Abstract
A previous report that C3 activation products are demonstrable in the plasma of subjects with rheumatoid arthritis was reinvestigated using 2-dimensional immunoelectrophoresis. Initially it seemed that results were in agreement, but the occurrence of similar patterns in normal sera and poor reproducibility of results suggested the findings were artefacts. When calcium and magnesium ions were removed with EDTA, C3 activation products were no longer demonstrable in plasma from normal subjects or from patients with rheumatoid arthritis. The results obtained without EDTA in the buffer showed a greater degree of complement activation in patients with rheumatoid arthritis, suggesting that in this condition the serum may have a greater potential ability to bring about complement activation.