Sandwich electroimmunofixation (SEIF) for the assessment of isoenzyme specificities of immunoglobulins isolated from enzyme-immunoglobulin complexes.

Sandwich electroimmunofixation (SEIF) was used to determine immunologic specificity for isoenzymes of immunoglobulins isolated from enzyme-immunoglobulin complexes. After electrophoretic separation of isoenzymes, isoenzyme-specific human immunoglobulins obtained from complexes and antihuman immunoglobulin antibodies were applied to the supporting medium and allowed to react. Complexes of isoenzyme-immunoglobulins-anti-immunoglobulin antibodies formed immunoprecipitates and were fixed in the supporting medium. After washout of the unreacted enzymes and proteins with buffer, the immunoprecipitates were stained. A comparison with control enzymograms allowed for a determination as to whether the immunoglobulins reacted with specific isoenzymes. When an immunologic reaction with more than 2 isoenzymes occurred, the specificity was quantitated by densitometry. SEIF, used to examine immunoglobulins isolated from aspartate aminotransferase-, lactate dehydrogenase-, alkaline phosphatase- and amylase-immunoglobulin complexes, was found to be a rapid and reliable technique. This approach showed that immunoglobulins differ in their specificities for various isoenzymes.