Chapter 8: The Immune System Flashcards
1
Q
Structure of the Immune System
A
START
2
Q
The immune system can be divided into
A
- innate
- adaptive immunity
3
Q
Innate immunity is composed of
A
defenses that are always active, but that cannot target a specific invader and cannot maintain immunologic memory; also called nonspecific immunity.
4
Q
____ is composed of defenses that are always active, but that cannot target a specific invader and cannot maintain immunologic memory; also called _____.
A
**Innate immunity
nonspecific immunity**
5
Q
Adaptive immunity is composed of
A
defenses that take time to activate, but that target a specific invader and can maintain immunologic memory; also called specific immunity.
6
Q
____ is composed of defenses that take time to activate, but that target a specific invader and can maintain immunologic memory; also called ____.
A
Adaptive immunity
specific immunity
7
Q
The immune system is dispersed in the body.
A
- Immune cells come from the bone marrow.
- The spleen and lymph nodes are sites where immune responses can be mounted, and in which B-cells are activated.
- The t_hymus_ is the site of T-cell maturation.
- Gut-associated lymphoid tissue (GALT) includes the tonsils and adenoids.
8
Q
____, or white blood cells, are involved in ____.
A
Leukocytes
immune defenses
9
Q
Leukocytes aka what?
A
white blood cells
10
Q
The Innate Immune System
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START
11
Q
Many of the nonspecific defenses are
A
noncellular
- The skin acts as a physical barrier and secretes antimicrobial compounds, like defensins.
- Mucus on mucous membranes traps pathogens; in the respiratory system, the mucus is propelled upward by cilia and can be swallowed or expelled.
- Tears and saliva contain lysozyme, an antibacterial compound.
- The stomach produces acid, killing most pathogens. Colonization of the gut helps prevent overgrowth by pathogenic bacteria through competition.
- The complement system can punch holes in the cell walls of bacteria, making them osmotically unstable.
- Interferons are given off by virally infected cells and help prevent viral replication and dispersion to nearby cells.
12
Q
The skin acts as a
A
physical barrier and secretes antimicrobial compounds, like defensins.
13
Q
Mucus on mucous membranes traps
A
pathogens; in the respiratory system, the mucus is propelled upward by cilia and can be swallowed or expelled.
14
Q
Tears and saliva contain
A
lysozyme, an antibacterial compound.
15
Q
The stomach produces acid doing what?
A
The stomach produces acid, killing most pathogens. Colonization of the gut helps prevent overgrowth by pathogenic bacteria through competition.
16
Q
The complement system can
A
The complement system can punch holes in the cell walls of bacteria, making them osmotically unstable.
17
Q
Interferons are given off by
A
virally infected cells and help prevent viral replication and dispersion to nearby cells.
18
Q
Many of the nonspecific defenses are also
A
cellular
- Macrophages ingest pathogens and present them on major histocompati-bility complex (MHC) molecules. They also secrete cytokines.
- MHC class I (MHC-I) is present in all nucleated cells and displays endogenous antigen (proteins from within the cell) to cytotoxic T-cells (CD8+ cells).
- MHC class II (MHC-II) is present in professional antigen-presenting cells (macrophages, dendritic cells, some B-cells, and certain activated epithelial cells) and displays exogenous antigen (proteins from outside the cell) to helper T-cells (CD4+ cells).
19
Q
Macrophages do what ?
A
Macrophages ingest pathogens and present them on major histocompati-bility complex (MHC) molecules. They also secrete cytokines.
20
Q
MHC class I (MHC-I) is present in all
A
nucleated cells and displays endogenous antigen (proteins from within the cell) to cytotoxic T-cells (CD8+ cells).
21
Q
MHC class II (MHC-II) is present in
A
professional antigen-presenting cells (macrophages, dendritic cells, some B-cells, and certain activated epithelial cells) and displays exogenous antigen (proteins from outside the cell) to helper T-cells (CD4+ cells).
22
Q
Dendritic cells are
A
antigen-presenting cells in the skin.
23
Q
Natural killer cells attack
A
Natural killer cells attack cells not presenting MHC molecules, including virally infected cells and cancer cells.
24
Q
Granulocytes include
A
Granulocytes include neutrophils, eosinophils, and basophils.
esosino
baso
neutro
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**_Neutro_**phils ingest
bacteria, particularly opsonized bacteria (those marked with antibodies). They can follow bacteria using chemotaxis.
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**_Eosino_**phils are used in
_allergic reactions_ and _invasive parasitic infections_.
They release _histamine_, causing an inflammatory response.
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**_Baso_**phils are used in
_allergic reactions_.
Mast cells are related cells found in the skin.
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The Adaptive Immune System
START
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Humoral immunity is
centered on antibody production by _plasma cells_, which are activated _B-cells_.
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Antibodies target a
antigen.
* Antibodies target a particular antigen. They contain two heavy chains and two light chains. They have a constant region and a variable region; the tip of the variable region is the antigen-binding region.
* When activated, the antigen-binding region undergoes hypermutation to improve the specificity of the antibody produced. Cells may be given signals to switch isotypes of antibody (IgM, IgD, IgG, IgE, IgA).
* Circulating antibodies can opsonize pathogens (mark them for destruction), cause agglutination (clumping) into insoluble complexes that are ingested by phagocytes, or neutralize pathogens.
* Cell-surface antibodies can activate immune cells or mediate allergic reactions.
* **Memory B-cells** lie in wait for a second exposure to a pathogen and can then mount a more rapid and vigorous immune response (secondary response).
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_Antibodies_ target a particular
**antigen.**
**Antigen:** a toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
They contain _two heavy chains_ and _two light chains_.
They have a **constant region** and a **variable region**; the tip of the **variable region** is the antigen-binding region.
32
When activated, the **antigen-binding region** undergoes
_hypermutation_ to _improve the specificity of the antibody produced_. Cells may be given signals to switch isotypes of antibody (IgM, IgD, IgG, IgE, IgA).
A, E, M, D, G
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**Circulating antibodies** can
opsonize pathogens (mark them for destruction), cause agglutination (clumping) into insoluble complexes that are ingested by phagocytes, or neutralize pathogens.
34
_Cell-surface antibodies_ can
_activate immune cells_ or _mediate allergic reactions._
35
_Memory B-cells_ lie in wait for a
_second exposure_ to a pathogen and can then mount a more rapid and vigorous immune response (_secondary response_).
36
_Cell-mediated_ (cytotoxic) immunity is centered on the functions of
**T-cells**
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**T-cells** undergo maturation in the _thymus_ through
_positive selection_ (only selecting for T-cells that can react to antigen presented on MHC) and _negative selection_ (causing apoptosis in self-reactive T-cells).
The _peptide hormone:_ **thymosin** promotes T-cell development.
38
**Helper T-cells** (Th or CD4+) respond to antigen on
MHC-II and coordinate the rest of the immune system, secreting lymphokines to activate various arms of immune defense.
Th1 cells secrete interferon gamma, which activates macrophages.
Th2 cells activate B-cells, primarily in parasitic infections.
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**Cytotoxic T-cells** (Tc, CTL, or CD8+) respond to antigen on
MHC-I and kill virally infected cells.
40
**Suppressor (regulatory) T-cells** (Treg) tone down the
_immune response after an infection_ and _promote self-tolerance._
41
_Memory T-cells_ serve a similar function to \_\_\_\_\_.
**Memory B-cells.**
42
In **autoimmune conditions**, a _self-antigen_ is identified as
_foreign_, and the immune system attacks the body’s own cells.
43
In allergic reactions,
nonthreatening exposures incite an inflammatory response.
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**Immunization** is a method of inducing
_active immunity_ (activation of B-cells that produce antibodies to an antigen) prior to exposure to a particular pathogen.
\*there is _active immunity_ and _passive immunity_
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_Passive immunity_ is the transfer of
antibodies to an individual.
\*there is active immunity and passive immunity
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The Lymphatic System
START
The **immune system** and the l**ymphatic system** are intimately related.
**Structure:**
The _lymphatic system_, along with the _cardiovascular system_, is a type of circulatory system. It is made up of one-way vessels that become larger as they move toward the center of the body. These vessels carry _lymphatic fluid (lymph)_ and most join to form a large thoracic duct in the _posterior chest,_ which then delivers the fluid into the left subclavian vein (near the heart).
_Lymph nodes_ are small, bean-shaped structures along the _lymphatic vessels_. **Lymph nodes** _contain_ a **lymphatic channel**, as well as an _artery_ and a _vein_. The lymph nodes provide a space for the cells of the immune system to be exposed to possible pathogens.
**Function:**
The **lymphatic system** serves many different purposes for the body by providing a ***_secondary system for circulation._***
**Equalization of Fluid Distribution:**
At the capillaries, fluid leaves the bloodstream and goes into the tissues. The quantity of fluid that leaves the tissues at the arterial end of the capillary bed depends on both **hydrostatic** and **oncotic pressures** **_(Starling forces)_**. Remember that the _oncotic pressure_ of the blood draws water back into the vessel at the venule end, once _hydrostatic pressure_ has decreased. Because the net pressure drawing fluid in at the venule end is slightly less than the net pressure pushing fluid out at the arterial end, a small amount of fluid remains in the tissues. _Lymphatic vessels_ drain these tissues and subsequently return the fluid to the bloodstream.
The **lymphatics** offer some protection against pathology. For example, if the blood has a low concentration of albumin (a key plasma protein), the **oncotic pressure** of the blood is decreased, and less water is driven back into the bloodstream at the venule end. Thus, this fluid will collect in the tissues. Provided that the lymphatic channels are not blocked, much of this fluid may eventually return to the blood-stream via the lymphatics. Only when the lymphatics are overwhelmed does **_edema_ occur**—_swelling due to fluid collecting in tissue._
**Transportation of Biomolecules:**
The _lymphatic system_ also transports fats from the digestive system into the blood-stream. Lacteals, small lymphatic vessels, are located at the center of each villus in the small intestine. Fats, packaged into chylomicrons by intestinal mucosal cells, enter the lacteal for transport. Lymphatic fluid carrying many chylomicrons takes on a milky white appearance and is called chyle.
**Immunity:**
As stated previously in this chapter, **_lymph nodes_** are a place for _antigen-presenting cells_ and _lymphocytes_ to interact. B-cells proliferate and mature in the lymph nodes in collections called **germinal centers.**
47
The lymphatic system is a
circulatory system that consists of one-way vessels with intermittent lymph nodes.
48
The **lymphatic system** connects to the **cardiovascular system** via the
**_thoracic duct_** in the _posterior chest._
49
The lymphatic system equalizes
fluid distribution, transports fats and fat-soluble compounds in chylomicrons, and provides sites for mounting immune responses.
50
1� What are the differences between **_innate_** and **_adaptive immunity_**?
* Innate immunity:
* Adaptive immunity:
1. **Innate immunity** consists of defenses that are always active against pathogens, but that are not capable of targeting specific invaders.
It takes longer to mount a response with **adaptive immunity**, but the response targets a specific pathogen and maintains immunologic memory of the infection to mount a faster response during subsequent infections.
51
2. Compare and contrast B-and T-cells:
CHART:
1. Both B-cells and T-cells _develop in the_ **bone marrow**
2. B-cells mature in :bone marrow (but are activated in spleen or lymph bodes)
T-cells mature in: Thymus
3. B-cells major function: produce antibodies
T-cells major fuction: Coordinate immune system and directly kill infectted cells
4. B-cells and T-cells: are both specific (NOT non-specific)
5. B-cell: Humoral
T-cell: Cell-mediated
52
3� Which cells are considered granulocytes? Which are considered agranulocytes?
• Granulocytes:
• Agranulocytes:
Site
3. **Granulocytes** include _neutrophils, eosinophils, and basophils._
**Agranulocytes** include _B-_and _T-cells (lymphocytes)_ and _monocytes (macrophages)._
53
1� For each of the *_noncellular nonspecific immune defenses_* listed below, provide a brief description of its immunologic function:
* Skin:
* Defensins:
* Lysozyme:
* Mucus:
* Stomach acid:
* Normal gastrointestinal flora:
* Complement:
**Skin** provides a _physical barrier_ and s_ecretes antimicrobial enzymes._
**Defensins** are examples of _antibacterial enzymes on the skin._
**Lysozyme** is _antimicrobial_ and is _present in tears and saliva._
**Mucus** is present on _mucous membranes_ and _traps incoming pathogens_; in the respiratory system, _cilia_ propel the mucus upward so it can be _swallowed or expelled._
**Stomach acid** is an _antimicrobial substance_ in the _digestive system._
The **normal gastrointestinal flora** provides competition, making it hard for _pathogenic bacteria_ to grow in the _gut_.
**Complement** is a set of proteins in the blood that can create holes in bacteria.
54
2� Which cells are _professional antigen-presenting cells_?
2. Professional antigen-presenting cells include:
1. macrophages
2. dendritic cells in the skin
3. some B-cells
4. certain activated epithelial cells
55
3� What are the differences between _MHC-I_ and _MHC-II_?
* MHC-I:
* MHC-II:
3. MHC-I is found in all nucleated cells and presents pieces of proteins (peptides) created within the cell (endogenous antigens); this can allow for detection of cells infected with intracellular pathogens (especially viruses).
MHC-II is only found in antigen-presenting cells and presents proteins that result from the digestion of extracellular pat4. Natural killer cells are activated by cells that do not present MHC (such as virally infected cells and cancer cells).
Neutrophils are activated by bacteria, especially those that have been opsonized (tagged with an antibody on their surface).
Eosinophils are activated by invasive parasites and allergens.
Basophils and mast cells are activated by allergens.
56
4� What stimulus activates each of the following types of cells?
* Natural killer cells:
* Neutrophils:
* Eosinophils:
* Basophils and mast cells:
4. **Natural killer cells** are activated by cells that do not present MHC (such as virally infected cells and cancer cells).
**Neutrophils** are activated by bacteria, especially those that have been opsonized (tagged with an antibody on their surface).
Eosinophils are activated by _invasive parasites_ and _allergens._
Basophils and _mast cells_ are activated by allergens.
57
1� For each of the _lymphocytes_ listed below, what are its main functions?
* Plasma cell:
* Memory B-cell:
* Helper T-cell:
* Cytotoxic T-cell:
* Suppressor (regulatory) T-cell:
* Memory T-cell:
1. **Plasma cells** form from B-cells exposed to antigen and produce antibodies.
Memory B-cells also form from B-cells exposed to antigen and lie in wait for a second exposure to a given antigen to mount a rapid, robust response.
Helper T-cells coordinate the immune system through lymphokines and respond to antigen bound to MHC-II.
Cytotoxic T-cells directly kill virally infected cells and respond to antigen bound to MHC-I.
Suppressor (regulatory) T-cells quell the immune response after a pathogen has been cleared and promote self-tolerance.
Memory T-cells, like memory B-cells, lie in wait until a second exposure to a pathogen to mount a rapid, robust response.
58
2� What are the three main effects circulating antibodies can have on a pathogen?
•
•
•
2. Circulating antibodies can mark a pathogen for destruction by phagocytic cells (opsonization), cause agglutination of the pathogen into insoluble complexes that can be taken up by phagocytic cells, or neutralize the pathogen by prevent-ing it from invading tissues.
59
3� How do antibodies become specific for a given antigen?
3. B-cells originally mature in the bone marrow and have some specificity at that point; however, antibodies that can respond to a given antigen undergo hyper-mutation, or rapid mutation of their antigen-binding sites. Only those B-cells that have the highest affinity for the antigen survive and proliferate, increasing the specificity for the antigen over time.
60
4� A T-cell appropriately passes through positive selection, but then inappropri-ately passes through negative selection. What will this T-cell be reactive toward?
4. Positive selection occurs when T-cells in the thymus that are able to respond to antigen presented on MHC are allowed to survive (those that do not respond undergo apoptosis). Negative selection occurs when T-cells that respond to self-antigens undergo apoptosis before leaving the thymus. A T-cell that appropriately passes through positive selection, but then inappropriately passes through negative selection will be reactive to self-antigens.
61
5� Which cells account for the fact that the secondary response to a pathogen is much more rapid and robust than the primary response?
5. Memory cells allow the immune system to carry out a much more rapid and robust secondary response.
62
6� What is the difference between active and passive immunity?
* Active immunity:
* Passive immunity:
6. Active immunity refers to the stimulation of the immune system to produce antibodies against a pathogen. Passive immunity refers to the transfer of anti-bodies to prevent infection, without stimulation of the plasma cells that produce these antibodies.
63
1� Filariasis is the name for an infection with a member of a certain group of parasites, most notably Wuchereria bancrofti� This parasite resides in lymph nodes and causes blockage of flow. If an individual had a W. bancrofti infection in the lymph nodes of his or her thigh, what would likely happen?
1. Fluid would be unable to return from the lower leg, and edema would result. This infection leads to elephantiasis, severe swelling of the limb with thickening of the skin.
64
2� What structure is primarily responsible for returning materials from lymphatic circulation to the cardiovascular system?
2. The thoracic duct carries lymphatic fluid into the left subclavian vein.
