Neutrophils

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Flashcards by , created over 5 years ago

From the 23-09-13 Immunology and Disease lecture.

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sophietevans
Created by sophietevans over 5 years ago
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Question Answer
Why are neutrophils classified as granulocytes along with eosinophils and basophils? Neutrophils (phagocytic), eosinophils and basophils are all classified as granulocytes on the basis of cellular morphology and cytoplasmic-staining characteristics. They appear granular on staining as a result of the presence of granules which they use in their immune responses.
How do neutrophils appear histologically? Neutrophils have multi-lobed (it is often called polymorphonuclear) nuclei and a granulated cytoplasm that stains with both acid and basic dyes.
Here is a picture of a neutrophil. neutrophil.png (image/png)
How long do neutrophils circulate in the blood before entering the tissues? They are produced by the myeloid route of haematopoiesis in the bone marrow and are released into the peripheral blood, where they circulate for 7 to 10 hours before migrating into the tissues, where they have a life span of only a few days.
In infections in which neutrophils respond, what proportion of circulating leukocytes do they constitute? Neutrophils are produced and released from the bone marrow in higher numbers than usual (50-70% of circulating leukocytes) in response to many different infections.
At what stage in an immune response do neutrophils arrive at a site of inflammation? They are generally the first to arrive at a site of inflammation. This leukocytosis (transient increase) is a medical indication of infection.
What are the three basic steps involved in neutrophil extravasation? Extravasation: The neutrophil adheres to the vascular endothelium. The neutrophil penetrates the gap between adjacent endothelial cells lining the vessel wall using pseudopodia. The neutrophil penetrates the vascular basement membrane, moving out into the tissue spaces.
What attracts neutrophils to a site of inflammation? Inflammatory mediators act as chemotactic factors that promote accumulation of neutrophils at an inflammatory site. These include some of complement components, components of the clotting cascade, and several cytokines secreted by activated TH cells and macrophages.
Neutrophils differ from macrophages in that they have primary and secondary granules. Describe each of these. What do they contain and do? • Primary - these are larger and denser and are a type of lysosome containing peroxidase, lysozyme, and various hydrolytic enzymes. • Secondary - this are smaller and contain collagenase, lactoferrin, and lysozyme. →Both primary and secondary granules fuse with phagosomes, whose contents are then digested and eliminated.