Expression and secretion of type beta transforming growth factor by activated human macrophages.

TLDR

Monocytic cells such as U937 lymphoma cells constitutively express TGF‑beta mRNA, whereas other growth factor genes like the B chain of platelet‑derived growth factor require activation. Activation of monocytes/macrophages with concanavalin A or lipopolysaccharide induces TGF‑beta secretion, whereas unactivated cells secrete little TGF‑beta despite comparable mRNA, and both cell types release an acid‑labile binding protein that can inhibit TGF‑beta action.

Abstract

Alveolar macrophages activated with concanavalin A and peripheral blood monocytes activated with lipopolysaccharide secrete type beta transforming growth factor (TGF-beta). There is minimal TGF-beta secretion in unactivated monocytes, even though TGF-beta mRNA is expressed in these cells at a level similar to that in activated, lipopolysaccharide-treated cultures. U937 lymphoma cells, which have monocytic characteristics, also express mRNA for TGF-beta. Freshly isolated monocytes, both control and lipopolysaccharide-treated, secrete an acid-labile binding protein that inhibits TGF-beta action. We conclude the following: (i) that expression of TGF-beta mRNA is unrelated to monocyte activation, (ii) that secretion of TGF-beta is induced by monocyte activation, and (iii) that cosecretion of TGF-beta and its monocyte/macrophage-derived binding protein may modulate growth factor action. In contrast, monocytic expression of other growth factor genes, such as the B chain of platelet-derived growth factor, is not constitutive and requires activation.