Rapid recruitment of inflammatory monocytes is independent of neutrophil migration.
Early neutrophil entry into an inflammatory site is thought to mediate a chemokine switch, inducing subsequent monocyte recruitment through the regulation of monocyte chemoattractant protein-1 (MCP-1) release. As the murine monocyte is poorly characterized and difficult to identify, there has been little examination of either its early recruitment in inflammatory models or of the factors that influence its early migration. The phenotyping of rapidly recruited inflammatory leukocytes with 7/4 and Gr-1 monoclonal antibodies (mAbs) identifies 2 distinct populations, which we characterize as murine monocytes and neutrophils. Monocytes migrate in the first 2 hours of inflammation making use of alpha4beta1 but not of Mac-1 or lymphocyte function-associated antigen-1 (LFA-1) integrins. Early migration is dependent on MCP-1, but neither MCP-1 release nor monocyte recruitment is affected by the reduced neutrophil migration seen in LFA-1-/- mice. Endogenous peritoneal macrophages and mesothelial cells lining the peritoneum contain MCP-1, which is released following thioglycollate stimulation. The murine monocyte therefore responds rapidly to chemokines produced in situ by tissue cells at the site of inflammation with no requirement for prior influx of neutrophils.
Henderson
Robert B
RB
Leukocyte Adhesion Laboratory, Cancer Research United Kingdom London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3PX, UK.
Hobbs
Josie A R
JA
Mathies
Meg
M
Hogg
Nancy
N
D000818:Animals; D002450:Cell Communication; D018932:Chemokine CCL2 / Q000032:analysis / Q000096:biosynthesis; D002634:Chemotaxis, Leukocyte; D007249:Inflammation / Q000276:immunology / Q000473:pathology; D039441:Integrin alpha4 / Q000502:physiology; D016169:Lymphocyte Function-Associated Antigen-1 / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009000:Monocytes / Q000166:cytology*; D020556:Neutrophil Infiltration; D010538:Peritonitis / Q000276:immunology / Q000473:pathology
D018932:Chemokine CCL2; D016169:Lymphocyte Function-Associated Antigen-1; D039441:Integrin alpha4