"The various types of granulocytes can be distinguished from one another in a blood smear by the appearance of their nuclei and the contents of their granules, which confer different traits, functions, and staining properties. Neutrophils, also called polymorphonuclear neutrophils (PMNs), have a nucleus with three to five lobes and small, numerous, lilac-colored granules. Each lobe of the nucleus is connected by a thin strand of material to the other lobes. Eosinophils have fewer lobes in the nucleus, typically two to three, and larger granules that stain reddish-orange. Basophils have a two-lobed nucleus and large granules that stain dark blue or purple. Neutrophils are frequently involved in the elimination and destruction of extracellular bacteria. They can migrate through the walls of blood vessels to areas of bacterial infection and tissue damage, where they seek out and kill infectious bacteria. PMN granules contain defensins and hydrolytic enzymes that help them destroy bacteria through phagocytosis. When many neutrophils are brought into an infected area, they can be stimulated to release toxic molecules into the surrounding tissue to better clear infectious agents; this is called degranulation. Neutrophils also use neutrophil extracellular traps (NETs), which are extruded meshes of chromatin closely associated with antimicrobial granule proteins and components. Chromatin is DNA with associated proteins, usually histone proteins, around which DNA wraps for organization and packing within a cell. By creating and releasing a mesh or lattice-like structure of chromatin coupled with antimicrobial proteins, neutrophils can mount a concentrated and efficient attack against nearby pathogens. Proteins frequently associated with NETs include lactoferrin, gelatinase, cathepsin G, and myeloperoxidase. The toxic proteins in NETs may kill some of the body’s own cells along with invading pathogens, although this collateral damage can be repaired after the danger of infection has been eliminated. As neutrophils fight an infection, an accumulation of leukocytes, cellular debris, and bacteria can be observed at the infection site. This buildup is called pus, also known as purulent or suppurative discharge or drainage. Pus indicates that immune defenses have been activated against an infection, but artificially inducing pus formation does not promote recovery. Eosinophils protect against protozoa and helminths and also play a role in allergic reactions. Their granules, which readily absorb the acidic reddish dye eosin, contain histamine, degradative enzymes, and major basic protein (MBP). MBP binds to the surface carbohydrates of parasites, and this binding is associated with disruption of the cell membrane and membrane permeability. Basophils have cytoplasmic granules of varied size and are named for their ability to absorb the basic dye methylene blue. Their stimulation and degranulation can result from multiple triggering events. Activated complement fragments C3a and C5a act as anaphylatoxins by inducing degranulation of basophils and inflammatory responses. Basophils are important in allergic reactions and other inflammatory responses. Histamine is one of the most abundant components of basophil granules and is released with other chemical factors when the basophil is stimulated. These chemicals can be chemotactic and can help open gaps between cells in blood vessels. Other mechanisms for basophil triggering require the assistance of antibodies. Hematopoiesis also gives rise to mast cells, which appear to be derived from the same common myeloid progenitor cell as neutrophils, eosinophils, and basophils. Mast cells are functionally similar to basophils, contain many of the same granule components such as histamine, and play similar roles in allergic responses and other inflammatory reactions. Unlike basophils, mast cells leave the circulating blood and are most frequently found residing in tissues. They are often associated with blood vessels and nerves or found close to surfaces that interface with the external environment, such as the skin and mucous membranes."