Phagocytosis Flashcards
What is phagocytosis?
Effector function part of the immune response but also a mechanism that connects innate and adaptive immunity
Give the 5 roles of phagocytosis
- destruction of pathogen
- activation of genes
- antigen presentation
- cell recruitment
- elimination and disposal of dead, apoptotic and damaged cells
How do phagocytes destroy pathogens?
Respiratory burst
What does the activation of genes in phagocytosis lead to?
Cytokine and chemokine release
Where do blood monocytes originate from?
Monocytes
What do blood monocytes differentiate into?
Specialised tissue-specific macrophages
What are blood monocytes efficient at?
Detecting and killing microbes
How do blood monocytes kick start immune responses?
Secretion of inflammatory factors (cytokines)
What is an effector cell?
A cell that carries out a function
What is the most abundant white blood cell?
Neutrophil
What are neutrophils?
Polymorphonuclear leukocytes
What is the life span of neutrophils?
8-10 hrs in blood and 4-5 days in tissue
What enzymes do neutrophils produce (3)?
Lysozyme, collagenase and elastase
What is netosis?
Essentially, cells lyse and release their genomic DNA
Genomic DNA in solution is sticky and this will cover bacteria and prevent it colonising
What do dendritic cells do?
Capture microbes and antigens
Which type of myeloid cell links the innate and adaptive immune responses?
Dendritic cells
What are the four steps of phagocytosis?
Chemotaxis
Recognition and attachment to microbe/dead cells
Engulfment
Killing/digestion of i
What is chemotaxis?
Movement of cells towards the site of infection
What is chemotaxis guided by?
Chemoattractants
What are chemoattractants released by?
Bacteria and inflammatory cells
What does the recognition and attachment of phagocytes require?
React to invading pathogens and a regulated reaction to bodies own tissues
What does DAMP stand for?
Damage associated molecular patterns
Give the 5 types of PRRs
Toll like receptors C-type lectin receptors NOD-like receptors RIG-like helicase receptors Scavenger receptors
Where do you find toll like receptors?
Plasma membrane and endosomal membrane
Give an example of c-type lectin receptors
Mannose
Where do NOD-like receptors reside?
Free proteins in the cytoplasm
What are RIG-like helicase receptors?
Cytosolic receptors for viral dsRNA
What do TLRs do?
Stimulate the production of inflammatory Cytokines
What does opsonisation factilitate?
Phagocytosis
How are protrusions formed on the cell membrane?
Actin cytoskeleton rearrangement
What is a phagolysosome and when is it formed?
It is when a lysosome binds to the phagosome in the breakdown of a pathogen
What are the four things in lysosomes?
Proteolyitc enzymes
Lysozyme
Lactoferrin
Defending
What do proteolytic enzymes do?
Degrade microbes
What do lysozymes do?
Break bacterial walls
What does lactoferrin do?
Binds with iron so there’s not enough left for bacteria
What do defensins do?
Destroy bacterial walls
What are the four ways in which microbes evade phagocytes?
Block phagocyte attachment
Block engulfment
Block destruction
Killing of phagocytes
Give an example of a microbe that blocks phagocyte attachment
Streptococcus pneumoniae
Give an example of a microbe that blocks engulfment
Yersinia
Give an example of a microbe that blocks destruction
Salmonella
Give an example of a microbe that kills phagocytes
Staphylococcus aureus
What can phagocytosis be used for that isn’t killing microbes?
Damaged or dying cells and apoptosis
What happens when a phagocyte takes up an apoptotic cell?
Change to a pro-healing phenotype
Secrete pro healing cytokines
Present self antigens
