Structure and Function of Eosinophils: Topic 1 Flashcards
how did eosinophils get their name?
WBC that has big orange-red cytoplasmic granules that stain strongly with eosin (the red part of the wright-giemsa stain)
the granules actually love (“-phil”) the eosin dye!
how much of the total WBC count are eosinophils?
1-6%
what kind of WBC is a eosinophil?
granulocyte
has specific granules!
regular granules that are present in most WBC are called azurophilic granules and they’re small and purple
specific granules are only present in granulocytes
What are three cell types that comprise granulocytes?
Eosinophils, neutrophils, and basophils
what is the structure of an eosinophil?
larger than other granulocytes (12-17 μm)
bilobed nucleus held together by a thin strand of chromatin
condensed, mature, dark chromatin (purple)
what does the cytoplasm of an eosinophil contain?
golgi apparatus and mitochondria
no other organelles
what is inside the specific granules of eosinophils?
arginine
arginine gives the granules the orange-red color
what kind of granules do eosinophils have?
Eosinophils contain specific (eosinophilic) granules, which are large and orange-red
azurophilic granules, which are small and purple.
what proteins are inside the specific granules of eosinophils?
major basic protein and eosinophilic cationic protein
they actually bore holes in parasitic worms, making it easier for reactive oxygen compounds to enter and kill the parasite
what is the function of azurophilic granules in eosinophils?
they function as lysosomes
they contain hydrolytic enzymes and peroxidase, which help kill parasites and hydrolyze antigen-antibody complexes
what are the functions of eosinophils?
- modulate acute hypersensitivity reactions
- defend against parasitic infections
- defend against intracellular bacteria
what role do eosinophils play in allergic diseases?
eosinophils participate in the underlying mechanisms of allergic diseases
help keep inflammatory and immune reactions in check
chemical mediators like leukotrienes and histamine can damage host tissues if they hang around longer than they should –> eosinophils help degrade these mediators and bring immune responses to a proper close
ex. asthma and allergic rhinitis
how do eosinophils fight parasites?
When parasites attack the body, eosinophils respond to chemoattractants and other signals leading them to the site of infection
they are attracted to these places by substances like histamine, leukotrienes, and eosinophil chemotactic factor, which are released by mast cells, basophils, and neutrophils
eosinophils then go to connective tissue beneath the epithelial lining of the respiratory and gastrointestinal tract to carry out their special functions
what is diapedesis?
to get out into tissues and start working, eosinophils first have to get out of blood vessels
they do this by a process called diapedesis, which involves sticking to the endothelial surface, rolling along the endothelial cell surface and coming to a stop, and then squeezing out of the vessel between endothelial cells
what do eosinophils do once they’re at the infection site?
At the infection site, eosinophils become activated and secrete cytokines, degranulate to release cytotoxic chemicals, and phagocytose debris—all of which help to kill parasites
