Lecture 3 Flashcards
Identify the following cell types.
- Eosinophil.
- Neutrophil.
- Basophil.
Define “acute inflammation.”
Accumulation of neutrophils in the tissues.
What is pus composed of?
Dead and dying neutrophils.
True or False: Neutrophils have uncondensed chromatin, so they can readily regenerate.
FALSE
Neutrophils have condensed chromatin. They are short-lived, end-stage cells.
What might you find in a neutrophil’s vesicles?
Proteolytic enzymes
Bacteriocides
Glycogen
How long will a neutrophil live in normal (uninflamed) tissue?
1-2 days.
How long does a neutrophil normally circulate in the blood stream?
8-10 hours.
True or False: Neutrophils require specific antigens in order to attack pathogens.
FALSE
Neutrophils are part of the innate immune system and do not respond to specific antigens.
Neutrophils store glycogen, which is unusual amongst leukocytes. What do they use it for?
Anaerobic respiration.
Useful for penetrating damaged tissue where the oxygen supply may be cut off.
Neutrophils are not perfectly circular, but have a lot of extra membrane. Why is this?
Phagocytosis.
Motility.
Name the four major receptor types on the neutrophil surface.
Cell adhesion molecules.
Antibody receptor (FcR).
Complement receptors.
Cytokine (inflammatory mediator) receptors.
What is the term for a neutrophil slowly rolling along a blood vessel?
Margination.
Where does neutrophil margination occur?
Post-capillary venules.
What is the term for an acute neutrophilia in the blood induced by fear, epinephrine, or glucocoritcoids?
Stress leukogram.
How do anti-inflammatories affect neutrophils?
They disrupt margination, preventing neutrophils from migrating to target tissues.
Which endothelial molecules are responsible for neutrophil rolling?
Selectins.
Which endothelial molecules are responsible for neutrophil sticking (i.e. cause the neutrophil to stop rolling)?
Integrins.
Define diapedesis.
The passage of a cell through the intact endothelial layer to reach a target tissue.
In neutrophils, diapedesis occurs after the neutrophil has encountered integrin molecules.
Define chemotaxis.
The movement of a cell in response to chemical stimuli.
Neutrophils rely on chemotaxis to locate bacteria in the tissues.
Define opsonization.
When a pathogen is marked and prepared for phagocytosis.
Opsonin molecules may include:
Antibody
Complement molecules
Some acute phase proteins
What is the name of the pictured process?
Diapedesis.
This is a neutrophil squeezing in between endothelial cells.
True or False: A neutrophil will not bind to anything more hydrophilic than itself.
TRUE
Neutrophils can bind to objects that are more hydrophobic than themselves.
What is the term for an engulfed membrane-bound vesicle containing a microbe?
Phagosome.
What is the term for a phagosome that has fused with a lysosome?
Phagolysosome.
What is required for a neutrophil to bind to a microbe?
If the microbe’s membrane is more hydrophobic than the neutrophil’s, the neutrophil can bind.
Otherwise, the microbe must be opsonized.
How does a bacterial capsule protect a bacterium from neutrophils?
The hydrophilic capsule prevents phagocytosis.
Mycobacteria are effective intracellular pathogens. How do they enter the cell? How do they survive once inside?
Mycobacteria have hydrophobic capsules, facilitating their uptake by neutrophils. Once inside, they resist being killed in the phagosome.
Name the three killing methods used by a neutrophil.
- Enzymes from granules.
- Oxidative metabolism (respiratory burst).
- Defensins.
True or False: Defensins are effective against bacterial capsules.
FALSE
Defensins are only effective against membranes.
How do defensins work?
Have hyrophobic and hydrophilic ends. The hydrophobic ends insert into the membrane. Multiple molecules form a pore in the membrane, causing cellular lysis.
Why is lactoferrin effective against bacteria?
Bacteria require iron for growth. Lactoferrin sequesters iron through chelation, preventing bacterial growth.
Describe the pH changes within the phagosome.
- Killing phase - pH is basic, allowing defensins to function.
- Digestion phase - pH is acidic, allowing hydrolases to function.
What is the most potent killing mechanism of a neutrophil?
Respiratory burst.
True or False: Neutrophils can perform respiratory burst under anaerobic conditions.
FALSE
Oxygen is required to create reactive oxygen intermediates.
What factors can upregulate neutrophil activity?
Innate defense cytokines
T helper cytokines
What is a NET?
Neutrophil Extracellular Trap
If a neutrophil cannot phagocytose a pathogen, it undergoes netosis, whereby it explodes and casts a net of DNA and histones.
How will endothelial cells respond to “danger signals” from the tissues (i.e. PAMPs and DAMPs)?
Upregulate integrins to facilitate neutrophil movement to the target tissues.
What is the primary function of eosinophils?
Defense against multicellular parasitic invasion (e.g. helminths).
What color do an eosinophil’s granules stain?
Pink
True or False: Eosinophils rely on phagocytosis to kill pathogens.
FALSE
An eosinophil’s targets are too large to be phagocytosed. Damaging products are released extracellularly.
True or False: An eosinophil can perform diapedesis and chemotaxis much like a neutrophil.
TRUE
What factors can increase eosinophil activity?
Cytokines from T cells and macrophages.
What factors can decrease eosinophil activity?
Stress and glucocorticoids
What factors can decrease neutrophil activity?
Stress, glucocorticoids
Some viral infections
Bacterial virulence factors
Prepartrurient period
Neonate (less efficient neutrophil function. Improves over first week of life).
