Interleukin-4 increases phagocytosis of necrotic cells by macrophages through scavenger receptor CD36

Objective: Interleukin-4 (IL-4) signalling pathways regulate the activity of macrophages, enhance their proteolytic capacity and drive resolution of inflammation during tissue repair. The aim of this study was to examine whether IL-4 can enhance phagocytosis of necrotic cells and elucidate the molecular mechanisms. Methods: Phagocytosis of necrotic thymocytes by RAW264.7 cells, a macrophage cell line, with or without IL-4 treatment, was determined by flow cytometry. Protein expression was determined by western blot analysis. Results: The phagocytosis index was significantly increased by IL-4 (10 ng/mL). IL-4-enhanced phagocytosis was mediated by upregulation of scavenger receptor CD36. STAT6 activation is required for IL-4-mediated phagocytosis. Conclusions: Interleukin-4 can accelerate cell debris clearance by stimulating expression of CD36, which requires downstream STAT6 activation. Its beneficial effects on driving tissue repair and regeneration should be explored in future studies.