RESUMEN
Human plasma contains a number of proteinase inhibitors which together form 10% of the total plasma proteins. Serine proteases are a group of closely related proteolytic enzymes, with serine in their active site. These play a key role in coagulation, fibrinolysin, kinin and complement activation. Serine protease inhibitors or "serpins" are specific inhibitors which control the activities of these enzymes. Among the serine protease inhibitors. Alpha-1 antitrypsin (alpha1 ATD) is found in highest concentration in plasma. It is the major physiologic inhibitor for neutrophil elastase. It has control over the elastase mediated degradation of elastic tissue in the lung. Alpha1ATD deficiency is a common genetic disorder and potentially lethal disease predominantly found in North European population--where the incidence is one in 2500; worldwide figures suggest that one in 6000 people have classic alpha1ATD. In cases of deficiency, antielastase activity is reduced in the lungs which results in increased elastin breakdown and development of emphysema. Cigarette smoking contributes to destructive changes in emphysema by suppressing the proteinase inhibitory activity of human serum and by inducing certain bronchoalveolar changes. Prevalence and severity of asthma increases in persons with abnormal alpha1ATD phenotype.