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Secretion of monocyte chemoattractant protein-1 (MCP-1) by human mononuclear phagocytes
E J Leonard1, A Skeel, T Yoshimura
1Immunopathology Section, National Cancer Institute, Frederick, Maryland.
Abstract:
Concentrations of MCP-1 and NAP-1 in culture fluids of human leukocytes were measured by sandwich ELISA. PPD caused PBMC's from tuberculin-sensitive subjects to secrete MCP-1 and NAP-1. PPD did not stimulate secretion by cells from a tuberculin-negative subject. Since the amounts secreted were more than could be produced by the few PPD-sensitized lymphocytes in the culture, we postulate that other cells were stimulated to secrete these chemoattractants. This study evaluated secretory capacity of one of the cell types in the PBMC culture. Unstimulated monocytes did not secrete MCP-1 or NAP-1. In order of increasing effect, IL-2 + IFN gamma, IL-1 alpha, and LPS caused monocyte secretion of MCP-1. The rank order for NAP-1 secretion was the same. TNF alpha did not cause secretion of MCP-1, but caused about the same amount of NAP-1 secretion as IL-2 + IFN gamma. Composition of the culture medium was especially critical for LPS-induced secretion of MCP-1, which was greatly enhanced by FCS and by Iscove's DMEM compared to RPMI 1640. IL-4 inhibited LPS-induced secretion of both MCP-1 and NAP-1. Secretory patterns were also a function of mononuclear phagocyte phenotype. LPS-induced secretion of MCP-1 was much greater for monocytes cultured several days in CSF-1 than for freshly isolated monocytes. LPS stimulation of bronchoalveolar macrophages caused NAP-1 secretion, but no secretion of MCP-1 above a relatively low baseline level.
Insights
Tuberculin-purified protein derivative (PPD) stimulates monocytes to secrete MCP-1 and NAP-1, key chemokines in immune responses. This study details factors influencing monocyte secretion of these proteins, crucial for understanding cellular communication in immunity.
Area of Science:
- Immunology
- Cell Biology
Background:
- Monocytes are crucial immune cells involved in inflammatory and immune responses.
- Chemokines like MCP-1 and NAP-1 play vital roles in leukocyte recruitment and immune regulation.
Purpose of the Study:
- To investigate the secretory capacity of monocytes for MCP-1 and NAP-1.
- To identify stimuli and conditions that induce monocyte secretion of these chemokines.
Main Methods:
- Sandwich ELISA was used to measure MCP-1 and NAP-1 concentrations in culture fluids.
- Peripheral blood mononuclear cells (PBMCs) from tuberculin-sensitive and non-sensitive subjects were stimulated with PPD.
- Monocytes were stimulated with various cytokines (IL-2, IFN-gamma, IL-1 alpha, TNF alpha) and lipopolysaccharide (LPS).
Main Results:
- PPD stimulated MCP-1 and NAP-1 secretion from PBMCs of tuberculin-sensitive individuals.
- Unstimulated monocytes did not secrete MCP-1 or NAP-1.
- IL-2 + IFN-gamma, IL-1 alpha, and LPS induced monocyte secretion of both chemokines.
- Culture medium composition (FCS, Iscove's DMEM) significantly enhanced LPS-induced MCP-1 secretion.
- IL-4 inhibited LPS-induced MCP-1 and NAP-1 secretion.
- Monocytes cultured in CSF-1 showed greater LPS-induced MCP-1 secretion than freshly isolated monocytes.
- Bronchoalveolar macrophages secreted NAP-1 but not MCP-1 in response to LPS.
Conclusions:
- Monocytes are a significant source of MCP-1 and NAP-1, particularly when stimulated.
- The secretion of these chemokines by monocytes is influenced by specific cytokines, LPS, and culture conditions.
- Mononuclear phagocyte phenotype affects chemokine secretion patterns.