1. Two-dimensional immunoelectrophoresis and conventional sodium dodecyl sulphate-polyacryl-amide gel electrophoresis was performed on various mixtures of purified α1-antitrypsin (α1AT) and leucocyte elastase (LE).

2. The results confirm that α1AT inhibits LE by the formation of enzyme-inhibitor complexes demonstrable by both techniques.

3. The complexes break down with time and are not affected by pH in the presence of excess α1AT. However, the breakdown is more rapid in the presence of excess enzyme only at pH values where LE remains active. The resultant products of the complex breakdown include inactivated LE and α1AT that has undergone limited proteolysis.

4. It is concluded that the presence or absence of α1AT-enzyme complexes as demonstrated by two-dimensional immunoelectrophoresis must be interpreted with caution when studying α1AT function in lung secretions. The absence of such complexes does not mean that previous interaction with enzyme has not occurred, thereby accounting for a reduction in α1AT inhibitory capacity.

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