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[Aggregation of macrophages by a human lymphokine (MAgF). Role of the eicosanoid system]
Abstract:
Peritoneal exudate cells aggregate when exposed to the lymphokine Macrophage Aggregating Factor (MAgF). The role of prostaglandins in the aggregation of these cells has been investigated with a quantitative assay. Results are discussed in the context of the mode of action of the migration inhibiting factor (MIF) and of the other non immune aggregating stimuli such as C5a and fMLP. Prostaglandins E1, E2, and F2 alpha alone did not cause aggregation of macrophages but partially inhibited the MAgF aggregation of macrophages and this effect was not different from the one obtained with MAgF. MAgF, calcium ionophore A23187 and arachidonic acid induced aggregation were blocked by 5, 8, 11, 14-eicosatetraynoic acid, an inhibitor of arachidonic acid metabolism, by indomethacin (10(-4), 10(-6) M) by corticosteroids (dexamethazone, methylprednisolone, hydrocortisone) but not by aspirin (10(-2), 10(-4) M) nor by phenylbutazone (10(-4), 10(-5) M). These results suggest a causal relationship between MAgF induced macrophage aggregation and that due to other stimuli with respect to the derivatives of arachidonic acid. The lipoxygenase pathways metabolites stimulate aggregation whereas the cyclo-oxygenase pathways metabolites inhibit it.
Insights
Macrophage Aggregating Factor (MAgF) triggers cell aggregation, with prostaglandins playing a dual role. Cyclo-oxygenase metabolites inhibit aggregation, while lipoxygenase metabolites stimulate it, suggesting a link between MAgF and arachidonic acid pathways.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Context:
- Macrophage Aggregating Factor (MAgF) induces peritoneal exudate cell aggregation.
- Investigating the role of prostaglandins in macrophage aggregation.
- Comparing MAgF-induced aggregation with other stimuli like C5a and fMLP.
Purpose:
- To elucidate the role of prostaglandins in MAgF-induced macrophage aggregation.
- To understand the involvement of arachidonic acid metabolism in macrophage aggregation.
- To differentiate the effects of lipoxygenase and cyclo-oxygenase metabolites on macrophage aggregation.
Summary:
- Prostaglandins E1, E2, and F2 alpha did not induce aggregation but partially inhibited MAgF-induced aggregation.
- MAgF, calcium ionophore A23187, and arachidonic acid-induced aggregation were blocked by inhibitors of arachidonic acid metabolism (eicosatetraynoic acid, indomethacin) and corticosteroids.
- Aspirin and phenylbutazone did not inhibit the aggregation, suggesting specific pathways are involved.
Impact:
- Suggests a causal relationship between MAgF-induced aggregation and other stimuli concerning arachidonic acid derivatives.
- Highlights that lipoxygenase pathway metabolites stimulate macrophage aggregation, while cyclo-oxygenase pathway metabolites inhibit it.
- Provides insights into the molecular mechanisms regulating macrophage aggregation and inflammatory responses.