How does the immune system act to microbes?

White blood cells (WBCs) recognize bacteria as foreign, often through receptors on their surface called Toll-like receptors (TLRs). WBCs then phagocytose (swallow) the bacteria. Usually the bacteria is destroyed by digestive enzymes and acid within the WBC, but some pathogenic bacteria escape the acid and enzymes or they tolerate it and eventually escape. Other pathogenic bacteria have negatively charged capsules that prevent phagocytosis in the first place. Some WBCs also produce chemicals, including antibodies, that directly or indirectly kill microbes.