY RAJI CELLS USING AN ENZYME-LINKED IMMUNOSORBENT-ASSAY

Abstract

An enzyme-linked immunosorbent assay (ELISA) for the quantitation of immune complexes in sera was developed, using Raji [human lymphoblastoid] cells. In this assay, the Raji cell-adherent complexes are detected by an alkaline phosphatase-conjugated rabbit anti-human Ig[immunoglobulin]G and the results are obtained by spectrophotometric measurements of the concentration of yellow color produced after the enzyme''s substrate, p-nitrophenylphosphate, is added. This assay is as sensitive and reproducible as the Raji cell radioimmune assay using 125I; it can detect as little as 16 .mu.g of immune complex equivalent to heat-aggregated IgG/ml in serum samples. This method is inexpensive, convenient and avoids the biohazards of using an isotope.