Macrophages are professional phagocytes in innate immune responses. Phagocytic cells such as neutrophils, eosinophils, and mononuclear phagocytes produce ROS when stimulated. Neutrophils are phagocytes, capable of ingesting microorganisms or particles. Neutrophils and other phagocytes use peroxide to kill bacteria. These negatively charged phospholipids are recognized by phagocytes such as macrophages. Neutrophils are much more numerous than the longer-lived monocyte/macrophage phagocytes. All phagocytes, and especially macrophages, exist in degrees of readiness. Teicoplanin is much better at penetrating into leukocytes and phagocytes than vancomycin. IL-15 is secreted by mononuclear phagocytes (and some other cells) following infection by virus(es). The lipid phagocytes are later replaced by a cellular reaction of astrocytes. Fungi are destroyed via oxidative pathways by phagocytes both intracellularly and extracellularly. Certain microorganisms have evolved countermeasures which enable them to evade being destroyed by phagocytes. Oxidative burst in phagocytes is most commonly associated with bacterial killing. The phagocytes move by a method called chemotaxis. This also prevents agglutination (clotting) of phagocytes by antibody when there is no antigen.