Expression of the α1-proteinase inhibitor (α1PI) gene was studied in human mononuclear cells. Using RNA blot and dot hybridization, α1PI mRNA was detected in human peripheral blood monocytes, bronchoalveolar and breast milk macrophages, but not in B or T lymphocytes. Using incorporation of a radiolabeled amino acid precursor, synthesis and secretion of α1PI were demonstrated in human monocytes and macrophages, but not in lymphocytes. In addition, α1PI was secreted in functionally active form as shown by complexing with serine proteases. Biosynthesis of α1PI by mononuclear phagocytes was greatest during the first 24 hr in culture and progressively decreased over the next 10 days. The reduction in α1PI biosynthesis in vitro involved a mechanism acting at the pretranslational level as α1PI mRNA content also progressively declined over 10 days in culture. The ease of sampling human monocytes and macrophages now permits examination of the biochemical defect in homozygous PiZ and PiS α1PI deficiencies and study of the functional significance of locally produced α1PI in normal tissues and sites of injury or inflammation.

Original languageEnglish
Pages (from-to)795-799
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number3
StatePublished - 1985


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