Phagocytosis Flashcards
What is phagocytosis defined as?
engulfment/ internalization of materials
What 3 cells is phagocytosis mostly in? = phagocytes
macrophages/ neutrophils/ DC
What are the 5 steps of phagocytosis?
- Bacterium binds to PRRs on pseudopodia
- Bacterium ingested- forming phagosome
- Phagosome fuses with lysosome
- Bacterium killed/ digested low pH
- Digestion products released
What is the main PRR for phagocytosis?
CLRs
Are TLR’s involved in phagocytosis?
no
What PRRs are involved in phagocytosis?
CLRs/ scavenger receptors
What is an example of a CLR for phagocytosis?
Dectin-1
What are 2 examples of Opsonin receptors for phagocytosis?
Complement receptors- CR1/ CR3/ CR4
Immunoglobulin Fc receptors
How are microbes recognized?
by receptors on phagocytes
How do phagocytes recognize microbes?
soluble opsonin protein bound
What is an important part of Opsonin?
mannose-binding lectin serine proteases
How does destruction in phagosomes occur after fusion with lysosomes/ granules?
ROS/ RNS/ antimicrobial proteins. enzyme degredation
What is a common molecule of ROS/ RNS?
Superoxide anion (O2) + Nitric Oxide (NO)
= Peroxynitrate (ONOO)
What form of cell death is induced by TNF binding to TNFR/ NK cells/ T cytotoxic cells?
Apoptosis
What is a form of programmed cell death?
Apoptosis
What form of cell death activation requires NADPH oxidase/ ROS generation?
Neutrophil extracellular traps NETs
What form of cell death involves “filament extension”?
Neutrophil extracellular traps = NETs
What form of cell death is induced by inflammasome activation?
Pyroptosis
What form of cell death eliminates infected macrophages allowing the release of IL-1B/ IL-18 = proinflammatory cytokines?
Pyroptosis
What are 2 early components of inflammation?
increased vascular permeability
recruitment of neutrophils from blood to damage site
What are the later stages of inflammation called?
Acute phase responses = APRs
What are APRs induced by?
proinflammatory cytokines = IL-1/ TNF-a/ IL-6
What does APR include?
opsonin, increased synthesis of antimicrobial proteins by the liver
What antimicrobial proteins are synthesized with acute phase responses APR of inflammation?
mannose-binding lectin/ c-reactive protein/ complement proteins
Why are NK cells lymphocytes with innate immune functions?
can directly kill pathogens
What cells can NK cells target?
pathogen or host as required (have self-receptors)
What is unique function of NK cells?
kill cells that have become altered due to stress/ infection
What are the 2 things activated NK cells perform?
- kill altered self-cell by releasing perforin/ granzymes/ inducing apoptosis
- produce cytokines that induce adaptive responses against altered self-cell
How do NK cells select what function? (induce apoptosis or produce cytokines for adaptive response)
induce apoptosis if activating receptors send stronger signals than their inhibitory receptors
What NK receptors recognize markers of infection/ stress on cells?
Activating receptors
What NK receptors recognize markers of normal cells (MHC ext)?
Inhibitory receptors
What are the innate lymphoid cells derived from?
common lymphoid progenitor cells
How many common lymphoid progenitor cells are there?
NK cells/ 6 other ILC populations
Where are NK cells found?
lymphoid tissue/ recirculate
Apart from NK cells where are the other ILCs found?
epithelium
Can ILCs be activated directly by pathogens?
no- lack PRRs
How many groups of ILCs are there?
3 = ILC1/ ILC2/ ILC3
What ILC is related to NK cells/ cytokines/ cell-mediated immunity?
ILC1
What ILC is related to cytokines/ parasite immunity/ wound healing?
ILC2
What ILC is related to cytokines./ epithelial integrity. lymphoid development/ bacteria/ fungi immunity?
ILC3
What innate immune systems are co-opted by adaptive immunity to contribute to antibody-mediated pathogen elimination?
Opsonization/ Complement activation
How are dendritic cells an innate/ adaptive bridge?
bring antigens from the infection site/ present to T cells in lymph nodes
- activates T cells- differentiate TH/TC
What is an example of pathogen avoiding detection by PRRs?
mutation in LPS (not recognized by TLR)
What is an example of pathogen blocking PRR signaling pathways- preventing activation/ response?
bacterial proteins with TIR domains that block MyD88/ TRIF
What is an example of a pathogen prevent killing?`
rupture phagosome/ escape into cytosol
