How macrophages use extracellular calreticulin to chase their prey.

Recent findings reveal that macrophages actively control clearance by desialylating target cells via NEU1 and releasing cathepsin-cleaved calreticulin (CALR) to mark them for phagocytosis. This uncovers a dual role for CALR as immune activator or repressor, depending on its form and context, with distinct implications for cancer immunity.