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CELLULAR COMPONENTS OF INFLAMMATION
LEUKOCYTES: the principal cellular mediators of inflammation, part of the innate immune system.
Under the microscope, inflammation is characterized by the accumulation of leukocytes in the affected tissue due to migration of circulating leukocytes out of the vasculature, a process which is actively mediated and precisely controlled by leukocytes, the cytokines they produce, and the vascular endothelium.
ENDOTHELIAL CELLS regulate leukocyte emigration from the blood into inflamed tissue and
PLATELETS: along with mast cells produce early phase mediators.
LYMPHOCYTES: involved in the specific immune responses.
PHAGOCYTOSIS: consumption of foreigners by white blood cells (WBCs) that are capable of engulfing/absorbing bacteria and other small cells and particles. Simply, it is the process by which phagocytes ingest harmful particles or dead or dying cells.
In inflammation, phagocytes have different roles:
- Margination is the accumulation and adhesion of white blood cells to the endothelial cells of blood vessel walls at the site of injury in the beginning stages of inflammation. Leukocyte-endothelial adhesion requires interactions between leukocytes and endothelial cells, involving multiple steps.
- Diapedesis (AKA extravasation): the movement of white blood cells out of the circulatory system and towards the site of injury.
- Exudation: the oozing of white blood cells into the inflamed tissue.
As cellular components of inflammation, the phagocytes, are polymorphonuclear neutrophils (PMNs), monocytes and macrophages, and eosinophils (primarily in the GI tract).
These are the "professional" phagocytes, (essential for performing phagocytosis).
POLYMORPHONUCLEAR NEUTROPHILS (PMNs, or granulocytes) are a type of white blood cells that have granules in their cytoplasm and have varying nucleic shape.
Granulocytes are predominate in the early inflammatory response and are responsible for first response to inflammation and attempt to either destroy, granulate or trap pathogens via degranulation.
MONOCYTES are young macrophages (macrophages that have not yet matured): large white blood cells with a simple oval nucleus and clear, gray cytoplasm, responsible for replenishing ranks of macrophages.
*Macrophages * are simply monocytes that have traveled to the tissue to work; there are some differences in the type of proteins they express as well.
EOSINOPHILS: a type of polymorphonuclear leukocyte that become active to fight off parasites and destroy antigen-antibody complexes.