Isoelectric focusing--a new approach to the study of immune complexes.

Isoelectric focusing was used to examine antigen-antibody complexes. BSA : anti-BSA complexes were dissociated and antigen was separated from antibody based upon differences in pI value by isoelectric focusing (pH gradient 3--10). The recovered proteins were homogeneous as determined by immunodiffusion and polyacrylamide gel electrophoresis analyses. The technique was capable of resolving 6.4 microgram of BSA : anti-BSA complexes. More than 90% of the complexes applied to isoelectric focusing gels were dissociated and entered the gels. It was further demonstrated, by the use of complexes containing enzymes (acid phosphatase or alkaline phosphatase), that the dissociated enzymes retained their native pI as well as enzymatic activities. The isoelectric focusing technique, therefore, represents a new and effective approach to the dissociation of antigen-antibody complexes.