Slow regeneration of inmune complex binding sites on the macrophage surface after previous digestion with pronase

Peroxidase-antiperoxidase (PAP) binding sites on the rat peritoneal macrophage surface were damaged by pronase digestion and the reappearance of functionally intact receptors was investigated morphologically and spectrophotometrically. Pronase digestion decreased the PAP binding ability of macrophages to about 40% of the original value. Removing the pronase the regeneration of ligand binding was very protracted with only about 60% intact receptors even after 30 min. From these findings we conclude that the recycling of internalized Fc receptors greatly contribute to the replenishment of receptors on the cell surface.