Enhanced binding and degradation of the C1q subcomponent of complement by thioglycollate-stimulated guinea pig peritoneal macrophages.

Expression of C1q receptors on the plasma membrane of thioglycollate-stimulated guinea pig peritoneal exudate macrophages increased 1.54 times as compared to unstimulated controls. A Scatchard plot of the binding of 125I-C1q to the cells revealed that the binding is a result of an increase in the number of receptors and not to an increased affinity of the receptors. Thioglycollate-activated macrophages were found to be 1.6 times more active than nonactivated macrophages in the binding of 125I-C1q at 4 degrees C. The enhanced binding of 125I-C1q by activated peritoneal macrophages was reflected in an increase in the amount of 125I-C1q degraded by these cells as compared to resident peritoneal macrophages. This suggests that stimulation of phagocytic cells leads to an increase in the expression of C1q receptors and to a concomitant increase in the uptake and degradation of C1q.