Innate immune system Flashcards
(118 cards)
1
Q
Through which surfaces do pathogens typically enter the body?
A
Mucosal and epithelial surfaces
2
Q
What must a pathogen do to cause infection?
A
It must breach anatomical barriers
3
Q
How do airborne microorganisms enter the body?
A
Through the lining of the respiratory tract
4
Q
What are the first barriers against infection provided by innate immunity?
A
-Skin
-Gut epithelium
-Respiratory epithelium
-Mucosal epithelium
5
Q
What substances provide innate immunity?
A
Saliva, hair, mucus, tears
6
Q
What protective substances do epithelial layers produce?
A
Acidic pH and antimicrobial peptides
7
Q
What are the cellular elements of innate immunity?
A
-Neutrophils and granulocytes
-Monocytes and macrophages
-Dendritic cells (immature and mature)
-Natural killer (NK) cells
8
Q
What do neutrophils and other granulocytes do?
A
Engulf and kill microorganisms
9
Q
What is phagocytosis?
A
Engulfment and internalization of pathogens
10
Q
Which cells mediate phagocytosis?
A
Macrophages, granulocytes, dendritic cells
11
Q
What are phagocytosis lead to?
A
Removal and killing of pathogens
12
Q
How do receptors mediate phagocytosis?
A
By binding to pathogens or their components
13
Q
What are opsonins?
A
Soluble proteins that enhance phagocytosis
14
Q
What initiates phagocytosis?
A
Interactions of receptors with ligands/pathogens
15
Q
What is a phagosome?
A
A membrane-enclosed vesicle containing a pathogen
16
Q
What happens when a phagosome fuses with lysosomes?
A
It forms a phagolysosome
17
Q
What occurs in the phagolysosome?
A
Acidification and release of antimicrobial substances
18
Q
What types of granules do neutrophils contain?
A
-Primary granules
-Secondary granules
19
Q
What triggers the process that kills phagocytosed pathogens ?
A
Phagocytosis and ligand binding signaling
20
Q
What products in phagolysosomes can kill microbes?
A
Low pH, hydrolytic enzymes, ROS
21
Q
What is the role of reactive oxygen species (ROS) in phagocytosis?
A
They damage microbial membranes and components
22
Q
What enzyme complex generates ROS in phagocytes?
A
NAPDH oxidase enzyme complex
23
Q
What is the respiratory burst in phagocytes?
A
Increased oxygen consumption during ROS production
24
Q
What are the functions of the phagolysosome in immunity?
A
-Pathogen killing
-Pathogen processing
-Antigen presentation
25
How do phagocytes clear apoptotic cells?
By recognizing DAMPs that signal "eat me"
26
What is the role of CD47 in phagocytosis?
It signals macrophages to inhibit phagocytosis
27
How do tumor cells evade phagocytosis?
By expressing elevated levels of CD47
28
What are the characteristics of neutrophils?
-Capable of phagocytosis
-Not tissue-resident
-Produce pus from dead cells
-Can form NETs to trap microorganisms
29
What roles do microglia play in the CNS?
-Establish neuronal connections
-Participate in debris clean-up
-Involved in brain development
-Contribute to memory and learning
30
What is multiple sclerosis characterized by?
Myelin breakdown and toxic debris in lesions
31
How do microglia contribute to CNS repair?
-Participate in debris clean-up
-Infiltrate with macrophages
32
What is the purpose of the experimental setup measuring phagocytosis?
To assess the impact of conditions on phagocytosis
33
What type of substrate is used in the phagocytosis experiment?
Dye substrate with pH-sensitive fluorophore
34
What does the dye substrate fluoresce under?
Low-pH conditions in phagolysosomeW
35
What is measures in macrophages during the experiment ?
Fluorescence before and after conditions
36
What does the term "complement system" refer to?
A group of soluble proteins in immunity
37
What is the primary function of the complement system?
To eliminate pathogens and dying cells
38
How many proteases are mostly involved in the complement system?
More than 30
39
What is a protease?
An enzyme that breaks down proteins
40
How are complement proteins mostly named?
By "C" followed by a number
41
Where are complement proteins primarily produced?
In the liver
42
What are the key mechanisms of action of the complement system?
Increasing permeability, destroying membranes, opsonization
43
What is opsonization and its significance?
-Coating of pathogens by antibodies/ complement
-Enhances ingestion by phagocytes
44
What is phagocytosis?
-Internalization of particles by cells
-Engulfment forms an intracellular vesicle (phagosome)
45
How are complement components initially found?
As inactive pro-proteases
46
How many ways can complement be activated and what are they called?
They are 3 pathways:
-Classical
-Alternative
-Lectin
47
What happens during the activation of complement proteins?
Proteolytic cleavage generates two fragments
48
What identifies the small fragment after complement cleavage?
Letter "a" after the name
49
What identifies the large fragment after complement cleavage?
Letter "b" after the name
50
what is the function of C3 convertase?
Cleaves C3 into C3a and C3b
51
What is the role of the C3b in the alternative pathway?
Amplifies C3b formation on pathogens
52
what stabilizes the alternative pathway C3 convertase?
Factor properdin (factor P)
53
What are the main outcomes of complement activation?
-Inflammation
-Increased phagocytosis
-Pathogen lysis (MAC formation)
54
How do C3a and C5a contribute to inflammation?
They recruit phagocytes and promote inflammation
55
What receptors connect complement-tagged pathogens to effector cells?
C3aR and C5aR on granulocytes
56
How does opsonization enhance phagocytosis?
Phagocytes have receptors for C3b
57
What is the membrane-attack complex (MAC)?
A structure that lyses pathogen cells
58
What is the role of complement-regulatory proteins
Prevent inapropriate complement activation
59
What is the main function of the C3 convertase?
Cleaves C3 into C3a and C3b
60
What happens if C3a and C5a are present in large amounts?
They can cause anaphylactic shock
61
What is the significance of the complement system in immunity?
It enhances both innate and adaptive immune responses
62
What are the two types of C3 convertases?
C4b2a and C3bBb
63
What does C3b do in the immune response?
Involved in opsonization and C5 convertase
64
What is the role of C3a in the immune system ?
Involved in the inflammation
65
What is the function of C5a?
Involved in inflammation
66
What does C5b do in the immune response?
Involved in MAC formation
67
What are Pathogen-Associated Molecular Patterns (PAMPs)?
-Specific molecular patterns of pathogens
-support pathogen lifestyle
-Recognized by Pattern Recognition Receptors (PRRs)
68
Where are PRRs located?
On host cells and in the host cells
69
What do DAMPs stand for?
Damage-Associated Molecular Patterns
70
Which white blood cells have PRRs?
All types of myeloid white blood cells
71
What type of cells express PRRs?
Myeloid and some lymphoid cells
72
What are Toll-like receptors (TLRs)?
A group of PRRs
73
What is the significance of receptor location in TLRs?
-Determines corresponding PAMP binding
-Intracellular vs extracellular receptors
74
What happens when TLRs bind PAMPs?
Activates signaling pathways
75
What are some transcription factors activated by TLR signaling ?
NF-κB, IRF, and AP-1
76
What is phosphorylation in signaling caascades?
Addition of a phosphoryl group to a molecule
77
What is the central dogma of molecular biology?
DNA → mRNA → protein
Each gene has a promoter
Transcription factors bind to promoters
78
What do C-Type Lectin Receptors (CLRs) bind to?
Carbohydrates on pathogens and allergens
79
What do RIG-I-like-Receptors (RLRs) recognize?
Viral double-stranded RNAs
80
What is the function of NOD-like Receptors (NLRs)?
Recognize peptidoglycan from bacterial cell walls
81
What does caspase-1 do in immune response?
Cleaves IL-1β/IL-18 into active forms
82
What are the general features of signal transduction?
Ligand-induced receptor dimerization
Activation of kinases and adaptors
Changes in gene expression
83
What is ubiquitination?
Attachment of ubiquitin to a target protein
84
What is the role of PRRs in the immune response?
Recognize PAMPs and trigger signaling cascades
85
What are the effects of PRR signaling ?
Cytokine production, chemokine production, migration
86
What is produced after PRR signaling?
-Cytokines
-Chemokines
-Costimulatory molecules
-Upregulation of specific adhesion molecules
87
What is the role of Type I IFN produced by PRR signaling?
-It has potent antiviral effects
-it triggers signaling and leads to more transcription which make genes that are able to inhibit viral replication
88
What are CC and CXC chemokines?
Types of chemokines with different cysteine locations
89
What do costimulatory molecules B7.1 and B7.2 provide to T cells?
They provide SIGNAL 2 in lymphoid tissue
90
What are chemokines receptors an example of?
Chemokines receptors are an example of G-protein-coupled receptors
91
What are cytokines primarily classified as?
Small heterogenous glycoproteins
92
What is the typical size of cytokines?
Approximately 25kD
93
Are cytokines mostly soluble or membrane-bound?
Mostly soluble
94
How are cytokine production regulated?
Through post-transcription/translation modifications
95
What is the primary function of cytokines?
Provide cellular communication
96
What are the three mechanisms through which cytokines affect cell behavior?
Autocrine mechanism: affects the producing cell
Paracrine mechanism: affects adjacent cells
Endocrine mechanism: affects distant cells
97
What triggers cytokines production ?
Inducing stimulus
98
What are some biological functions of cytokines?
Activation, proliferation, differentiation, survival
99
What can cytokines change on target cell membranes?
Expression of adhesion molecules
100
How do cytokines affect enzyme activity?
They can increase or decrease activity?
101
What is cascade induction in cytokine action?
One cytokine induces another to produce more
102
What are the five major groups of cytokines?
1. Interleukins (IL)
2. Interferons (IFN)
3. Tumor necrosis factors (TNF)
4. Hematopoietins or growth factors
5. Chemokines
103
What is pleiotropy in cytokine function ?
One cytokine produces multiple effects
104
What does redundancy mean in cytokine action?
More than one cytokine induce the same effect
105
What is synergy in cytokine interactions?
Two or more cytokines work together
106
What does antagonism mean in cytokine function?
One cytokine inactivates another's effect
107
Describe the cytokine network?
Same cytokine produced by multiple cells
Each cell type can produce multiple cytokines
Complex interactions occur
Specific cytokines produced at different times and locations
108
How do cytokines imprint adaptive responses?
They influence T cell differentiation
109
What characterized cell-mediated immunity?
Directed to viral infections and intracellular pathogens
Involves T helper cell activation
Involves cytotoxic T lymphocyte (CTL) activation
110
What characterizes humoral immunity?
Directed to extracellular bacteria/pathogens
Involves B cell activation
Involves antibody production
111
What role does TNF-α play in inflammation?
It is a proinflammation cytokine
112
What cells secrete TNF-α ?
Macrophages
113
What are the effects of local TNF-α ?
Causes local inflammation
114
What are the effects of systemic TNF-α?
Causes systemic effects
115
What is the acute phase response?
Change in blood proteins during infection
Induced by proinflammatory cytokines (IL-1, TNF-α, IL-6)
Involves increased synthesis of antimicrobial proteins from the liver
116
What is the role of C-reactive protein?
Opsonizes bacteria and triggers complement cascade
117
What do inflammatory cytokines like IL-1β, IL-6, and TNF-α do?
They mobilize cells and induce fever
118
How does fever occur in response to inflammatory cytokines?
They signal to hypothalamus to increase temperature
