Macrophage: the name means "Big Eater".
Together with its cousins (monocytes, histiocytes, dendritic cells, Kupffer cells, microglia, osteoclasts), it plays multiple roles in inflammation and repair.
It functions as a scavenger, gobbling germs and dying cells, acting as the first line of defence (innate immunity) against invading microbes and rogue cancer cells. It processes and presents the information gathered in the scavenging to T cells (the brainy ones of the immune system), thereby activating the adaptive immune response. It may thereafter be directed by the latter to spearhead a concerted assault on the enemy, like a tank brigade punching through enemy lines. When all is done and calm, it morphs into a peacekeeping role to repair and rebuild.
It's a scary burly figure you wouldn't want to meet in a dark alley if you're a bug. Meet your doom.
Apparently, protein fragments released from dying neutrophils (foot soldiers of the immune system) can continue to kill bacteria as well as calm down the macrophages.
Research into peptides like alpha-defensin may produce new drugs which can help us fight infections as well as protect us from collateral damage from a runaway immune response.