The image to the right shows the process of phagocytosis in more detail. Pathogens release chemicals and present antigens on their surface, which can be detected by phagocytes that travel through the bloodstream. The phagocyte migrates towards the pathogen and engulfs the microorganism by infolding its own membrane. This area pinches off the membrane within the phagocyte, forming a vacuole. The phagocyte's cytoplasm is rich in lysosomes, which contain digestive enzymes. Lysosomes can fuse with the pathogen-filled vacuole and release the digestive enzymes into it. This allows the pathogen to be broken down by digesting proteins and DNA. The products of digestion are then absorbed by the phagocyte.

Interestingly, once this process has been completed, the phagocyte secretes cytokines - these chemicals attract even more phagocytes to the infected area to build a larger immune response. As the dead bacteria and phagocytes build up in the area, pus forms.