PMNs are phagocytic cells, like macrophages, but do not act as antigen presenting cells, instead are most effective at killing ingested microorganisms. Macrophages are large phagocytic cells, may be motile or localized to a specific tissue. Ingested antigens are processed internally, and then fragments are presented to reactive lymphocytes to stimulate the immune response. They secrete interferon and lysosyme to upregulate inflammatory response. Monocytes are immature macrophages.
Eosinophils are granulocytes which can stain intensely with the dye eosin.
The cytoplasm is filled with granules of basic substances such as histamine. Eosinophils are motile, phagocytic agents against parasites, but are also partly responsible for allergies. Basophils are granulocytes stained by basic dyes such as toluidine blue, carrying IgE receptors. As they mature, they settle into fixed tissue locations and become mast cells. Mast cells are tissue-resident granule containing cells with IgE receptors.