Neutrophilic leukocyte structure and function in domestic animals.

Differences in neutrophil morphology between various species of domestic animals are evident when morphometric techniques are used. Morphometric analysis can be coupled with functional assays of degranulation to demonstrate changes in granule volume after neutrophil activation (Bertram and Jensen, 1984). Morphometric and functional analysis of the neutrophil can also be used to evaluate the response of neutrophils to infectious agents (Coignoul et al., 1984a). Comparison of these assays between animal species may provide insight into the susceptibility of animals to various microbial pathogens. The enzyme content of neutrophil granules has been extensively studied, but the process of enzyme release from granules is poorly understood. Granule contents are assumed to be released in an "all or none" fashion. The presence of unique forms of granules (granules with a flocculent matrix) seen in degranulating neutrophils suggests that partial granule-content release as well as total granule-content release may be controlled by similar processes. If a selective process of granule enzyme release occurs, a more refined control of degranulation may exist than has been previously believed. Functions of neutrophilic leukocytes include phagocytosis, killing, and digestion of microbes which invade the host. The neutrophil is also able to increase vascular permeability, help or suppress some T and B lymphocyte responses, and modify some phases of the inflammatory process. Research into the role of neutrophils in killing tumor cells has demonstrated the potential beneficial effects of neutrophil-mediated tissue-damaging mechanisms.