Conventional isoelectric focusing does not dissociate immune complexes.

Contrary to some reports, isoelectric focusing (IEF) is unable to dissociate immune complexes (IC) into their constituent components. Six model IC systems prepared at various antigen/antibody ratios were readily dissociated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), but not by conventional IEF, independently of several modifications of the running conditions. IC preformed in situ in the IEF gel were not disrupted by subsequent electrophoresis. Moreover, formation of IC was demonstrable in IEF, when applying antigen and antibody preparations in the manner used for counterimmune electrophoresis. Nevertheless, IEF may be of value in the analysis of IC provided the complexes are of small enough size to enter the gel.