We have studied expression of α1-protease inhibitor (α1-PI) by human mononuclear cells. α1-PI was detected on 50% of freshly isolated peripheral mononuclear cells. Unless a proliferative stimulus was provided, α1-PI subsequently disappeared from the cell surfaces. Plant mitogens, periodate, neuraminidase-galactose oxidase, or allogeneic cells all were effective stimuli of α1-PI expression. Concanavalin A stimulated de novo synthesis of α1-PI in cell cultures containing both lymphocytes and mononuclear phagocytes, and α1-PI simultaneously appeared on surfaces of activated lymphocytes. Inhibition of protein synthesis by cycloheximide or monocyte depletion abolished de novo α1-PI synthesis, but only monocyte depletion inhibited α1-PI expression. Lymphocytes, but not monocytes, displayed saturable binding of radioiodinated α1-PI. The data are consistent with the interpretation that human mononuclear phagocytes synthesize and secrete α1-PI. When protein synthesis is inhibited, mitogenic stimuli may provoke release of previously synthesized α1-PI from mononuclear phagocytes. Secreted α1-PI then may bind to specific lymphocyte cell surface receptors. This pattern of α1-PI synthesis, secretion, binding, and expression on lymphoid cell surfaces appears to be a common characteristic of many immunologic reactions in vitro.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of Immunology|
|State||Published - Jan 1 1982|
ASJC Scopus subject areas
- Immunology and Allergy