Opsonization and phagocytosis Flashcards
___ is the process of attaching opsonins, such as IgG or complement fragments, to microbial ___ to target the microbes for ___.
Opsonization; surfaces; phagocytosis
what cells have receptors that can recognize macromolecules attached to the surface of a microbe?
neutrophils and macrophages
What are the two primary opsonins?
IgG and complement factor C3
T/F. Most microorganisms will be phagocytosed without opsonins.
False, most microorganisms will NOT be phagocytosed without opsonins.
___ extend to cover particle (but only the part that is opsonized).
Pseudopods
Changes the organism’s surface from ___ (relative to the PMN) to more ___ increases ingestion.
hydrophilic; hydrophobic
IgG antibodies bind to microbes and are then recognized by ___ receptors on phagocytes.
Fc
___ receptor signals activate phagocyte and leads to engulfment of the particles. The particles are internalized into vesicles known as ___, which fuse with ___, and the phagocytosed particles are destroyed in these phagolysosomes.
Fc; phagosomes; lysosomes
T/F. IgG, not complement fragments, mediate opsonization.
False. IgG and complement fragments mediate opsonization.
Binding of ___ to microbe by recognition of the ___ receptor causes ___ of the microbe.
C3b; C3b; phagocytosis
Cell bound ___ is an opsonin that promotes phagocytosis.
C3b
Complement activation leads to ___ activation and inflammation and tissue injury.
neutrophil
What are the receptors for opsonins?
FCgamma on phagocytes
CR and leukocyte integrin Mac-1
The Fc receptors are grouped based on what?
their affinity for heavy chains of different IgGs
What are the two FcRs have a high affinity for immunoglobulin?
FCgammaRI and FCepisilonRI
What region of the IgG receptor reacts with organism?
Fab-region
What region of the IgG receptor is FcgammaR?
Fc domain on PMN
T/F. The loss of CD16 “bright” peak is a signal for macrophages to phagocytose the neutrophils- they signal that they are apoptotic.
True
What Fcgamma R subtype is the most important for phagocytosis of IgG coated particles and microorganisms?
RII
Activation of ___ cascade causes proteolytic cleavage of complement factors creating potential ligands for complement receptors on neutrophil surfaces.
complement
What type of complement related proteins are C3a and C5a?
chemotactic factors
What type of complement related proteins are C3b and C3bi?
the main complement derived opsonins
How many complement receptors are there?
4
what is the major phagocytic cell in the innate immune response?
neutrophils
What phagocytic cell is continually circulating, binding and releasing from the vascular endothelia and contains granules in the cytoplasm responsible for killing microbes?
neutrophils
Matching: What does each neutrophil receptor recognize on bacteria?
- LPS receptor
- CR3,4
- Scavenger receptor
- Mannose receptor
- Glycan receptor:
A. Complement (C’) receptors (C3b) B. CD14 C. toll-like receptor-4 D. Polysaccharides E. sialic acid-bearing protein F. Binds mannose on bacteria, activates C’
- B,C
- A
- E
- F
- D
What cell that circulates in the blood and eventually move into the tissues to become macrophages functions to phagocytosize and produce cytokines?
monocytes
Match:
- Lung
- Liver
- Bone
- Connective tissue
- Kidney
- Brain
A. Kupfer cells B. Mesangial C. Osteoclasts D. Histocytes E. Microglial cells F. alveolar macrophages
- F
- A
- C
- D
- B
- E
What receptors are found on macrophages?
LPS receptor-CD14 Toll-like receptors Fc receptors Mannose receptor Complement receptors IFNg receptor Chemokine receptors
T/F. Stress and injury are factors that increase PMNs but infection and increased cytokines decrease PMNs.
False. All (stress, injury, infection and increased cytokines) increase PMNs
What are the two mechanisms for destruction and killing?
oxidative
non-oxidative (enzymes and cytoplasmic granules and pH changes)
Once the microbes are inside a phagolysosome, how are they killed?
by ROS and NO
What are the five phagocytic cells?
neutrophils (polymorphonuclear leukocytes - PMNs) macrophages/monocytes eosinophils basophils dendritic cells
T/F. Macrophages ingest and degrade gram-negative bacteria and is activated by LPS to secrete cytokines.
True.
What two cytokines cause local AND systemic effects?
IL-1, TNFalpha and IL-6
What tactics are used by pathogens to avoid killing by phagocytes?
- kill or be killed
- inhibit opsonization or inactivate phagocytosis
- survive intracellular killing
