Studies into the occurrence of soluble antigen-antibody complexes in disease. VIII. Fractionation of rheumatoid samples containing immune complex-like material.

Fractionation studies were performed of an immune complex-like material measured in rheumatoid synovial fluid using a biological assay based on histamine release from guinea pig lung. This material was eluted from Sepharose 6B in the excluded fraction, from DEAE cellulose predominantly in the third buffer, and from polyacrylamide electrophoresis in a cathodal position. Heterogeneity of the complexes was evident on iso-electric focussing, with one peak of activity at a pH of 4.2--5.6 and the other at pH 6.8--8.6. Purification of the material was limited by a loss of activity which occurred on using three fractionation procedure in sequence. This instability was avoided in the case of Sepharose 6B by adding 0.1% bovine or rabbit albumin to the elution buffer.