Production of IL-8 and monocyte chemotactic peptide-1 by peripheral blood monocytes. Disparate responses to phytohemagglutinin and lipopolysaccharide.
The temporal recruitment of leukocytes to a site of inflammation is dependent on a complex interplay of a number of soluble mediators. Recently, two families of chemotactic cytokines have been discovered. The -C-X-C-family, which includes IL-8, appears to recruit neutrophils and lymphocytes. In contrast, the -C-C-family, which includes monocyte chemotactic peptide-1 (MCP-1), appears to recruit predominantly monocytes. Monocytes, after their arrival at a site of inflammation, could further amplify the immune response by secreting IL-8 and MCP-1. We sought to define conditions under which human peripheral blood monocytes produce IL-8 and MCP-1. Using serum-free media, we found that PHA-stimulated monocytes expressed MCP-1 and IL-8 protein and mRNA in a dose-dependent manner. However, the onset of mRNA expression for MCP-1 occurred at least 3 h later than did the onset of IL-8 mRNA expression. IL-8 and MCP-1 gene expression by monocytes appeared to require de novo protein synthesis, in that cycloheximide blocked the expression of mRNA for both IL-8 and MCP-1 in PHA-stimulated cells. However, treatment of monocytes with cycloheximide resulted in the superinduction of IL-8 compared with control monocytes. Monocytes costimulated with PHA and LPS demonstrated enhanced amounts of IL-8 mRNA and protein, but sharply decreased amounts of MCP-1 mRNA and protein. The addition of serum to culture media increased both the constitutive and PHA-induced production of monocyte-derived MCP-1 and IL-8, but had no effect on the inhibition of PHA-stimulated MCP-1 production by LPS. These findings suggest that distinct pathways of activation exist for the production of monocyte-derived IL-8 and MCP-1. The differential expression of these different but related polypeptides may offer a means of control of the type of immune cells that are recruited to a site of inflammation.
Liebler
J M
JM
Department of Medicine, Oregon Health Sciences University, Portland 97201-3098.
Kunkel
S L
SL
Burdick
M D
MD
Standiford
T J
TJ
Rolfe
M W
MW
Strieter
R M
RM
D001483:Base Sequence; D018932:Chemokine CCL2; D002630:Chemotactic Factors / Q000096:biosynthesis*; D006801:Humans; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology; D016209:Interleukin-8 / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008969:Molecular Sequence Data; D009000:Monocytes / Q000276:immunology / Q000378:metabolism*; D010835:Phytohemagglutinins / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D018932:Chemokine CCL2; D002630:Chemotactic Factors; D007375:Interleukin-1; D016209:Interleukin-8; D008070:Lipopolysaccharides; D010835:Phytohemagglutinins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha