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Immune System Flashcards

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1
Q

What is an immune system?

A

A network that protects us from disease.

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2
Q

Immune system division

A
  1. Innate immune system
    . Humoral (Macromolecules in extracellular fluid)
    . Cell- mediated (Immune cells)
  2. Adaptive (Acquired) immune system
    . Humoral
    . Cell-mediated
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3
Q

Antibodies are also called

A

Immunoglobulin (Ig)

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4
Q

How does the immune system recognize a foreign object?

A

By identifying PAMPS (Pathogen associated molecular patterns), which can be made from various molecules (lipids, carbs, and nucleic acids)

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5
Q

Pathogen types

A
  1. Extracellular pathogen
    . Can be anything except viruses
  2. Intracellular pathogen
    . Can be anything
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6
Q

Innate immune system division

A

First Line Defense
. Physical/ chemical barriers
Second Line Defense
. Leukocytes
. Physiological response (Fever, and inflammation)
. Chemicals

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7
Q

Leukocytes of the immune system

A
  1. Neutrophils
  2. Monocytes
    . Macrophage
  3. Dendritic cell
  4. NK cells
  5. Basophil
  6. Eosinophil
  7. Mast cell
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8
Q

Physiological responses

A
  1. Inflammation
    . Increased fluid and leukocyte flow
    . Cytokines, prostaglandin and histamine stimulate inflammation
  2. Fever
    . Endogenous pyrogenic interleukins (which are a type of cytokine) can induce fever.
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9
Q

Chemicals

A
  1. Interferons ( a type of cytokines that alert the body of infection or cancer)
    . Tell other nearby cells to increase their antiviral defense
    . Call leukocytes to kill
  2. Complement proteins
    . Inactive proteins that activate during infection
    . Kill pathogens directly
    . Opsonisation (tag pathogens for phagocytosis)
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10
Q

Monocyte is precursor for _______

A

Macrophage and dendritic cells

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11
Q

List all leukocytes of the innate immune system

A
  1. Monocytes
  2. Dendritic cells
  3. Macrophages
  4. Granulocytes
    . Neutrophil
    . Basophil
    . Eosinophil
    . Mast cell
  5. Natural killer
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12
Q

List all granulocytes

A

. Neutrophil
. Basophil
. Eosinophil
. Mast cell

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13
Q

______ is the most abundant leukocytes in human body

A

Neutrophil

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14
Q

______ is the first responder to infection

A

Neutrophil

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15
Q

Neutrophil’s functions

A

. Recruit other leukocytes
. Phagocytosis
. Kill or inhibit bacteria/ fungi

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16
Q

__________ (leukocytes) damage tissue

A

Eosinophil

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17
Q

Eosinophil function

A

. Granule kill bacteria, parasite and worm
. Phagocytosis
. Cause tissue damage

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18
Q

_______ ( leukocytes in the innate immune system) is responsible for allergic reaction

A

Basophil and mast cells

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19
Q

Basophil function

A

. Granules produce histamine
. Kill parasite

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20
Q

Where are neutrophil, basophil, and eosinophil found in?

A

Blood vessels but they can migrate to infected tissue

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21
Q

Mast cell function

A

. Produce histamine and heparin
. Causes inflammation

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22
Q

Where is mast cell found?

A

In connective tissue, blood vessels, and mucous membranes

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23
Q

List other leukocytes of the innate immune system excluding the granulocytes

A
  1. Monocytes
  2. Dendritic cells
  3. Macrophages
  4. Natural killer
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24
Q

Monocytes’ function

A

In response to inflammation, turn into macrophages or dendritic cells

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25
Where is monocytes found in?
Stored in spleen Move through vessels Activated in inflamed tissue
26
Macrophage and dendritic cell’s function
. Phagocytosis . Antigen presentation to the adaptive immune system
27
Where are dendritic cells found ?
Epithelial tissue, skin, lungs, GI tract, and stomach Once they have antigen to present, they go to lymph nodes
28
NK is a type of _______
Lymphocytes
29
NK cell’s function
Induce apoptosis to compromised cells by scanning the MHC- 1. If it is defective or non existent, it produces granzymes and perforins.
30
Where is natural killer found?
Vessels but migrate to infected site.
31
How do NK cells identify which cell to kill?
1. MHC-1 (Major histocompatibility class 1 molecule) is a complex that presents its own peptide to NK. 2. If the MHC-1 is deformed or non-existent, apoptosis is induced.
32
How do macrophages and dendritic cells present pathogenic antigens?
Via MHC-2
33
On which cells is MHC2 found?
Macrophage, dendritic cells, B lymphocytes
34
Macrophages call T-helper cells via ________
Interleukins (A type of cytokines) Especially IL-1
35
Interferons function
Interferons are a class of cytokines produced by compromised cell to alert nearby cells to increase antiviral defenses, and call leukocytes to site for killing pathogens, and compromised cell. They are under the second line of defense (chemicals) in the innate immune system. They are in
36
What do complement proteins do?
They mark pathogens for phagocytosis (opsonisation), or they bind to the pathogen and kill by forming a complex
37
What do interleukins do?
They induce fever, and they are produced by certain leukocytes (macrophage) to call lymphocytes to the infection site.
38
What is an antigen?
It is a foreign macromolecule that generates an immune response
39
Humoral immunity of the adaptive immune system primarily means …
Antibodies produced by B-lymphocytes
40
Humoral immunity of the adaptive immune system (process)
1. Macrophage or dendritic cell present foreign antigen on MHC2. 2. They also release interleukins to attract T-helper cells on site. 3. B- lymphocytes bind to antigen on macrophage. 4. Helper-T cells bind to macrophages, and become activated. 5. Activated T-helper cells activate B-lymphocytes. 6. B-lymphocytes divide by mitosis to form plasma cells or memory cells. 7. Plasma cells secrete antibodies, and bind to the antigen.
41
Cell mediated adaptive immune response primarily means …
T- lymphocytes . CD4 (T helper cells) . CD8 (Cytotoxic T cells) . T- suppressor cells . T-helper cells
42
Helper T cells’ function
. Bind to MHC2 to become activated . Activate Cytotoxic T cells, and B-lymphocytes. . Enhance macrophage activity . Help T-lymphocytes differentiate into cytotoxic T cells
43
Cytotoxic T cells’ function
. Contain T-cell receptor which recognizes specific antigens . Bind to MHC-1 . Kills pathogens, and compromised cells by releasing perforins, and granzymes.
44
T-suppressor cells’ function
. Prevent the immune system from attacking the body . Helps the immune system know what is self and non- self
45
List all lymphocytes
1. T-helper cells 2. Cytotoxic T-cells 3. B-lymphocytes 4. T-suppressor cells 5. Natural killer cells
46
List Antigen presenting cells
1. B-lymphocytes 2. Macrophage 3. Dendritic cells
47
T-helper cell has _____ on their membrane which binds to ______
TCR (T- cell receptor) on T-helper cells bind binds to antigen. CD4 receptor binds to MHC-2.
48
How do cytotoxic-T cells kill cells?
The CD-8 receptor on killer T cells binds to MHC-1, and it releases perforins, and induce apoptosis.
49
Antibody’s structure
. Y-shaped protein . Two heavy chains and two light chains blinded by disulfide bridges . Have constant region and variable region . Have antigen binding site
50
The area of the antigen that binds the immunoglobulin
Epitope
51
Epitope
The area of the antigen that binds the immunoglobulin
52
How do antibodies kill/ inhibit pathogen?
1. Opsonisation 2. Agglutination 3. Neutralization 4. Complement activation
53
For the B-lymphocyte to be activated, the following conditions must be met.
1. An antigen must bind to the B-cell receptor (membrane bound antibody). 2. T-helper cells bind must bind to the antigen carrying MHC-2 on B-cell with its T-cell receptor.
54
Does naive B-cells produce antibodies?
Yes, they have membrane bound antibody known as the B-cell receptor.
55
The membrane bound immunoglobulin on B-lymphocyte is also known as the _____
B cell receptor
56
B cell receptor is also known as ____
Membrane bound immunoglobulin (antibody) on the surface of B lymphocytes
57
B cells need two signals to be activated:
(1) Antigen binding to BCR, (2) Help from an activated CD4+ T helper cell via MHC II, CD40L, and cytokines.
58
CD4 receptor on T-helper cell binds to the ______ T cell receptor binds to the ________
CD4 receptor on T-helper cell binds to the MHC2 T cell receptor binds to the Antigen on the MHC2
59
CD8 receptor on Cytotoxic T cell binds to the ______ T cell receptor binds to the ________
CD8 receptor on Cytotoxic T cell binds to the MHC1 T cell receptor binds to the antigen
60
What is the main function of neutrophils?
Fast responders that perform phagocytosis of bacteria and fungi.
61
What is the most common type of leukocyte?
Neutrophils.
62
Which leukocyte type recruits other leukocytes to infection sites?
Neutrophils.
63
Are neutrophils more involved in bacterial or parasitic infections?
Bacterial (and fungal) infections.
64
What is the primary role of eosinophils?
Defense against parasites and worms.
65
Which granulocyte contributes to tissue damage in allergic reactions?
Eosinophils.
66
Can eosinophils perform phagocytosis?
Yes, but mainly for bacteria (minor role compared to neutrophils).
67
What do basophil granules release?
Histamine.
68
What immune response are basophils mainly involved in?
Allergy (allergic reactions).
69
Do basophils have any role in killing parasites?
Yes, but their main function is allergy.
70
Where are mast cells mainly found?
In connective tissue and mucous membranes (not blood).
71
What two substances do mast cell granules contain?
Histamine and heparin.
72
What is the main immune role of mast cells?
Triggering local inflammation and allergic responses.
73
Which two granulocytes are most responsible for inducing allergies?
Basophils and mast cells.
74
Which granulocyte is the only one mainly resident in tissue instead of blood?
Mast.
75
What do monocytes become when activated in tissue?
Macrophages or dendritic cells.
76
Where are monocytes stored and how do they travel?
Stored in the spleen; move through the blood.
77
When do monocytes get activated?
When they enter tissues, especially during inflammation.
78
What is the main function of macrophages?
Phagocytosis of pathogens and dead cells.
79
Where do macrophages originate from?
From monocytes that have entered tissues.
80
Besides phagocytosis, what is another role of macrophages?
Present antigen residues to the adaptive immune system.
81
Where are macrophages mostly found?
In tissues (after migrating from blood).
82
What is the main function of dendritic cells?
Phagocytosis and antigen presentation.
83
Where are dendritic cells mainly found?
Epithelial tissue, skin, lungs, GI tract, stomach.
84
What do dendritic cells do after capturing an antigen?
Move to lymph nodes to present the antigen to T cells.
85
What is the primary function of NK cells?
Induce apoptosis in compromised (infected or cancerous) cells.
86
What type of leukocyte are NK cells?
Lymphocytes (innate immune system).
87
Where do NK cells operate?
In the blood and tissues.
88
Which cell is a lymphocyte but is part of the innate immune system?
NK cell.
89
Which cells link the innate and adaptive immune systems through antigen presentation?
Macrophages and dendritic cells.
90
What is the main reason dendritic cells are found in certain areas of the body?
They are positioned at barrier sites to detect invading pathogens early. ## Footnote Dendritic cells play a crucial role in the immune response by acting as sentinels at the body's interfaces with the external environment.
91
Where are dendritic cells most commonly found in the body?
In the skin and mucosal surfaces. ## Footnote These areas are critical for immune surveillance and pathogen detection.
92
Which organ is the largest barrier and a major location for dendritic cells?
The skin. ## Footnote The skin serves as the first line of defense against pathogens.
93
Which mucosal surfaces are rich in dendritic cells?
The respiratory tract (lungs), gastrointestinal tract (stomach, intestines), and genitourinary tract. ## Footnote These surfaces are exposed to many potential pathogens.
94
Why are dendritic cells concentrated at barrier tissues like the gut and lungs?
These are common entry points for pathogens, so dendritic cells can capture invaders quickly. ## Footnote This strategic positioning enhances the immune response.
95
What do dendritic cells do once they capture an antigen at a barrier site?
They migrate to lymph nodes to present the antigen to T cells. ## Footnote This process is vital for initiating a specific immune response.
96
What is a simple way to remember where dendritic cells are located?
Think 'border patrol'—they guard the skin and mucosal entry points. ## Footnote This analogy helps conceptualize their protective role.
97
Are dendritic cells found inside internal organs like the liver or heart under normal conditions?
No, they are mainly at body surfaces exposed to the external environment. ## Footnote Their presence is limited to areas where they can encounter pathogens.
98
Which barrier sites would NOT be a major location for dendritic cells?
Deep internal organs that are not in direct contact with the outside world. ## Footnote Dendritic cells are primarily located at interfaces with the environment.
99
What is the main function of dendritic cells at these barrier sites?
To detect and process antigens from pathogens as soon as they enter the body. ## Footnote This function is essential for the activation of the adaptive immune system.
100
What are monocytes precursors for?
Macrophages and dendritic cells.
101
Where are monocytes stored and how do they travel?
Stored in the spleen, move through blood vessels.
102
What triggers monocytes to leave the blood and enter tissues?
Inflammation or infection.
103
What do monocytes become after migrating into inflamed tissue?
Macrophages or dendritic cells.
104
What do macrophages and dendritic cells have in common?
Both phagocytose pathogens and present antigens on MHC class II.
105
What is the main function of macrophages after antigen presentation?
Remain in tissue and help activate local immune responses.
106
What unique step do dendritic cells perform after antigen uptake?
Migrate to lymph nodes to present antigens to T-cells.
107
Which cell is the most effective at activating naïve T-cells?
Dendritic cells.
108
What is the main function of NK cells in the immune system?
Destroy compromised cells by inducing apoptosis.
109
How do NK cells recognize which cells to kill?
They detect cells with reduced or absent MHC class I molecules.
110
What molecules do NK cells release to kill target cells?
Perforins and granzymes.
111
Where do NK cells circulate and act?
They move in the blood and can migrate into tissues.
112
Q: Which antigen-presenting cell is best at activating naive CD4+ and CD8+ T-cells?
A: Dendritic cells.
113
1. Q: Which cells are considered professional antigen-presenting cells (APCs)?
A: Dendritic cells, macrophages, and B lymphocytes.
114
2. Q: Are T lymphocytes (T-cells) professional APCs?
A: No.
115
Which cells express MHC class II?
Dendritic cells, macrophages, and B lymphocytes.
116
Do T lymphocytes express MHC class II under normal conditions?
No, they do not.
117
What is the B-cell receptor (BCR)?
A membrane-bound immunoglobulin that binds specific antigens. ## Footnote BCRs are essential for the activation of B cells in the immune response.
118
What happens after a B cell binds its specific antigen?
The antigen is internalized, processed, and presented on MHC class II. ## Footnote This process is crucial for the activation of helper T cells.
119
Which molecule presents processed antigen on the B cell surface?
MHC class II. ## Footnote MHC class II molecules are primarily found on professional antigen-presenting cells.
120
Which T cell interacts with the B cell’s MHC II-antigen complex?
CD4+ helper T cell. ## Footnote CD4+ T cells play a pivotal role in orchestrating the immune response.
121
What do helper T cells use to recognize the antigen-MHC II complex?
Their T cell receptor (TCR) and CD4 molecule. ## Footnote This interaction is essential for T cell activation and subsequent immune responses.
122
What is the result of helper T cell binding to antigen-presenting B cell?
Helper T cell gets activated and provides co-stimulatory signals. ## Footnote Co-stimulatory signals are necessary for full B cell activation.
123
What do helper T cells secrete to fully activate B cells?
Cytokines (e.g., IL-4, IL-5). ## Footnote These cytokines promote B cell proliferation and differentiation.
124
What do activated B cells differentiate into?
Plasma cells (produce antibodies) and memory B cells. ## Footnote Plasma cells are responsible for the production of antibodies, while memory B cells provide long-term immunity.
125
How do natural killer (NK) cells recognize which cells to kill?
They look for cells with missing or defective MHC class I molecules. ## Footnote MHC class I molecules are crucial for immune recognition.
126
What do NK cells do if a cell has no or abnormal MHC class I?
Induce apoptosis in that cell. ## Footnote Apoptosis is a form of programmed cell death.
127
Why do some virus-infected or cancer cells lose MHC class I?
To evade detection by cytotoxic T cells. ## Footnote This is a common mechanism of immune evasion by tumors and viruses.
128
How do cytotoxic T (CD8+) cells recognize target cells?
By detecting foreign antigens presented on normal MHC class I molecules. ## Footnote CD8+ T cells are essential for targeting infected or malignant cells.
129
What do cytotoxic T cells do when they find a cell with a foreign antigen on MHC I?
Induce apoptosis in that cell. ## Footnote This mechanism is crucial for eliminating infected or cancerous cells.
130
Do cytotoxic T cells respond to the absence of MHC class I?
No, they require MHC class I to present the antigen. ## Footnote This highlights the difference between T cell and NK cell activation.
131
Which cell type responds to the absence of MHC class I?
NK cells. ## Footnote This characteristic allows NK cells to target cells that have downregulated MHC expression.
132
Which cell type responds to foreign antigens on MHC class I?
Cytotoxic T (CD8+) cells. ## Footnote This specificity is fundamental for adaptive immunity.
133
How do natural killer (NK) cells recognize which cells to kill?
They look for cells with missing or defective MHC class I molecules. ## Footnote MHC class I molecules are crucial for immune recognition.
134
What do NK cells do if a cell has no or abnormal MHC class I?
Induce apoptosis in that cell. ## Footnote Apoptosis is a form of programmed cell death.
135
Why do some virus-infected or cancer cells lose MHC class I?
To evade detection by cytotoxic T cells. ## Footnote This is a common mechanism of immune evasion by tumors and viruses.
136
How do cytotoxic T (CD8+) cells recognize target cells?
By detecting foreign antigens presented on normal MHC class I molecules. ## Footnote CD8+ T cells are essential for targeting infected or malignant cells.
137
What do cytotoxic T cells do when they find a cell with a foreign antigen on MHC I?
Induce apoptosis in that cell. ## Footnote This mechanism is crucial for eliminating infected or cancerous cells.
138
Do cytotoxic T cells respond to the absence of MHC class I?
No, they require MHC class I to present the antigen. ## Footnote This highlights the difference between T cell and NK cell activation.
139
Which cell type responds to the absence of MHC class I?
NK cells. ## Footnote This characteristic allows NK cells to target cells that have downregulated MHC expression.
140
Which cell type responds to foreign antigens on MHC class I?
Cytotoxic T (CD8+) cells. ## Footnote This specificity is fundamental for adaptive immunity.
141
Does each cytotoxic T cell recognize a different foreign antigen?
Yes, each has a unique TCR specific for one antigen-MHC I complex.
142
What is the similarity between cytotoxic T cells and B lymphocytes in terms of antigen recognition?
Both have unique receptors (TCR for T cells, BCR for B cells) specific to different antigens.
143
Why can the immune system recognize many different foreign antigens?
Because there are millions of different cytotoxic T cells and B cells, each with a unique receptor.
144
Q: What are the key steps of T-dependent B cell activation and antibody production?
A: 1. Pathogen enters body. 2. Dendritic cell phagocytoses pathogen, presents antigen on MHC II to activate helper T cell in lymph node. 3. B cell binds free antigen with its receptor, internalizes and presents it on MHC II. 4. Activated helper T cell binds to B cell’s MHC II-antigen complex and provides cytokines. 5. B cell activates, proliferates into plasma and memory cells. 6. Plasma cells secrete antibodies.
145
Q: How does a cytotoxic T cell (CD8+) kill a compromised cell?
A: The T cell receptor (TCR) binds to a specific foreign antigen on MHC class I. If the antigen is foreign, the cytotoxic T cell releases perforins and granzymes, causing apoptosis of the target cell.
146
What do helper T cells (CD4+) secrete to activate cytotoxic T cells (CD8+)?
Cytokines, especially interleukin-2 (IL-2).
147
Do helper T cells help activate both B cells and cytotoxic T cells?
Yes, by producing cytokines and providing co-stimulatory signals.
148
What is another name for regulatory T cells?
T suppressor cells.
149
What is the main function of regulatory (suppressor) T cells?
To suppress the immune system and prevent it from attacking self (autoimmunity).
150
How do regulatory T cells help prevent autoimmunity?
By helping the immune system distinguish self from non-self and suppressing immune attacks on the body’s own cells.
151
Are plasma cells considered lymphocytes?
Yes, they are differentiated B lymphocytes. ## Footnote Plasma cells are responsible for producing antibodies.
152
Are memory cells considered lymphocytes?
Yes, memory cells can be either B or T lymphocytes. ## Footnote Memory cells play a crucial role in the immune response by 'remembering' past infections.
153
Which cell types are included in the lymphocyte group?
B cells, T cells, NK cells, plasma cells, and memory cells. ## Footnote These cells are essential components of the adaptive immune system.
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