Macrophages are pattern recognition receptors (PPR's) which are involved in the innate immune system of organisms, these phagocytic white blood cells are the first to respond to infection. They also play a role in inflammation of tissues. When activated, they become antigen presenting cells as well as producing chemokines and cytokines. They work by engulfing pathogens detected by the immune system and engulfing them. The newly engulfed pathogen is then bound to a phagosome and lysosome which release enzymes and toxic chemicals that digest the pathogen.