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20 Cards in this Set
- Front
- Back
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Neutrophils comprise roughly 70% of WBCs in circulation. True/False
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True. About 100 billion of these cells are made each day in bone marrow.
Neutrophils live a short time, about 5 days. |
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Are neutrophils considered antigen presenting cells?
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No. They are like professional killers. They are activated as they exit the blood. They are very phagocytic.
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Are neutrophils activated inside blood vessels?
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No. They are fast movers. They can move through the blood at at about 1,000 microns per second.
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What is the ICAM protein?
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This is Intercellular adhesion molecule. This is expressed on the surface of the endothelial cells that line blood vessels.
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What is the SLIG protein?
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This is another adhesion molecule called selectin ligand (SLIG) that is found on the surface of neutrophils.
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Are SLIG and ICAM molecules drawn to each other?
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NO. These 2 adhesion molecules are not known to work directly together.
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if one gets a splinter in the index finger, how will macrophages react to this foreign object?
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Macrophages are activated. They will release cytokines Interleukin 1 and TNF which basically signal that some sort of invasion is about to take place.
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How do endothelial cells react within nearby blood vessels to these substances given off by the macrophages?
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The endothelial cells will express a new protein on their surfaces called Selectin (SEL). This protein is made in about 5 hours.
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What is the function of Selectin?
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Selectin is the adhesion partner for selectin ligand. When selectin is expressed on the endothelial cell surface, it will attract neutrophils as they pass by.
This attraction will only result in the neutrophils slowing down and being drawn closer to the inner surface of the blood vessel. It senses an inflammatory reaction of some kind. |
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What are two inflammatory signals recognized by the neutrophil?
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The complement fragment, C5a and the bacterial wall component, LPS are two signals recognized by the neutrophil.
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What does the neutrophil do when it senses these two signals?
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It sends a new protein termed Integrin (INT) to its surface. Much of this protein is made in advance.
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Will integrin eventually bind to another protein?
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Yes. It willbind to ICAM, which is on the surface of endothelial cells. At this point the neutrophil stops rolling.
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What will then happen once the neutrophil is stopped/
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It will be acted on by molecules called chemoattractants to spread apart the endothelial cells that line blood vessels, and it can now exit into tissues, and go to the site of inflammation.
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List two of these chemoattractants.
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One is C5a of the complement system, and fragments of bacterial proteins called f-met peptides.
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What is f-met protein?
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All bacterial proteins commence with a special initiator amino acid called formyl methionine (f-met) which less than0.01% of human proteins contain. f-met peptides are somewhat unique to bacterial membranes.
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How do neutrophils follow the trail of f met peptides?
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As macrophages ingest bacteria, macrophages release f-met peptides, and the neutrophils that have exited the blood can follow the trail of the f-met peptides to find the inflammatory nidus.
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Does any other substance activate neutrophils as they travel through the tissues/
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Yes. Cytokines such as TNF activate neutrophils as they travel through the tissues, ready to destroy.l
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In humans, approximately how many endothelial cells exist?
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About 100 billion.
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The sustained expression of alarm cytokines from macrophages engaged in battle is necessary to upregulate selectin expression. True/False
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True. This insures that more neutrophils will be called upon only when they are really needed.
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Are neutrophils the only blood clls that can exit blood vessels?
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No. Eosinophils and mast cells, which protect against parasites, must exit the blood at sites of parasitic infection.
Also, B cells and T cells must exit the blood and enter lymph nodes where they can be activated. When activated they will be sent to sites of infection. |
