1. The effects of an aqueous solution of cigarette smoke upon the functional, immunological and electrophoretic assessment of α1-antitrypsin have been studied.
2. The addition of cigarette smoke reduced the inhibitory capacity of the α1-antitrypsin and this was associated with at least a 22% underestimation of the protein concentration by immunological measurement.
3. Furthermore the cigarette-smoke-damaged α1-antitrypsin had an increased electrophoretic mobility in plain agarose compared with the pure protein and was more susceptible to proteolytic damage by elastase.
4. Comparison with results obtained in vivo suggests that oxidative damage to α1-antitrypsin is not the only mechanism involved in the reduction of its inhibitory capacity in secretions, even in non-smokers.