Aggregated bovine IgG inhibits mannose receptor expression of murine bone marrow-derived macrophages via activation.

Authors:
S Schreiber, W F Stenson, R P MacDermott, J C Chappel, S L Teitelbaum, S L Perkins
Year of publication:
1991
Volume:
147
Issue:
4
Issn:
0022-1767
Journal title abbreviated:
J IMMUNOL
Journal title long:
The journal of immunology
Impact factor:
4.985
Abstract: 
We previously described the presence of an inhibitory protein contained in the 20 to 40% (NH4)2SO4 precipitable fraction of FCS that down-regulates expression of mannose receptors on bone marrow-derived macrophages. We now identify aggregated bovine IgG as the main inhibitory component. Heat-aggregated bovine IgG was capable of down-regulating expression of the macrophage mannose receptor in a dose-dependent manner without inducing changes in ligand affinity whereas neither F(ab'')2 fragments nor nonaggregated IgG displayed any inhibitory effect. Depleting of IgG from heat inactivated FCS by protein G affinity chromatography completely removes the inhibitory activity. Moreover, readdition of the Ig eluate from the protein G chromatography column restored inhibition in a dose-dependent manner. Macrophages were able to clear exogenously added aggregated bovine IgG, thus leading to loss of inhibitory activity in macrophage-conditioned media as compared to sham-conditioned media containing aggregated IgG. These results indicate that aggregated IgG down-regulates mannose receptor expression by macrophage activation via interaction with Fc-gamma R.