<unk>  or α1-antitrypsin <unk> , α1AT, A1A, or<unk>  is a protein belonging to the serpin superfamily. It is encoded in humans by the SERPINA1 gene. A protease inhibitor, it is also known as<unk><unk> –proteinase inhibitor (A1PI) or<unk><unk> -antiproteinase (A1AP) because it inhibits various proteases (not just trypsin). In older biomedical literature it was sometimes called serum trypsin inhibitor (STI, dated terminology), because its capability as a trypsin inhibitor was a salient feature of its early study. As a type of enzyme inhibitor, it protects tissues from enzymes of inflammatory cells, especially neutrophil elastase, and has a reference range in blood of 0.9–2.3 g/L (in the US the reference range is expressed as mg/dL or micromoles), but the concentration can rise manyfold upon acute inflammation. When the blood contains inadequate amounts of<unk>  or functionally defective<unk>  (such as in<unk>  deficiency), neutrophil elastase is excessively free to break down elastin, degrading the elasticity of the lungs, which results in respiratory complications, such as chronic obstructive pulmonary disease, in adults. Normally,<unk>  leaves its site of origin, the liver, and joins the systemic circulation; defective<unk>  can fail to do so, building up in the liver, which results in cirrhosis in either adults or children. In addition to binding to neutrophil elastase released by inflammatory cells,<unk>  also binds to elastase localized on the cell surface in which case elastase does not act as an enzyme, but instead acts to signal cells to undergo locomotion. Besides liver cells, A1PI is produced in bone marrow, by lymphocytic and monocytic cells in lymphoid tissue, and by the Paneth cells of the gut. Inactivation of<unk>  by enzymes other than elastase due to inflammation/infection causes the migration of T cells to halt precisely at the site where the pathologic insult exists. This suggests a role for α1PI not only in locomotion of lymphocytes through tissue, but as a consequence of infection, a primary role as a sentinel in immune vigilance.<unk>  is both an endogenous protease inhibitor and an exogenous one used as medication. The pharmaceutical form is purified from human donor blood and is sold under the nonproprietary name<unk><unk> –proteinase inhibitor (human) and under various trade names (including Aralast NP, Glassia, Prolastin, Prolastin-C, and Zemaira). Recombinant versions are also available but are currently used in medical research more than as medication.
Alpha-1 antitrypsin
Haptocorrin
Gamma globulin
Hepcidin
Ovoferrin
Thyroglobulin
Beta defensin
Defensin