A brief exposure of murine peritoneal inflammatory macrophages to plasma histidine-rich glycoprotein (HRG; 77,000-81,000 MW) for 1-2 hr increased Fcγ receptor (FcγR) expression and phagocytic function in these cells. However, a continual culture of the cells without the presence of HRG for the next 18- 48 hr resulted in down-regulation of FcγR expression and phagocytic function. Similarly, HRG decreased FcγRII expression in less differentiated human THP-1 monocytic cells during treatment for 18 hr, as determined by cellular ELISA and metabolic labelling. The molecular mechanism by which HRG regulates FcγR expression is unknown. However, at a relatively high concentration (> 1 μg/ml), HRG altered the cellular metabolism by increasing cellular protein synthesis but reducing protein secretion. These observations suggest a likely mechanism for the HRG-mediated reduction of FcγR expression. A degraded HRG (40,000 MW) which possessed an identical N- terminal sequence as that of the native HRG was capable of decreasing macrophage FcγR expression and phagocytosis. The results indicate that the functional domain of HRG responsible for binding to macrophages is localized to the N-terminal half.
|Number of pages||7|
|Publication status||Published - 1994 Jan 1|
All Science Journal Classification (ASJC) codes
- Immunology and Allergy