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Mucosal IL‐8 and TGF‐β recruit blood monocytes: evidence for cross‐talk between the lamina propria stroma and myeloid cells
Author(s) -
Smythies Lesley E.,
Maheshwari Akhil,
Clements Ronald,
Eckhoff Devin,
Novak Lea,
Vu Huong L.,
MostellerBarnum L. Meg,
Sellers Marty,
Smith Phillip D.
Publication year - 2006
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1189/jlb.1005566
Subject(s) - biology , lamina propria , immunology , myeloid cells , stroma , myeloid , transforming growth factor , microbiology and biotechnology , pathology , epithelium , immunohistochemistry , genetics , medicine
The lamina propria of the gastrointestinal mucosa contains the largest population of mononuclear phagocytes in the body, yet little is known about the cellular mechanisms that regulate mononuclear cell recruitment to noninflamed and inflamed intestinal mucosa. Here, we show that intestinal macrophages do not proliferate. We also show that a substantial proportion of intestinal macrophages express chemokine receptors for interleukin (IL)‐8 and transforming growth factor‐β (TGF‐β), and a smaller proportion expresses receptors for N ‐formylmethionyl‐leucyl‐phenylalanine and C5a, but, surprisingly, they do not migrate to the corresponding ligands. In contrast, autologous blood monocytes, which express the same receptors, do migrate to the ligands. Blood monocytes also migrate to conditioned medium (CM) derived from lamina propria extracellular matrix, which we show contains IL‐8 and TGF‐β that are produced by epithelial cells and lamina propria mast cells. This migration is specific to IL‐8 and TGF‐β, as preincubation of the stroma‐CM with antibodies to IL‐8 and TGF‐β significantly blocked monocyte chemotaxis to the stromal products. Together, these findings indicate that blood monocytes are the exclusive source of macrophages in the intestinal mucosa and underscore the central role of newly recruited blood monocytes in maintaining the macrophage population in noninflamed mucosa and in serving as the exclusive source of macrophages in inflamed mucosa.