Extravasation of Neutrophils (Kan 2024)
Neutrofil, type hvide blodlegemer (leukocyt), som er histologisk karakteriseret ved dens evne til at blive farvet af neutrale farvestoffer og funktionelt af dens rolle i formidling af immunrespons mod infektiøse mikroorganismer. Neutrofile udgør sammen med eosinofiler og basofiler en gruppe hvide blodlegemer kendt som granulocytter. Granulaterne af neutrofiler farver typisk lyserød eller lilla-blå efter behandling med et farvestof. Cirka 50 til 80 procent af alle de hvide blodlegemer, der forekommer i den menneskelige krop, er neutrofiler.
blod: Neutrofiler
Neutrofilerne er temmelig ensartede i størrelse med en diameter mellem 12 og 15 um. Kernen består af to til fem lobber, der er forbundet
Neutrofilerne er temmelig ensartede i størrelse med en diameter mellem 9 og 15 mikrometer. Kernen består af to til fem fliser, der er forbundet med hårlignende filamenter. Neutrofiler bevæger sig med ameboid bevægelse. De forlænger lange fremspring kaldet pseudopodium, hvor deres granulater flyder i; denne handling efterfølges af sammentrækning af filamenter, der er baseret i cytoplasmaet, som trækker kernen og bagsiden af cellen fremad. På denne måde går neutrofile hurtigt frem langs en overflade. Knoglemarven fra en normal voksen producerer ca. 100 milliarder neutrofiler dagligt. Det tager cirka en uge at danne en moden neutrofil fra en precursorcelle i margen; endnu en gang i blodet lever de modne celler kun et par timer eller måske lidt længere efter migrering til vævene. For at beskytte mod hurtig udtømning af den kortvarige neutrofil (f.eks.under infektion) har knoglemarven et stort antal af dem i reserve for at blive mobiliseret som reaktion på betændelse eller infektion.
Within the body the neutrophils migrate to areas of infection or tissue injury. The force of attraction that determines the direction in which neutrophils will move is known as chemotaxis and is attributed to substances liberated at sites of tissue damage. Of the many neutrophils circulating outside the bone marrow, half are in the tissues and half are in the blood vessels; of those in the blood vessels, half are within the mainstream of rapidly circulating blood and the other half move slowly along the inner walls of the blood vessels (marginal pool), ready to enter tissues on receiving a chemotactic signal from them.
Neutrophils are actively phagocytic; they engulf bacteria and other microorganisms and microscopic particles. The granules of the neutrophil are microscopic packets of potent enzymes capable of digesting many types of cellular materials. When a bacterium is engulfed by a neutrophil, it is encased in a vacuole lined by the invaginated membrane. The granules discharge their contents into the vacuole containing the organism. As this occurs, the granules of the neutrophil are depleted (degranulation). A metabolic process within the granules produces hydrogen peroxide and a highly active form of oxygen (superoxide), which destroy the ingested bacteria. Final digestion of the invading organism is accomplished by enzymes.
An abnormally high number of neutrophils circulating in the blood is called neutrophilia. This condition is typically associated with acute inflammation, though it may result from chronic myelogenous leukemia, a cancer of the blood-forming tissues. An abnormally low number of neutrophils is called neutropenia. This condition can be caused by various inherited disorders that affect the immune system as well as by a number of acquired diseases, including certain disorders that arise from exposure to harmful chemicals. Neutropenia significantly increases the risk of life-threatening bacterial infection.
