Intradermal injection of monocyte chemoattractant protein-1 induces emigration and differentiation of blood monocytes in rat skin.
BACKGROUND
Monocyte chemoattractant protein-1 (MCP-1) is a potent chemoattractant for blood monocytes in vitro. Recent studies in MCP-1-transgenic mice revealed that the local production of MCP-1 caused monocyte infiltration. However, the kinetics of monocyte infiltration after the production of MCP-1 or the amount of MCP-1 necessary for monocyte recruitment are not known.


METHODS
We purified recombinant rat MCP-1 expressed in COS-7 cells, and injected it into rat skin. The infiltrating cells were examined by immunohistochemistry and ultrastructural peroxidase cytochemistry.


RESULTS
Rat recombinant MCP-1 had a molecular mass of approximately 30 kD and exhibited the peak monocyte chemotactic activity at 10(-9) M. One microgram of MCP-1 caused intra- and extravascular accumulation of mononuclear cells 3 h after injection. The cells were ED1+, indicating they were blood monocytes. The infiltration of mononuclear cells peaked at 12-24 h, and most of them were TRPM-3+ and ED3+, characteristic to exudate macrophages. None of the cells expressed ED2 or Ki-M2R antigens, markers for resident macrophages, until 3 days after injection. There was no uptake of [3H]thymidine by the infiltrating cells. Ultrastructural peroxidase cytochemistry confirmed that the infiltrating cells were monocytes and exudate macrophages. The number of OX8+ lymphocytes also peaked at 12 h, consisting of approximately 9% of the total infiltrating cells.


CONCLUSIONS
These results indicate that MCP-1 attracts blood monocytes as early as 3 h and the infiltrating monocytes differentiate into exudate macrophages in loco. However, this effect was transient and the infiltration of monocytes did not result in tissue damage.
Yamashiro
S
S
Second Department of Pathology, Kumamoto University School of Medicine, Japan.
Takeya
M
M
Kuratsu
J
J
Ushio
Y
Y
Takahashi
K
K
Yoshimura
T
T
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001808:Blood Vessels / Q000276:immunology; D019556:COS Cells; D002452:Cell Count; D002454:Cell Differentiation; D002465:Cell Movement; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D002634:Chemotaxis, Leukocyte; D007150:Immunohistochemistry; D007962:Leukocytes / Q000166:cytology / Q000276:immunology; D008214:Lymphocytes / Q000166:cytology / Q000276:immunology; D008264:Macrophages / Q000276:immunology / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D009000:Monocytes / Q000166:cytology / Q000276:immunology* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D012867:Skin / Q000276:immunology / Q000473:pathology / Q000648:ultrastructure; D013047:Specific Pathogen-Free Organisms
D000911:Antibodies, Monoclonal; D018932:Chemokine CCL2; D011994:Recombinant Proteins