Quantification of human immunoglobulins by semiautomatic polyethylene glycol precipitation radioimmunoassays. Estimation of circulating immune complexes and immunoglobulin synthesized in vitro.

Simple, reliable semiautomatic radioimmunoassays have been developed for the measurement of human immunoglobulins (IgG, IgA, IgM, IgK and Ig lambda). The assays are based on the separation of free from antibody-bound radiolabelled fragments of immunoglobulin by precipitation with 13% polyethylene glycol. The precipitate is harvested and washed on glass fibre filters by means of a commercial cell harvester. Radiolabelled lambda chain from Bence Jones urine was used for lambda chain assay and Fab' gamma from pooled IgG for the kappa assay. Labelled Fab or Fc fragments of IgG, IgA and IgM were used for the class specific assays. Selected commercial antisera were used throughout. The sensitivity limits of the assays performed according to the standard procedure were about 20 ng Ig per ml. The assays have been used for the quantification of circulating immune complexes and both cellular and secreted immunoglobulin produced in cell cultures. The results demonstrate the importance of the simultaneous quantification by L chain and H chain specific assays.