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Relationship of human macrophage agglutination factor to other fibronectins
H P Godfrey1, L S Canfield, M Haak-Frendscho
1Department of Pathology, New York Medical College, Valhalla 10595.
Abstract:
Human macrophage agglutination factor (MAggF) is a lymphokine with a number of biochemical and immunochemical similarities to the fibronectins (FN). The present study was undertaken to define this relationship more exactly. Peripheral blood mononuclear cells (PBMC) and cloned human CD4+T-cell lines synthesized both MAggF and immunoreactive FN de novo following antigen or mitogen activation. MAggF produced under those conditions co-purified with an immunoreactive FN on gelatin-affinity and gel-filtration chromatography. This FN had a consistently slightly smaller relative molecular mass than plasma FN on both immunoblotting and gel filtration. Purified human MAggF was extremely active: it agglutinated human monocytes at fM concentrations and was up to 2,000,000 times more active in agglutinating mononuclear phagocytes than other purified FN. The action of MAggF on monocytes was dependent on at least two antigenically distinct cell-surface FN receptors. We suggest that the extreme activity of MAggF is a result of co-operative interactions between FN domains on the MAggF molecules and multiple distinct classes of FN receptors on responding cells.
Insights
Human macrophage agglutination factor (MAggF), a lymphokine similar to fibronectins (FN), potently agglutinates monocytes. This extreme activity is linked to interactions between MAggF and cell-surface FN receptors.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Human macrophage agglutination factor (MAggF) shares similarities with fibronectins (FN).
- The precise relationship between MAggF and FN requires further definition.
Purpose of the Study:
- To precisely define the relationship between MAggF and fibronectins (FN).
- To investigate the mechanism behind MAggF's potent monocyte agglutination activity.
Main Methods:
- Peripheral blood mononuclear cells (PBMC) and CD4+T-cell lines were activated.
- MAggF and FN were purified using gelatin-affinity and gel-filtration chromatography.
- Immunoblotting and gel filtration were used to determine molecular mass.
- Monocyte agglutination assays were performed.
Main Results:
- MAggF and immunoreactive FN were co-purified from activated PBMC and T-cell lines.
- MAggF exhibited a slightly smaller molecular mass than plasma FN.
- Purified MAggF agglutinated human monocytes at femtomolar concentrations, significantly exceeding the activity of other FN.
- MAggF's action on monocytes involved at least two distinct cell-surface FN receptors.
Conclusions:
- MAggF is closely related to fibronectins.
- The high potency of MAggF in agglutinating monocytes is attributed to cooperative interactions between its FN domains and multiple cell-surface FN receptors.