Fig 5.

2D sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the circulating immune complexes (CIC) purified from systemic lupus erythematosus (SLE) patients. The first dimension isoelectric focusing (IEF) was carried out using immobilized pH gradient (IPG) immobiline strip pH 3–10 linear gradient. The second-dimension run was performed on 4–12% gradient SDS-PAGE gel. The spots for both heavy and light chains of human globulins are marked. Both the γ chain and µ chain, in addition to ι and κ light chains, were identified by comparison of gel images with National Biological Research Foundation (NBRF) 2D database. The identity of these spots was also confirmed using Western blot analysis and MASS analysis. 2D SDS-PAGE profile of heavy chains in one patient (a) demonstrated the presence of both IgG and IgM containing CIC, while in the other patient CIC were composed mainly of IgM isotype (b). The patient with CIC composed of both immunoglobulin isotype also demonstrated a broader light chain profile in comparison to CIC composed of only IgM isotype.