Immune complexes in Hodgkin's disease: isolation, immunochemical and physico-chemical analysis.

Immune complexes (IC) present in sera from patients with Hodgkin's disease (HD) were isolated using three different affinity columns: C1q-degalan, anti-C1q sepharose and conglutinin (K)-degalan. The isolated IC were analysed by immunoprecipitation, SDS-PAGE and sucrose density gradients and compared with IC similarly isolated from patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and in vitro prepared BSA-anti-BSA complexes. Isolated material from each disease, and BSA-anti-BSA complexes contained proteins compatible with true immune complexes--IgM, IgG, C1q and C3 breakdown components. Albumin, fibronectin and CRP, whose affinity for IgM, C1q and C3 are known, were co-isolated along with IC material. The size of isolated IC in HD ranged from 8-40S on sucrose density gradients. Despite the operational difference in detecting and isolating HD complexes via the C1q ligand (C1q-degalan or anti-C1q column) and C3bi (K-degalan), material purified by both methods showed remarkable similarity on SDS-PAGE and immunoprecipitation analysis. Although IC isolated from different diseases showed disparate banding patterns on SDS-PAGE this was attributed to a variation in the relative concentrations of constituent proteins--IgM, IgG and C3 breakdown products. IgM, IgG and C3 bind loosely, and non-specifically, to macromolecular aggregates formed around immune complexes. Using the anti-C1q column, most of this material could be eluted using 0.02M EDTA. Least protein, yet the most specific for antigen and antibody was eluted at pH 3.0.

Anti-C1q column: ligand specific purification of immune complexes from human serum or plasma. Analysis of the interaction between C1q and immune complexes.

An efficient and reproducible procedure has been developed for the specific isolation of immune complexes. PEG precipitation of EDTA serum or plasma was an essential preliminary step to separate complex-bound from free C1q. PEG had no discernible effect on the molecular weight size of the extracted complexes. Redissolved complexes were incubated with a Sepharose-4B column coated with anti-human C1q antibodies and following removal of unbound material the bound complexes were sequentially eluted with 0.02 M EDTA, 0.5 M NaCl and 1 M propionic acid. Characteristics of the affinity column were established by the purification of 125I-labelled BSA-anti-BSA complexes and heat-aggregated IgG (HAGG) incubated in normal human serum (NHS). EDTA and NaCl eluted complexes were of similar molecular size and contained antigen, specific antibody, as well as human IgM, IgG, albumin, C3, C3c, C3d and C1q. Acid eluted complexes contained the highest yield of specific antigen and antibody and comprised in addition human C1q and C3d. Activation of complement components after C1q made the bond between C1q and immune complexes resistant to 0.5 M NaCl and interfered with the binding between solid phase anti-C1q and complex bound C1q. Using BSA-anti-BSA complexes and HAGG activated in NHS it was apparent that only a minority of the complexed material was isolated via the C1q ligand and this probably applies to the C1q binding assay. Most complexed material could be isolated using an anti-C3 affinity column.

Application of 125I-labelled second antibody to the solid-phase immunoassay of norethisterone in plasma.

The concept of employing 125I-labelled second antibodies for making quantitative measurements of small molecules in biological fluids was evaluated. In a model system 125I-labelled second antibodies were used to monitor the binding of purified norethisterone antibodies to albumin-norethisterone complexes immobilised upon plastic tube surfaces. Conditions were established to provide an assay response similar to other immunoassays for norethisterone using the same primary antiserum. The specificity and accuracy of the assay were comparable to the conventional solid and liquid-phase assays, but precision tended to be less at low levels of norethisterone (less than 200 pg/tube). A reduction in assay variance may be achieved through more efficient tube-washing procedures.