Immune System Flashcards
(45 cards)
1
Q
Why do microorganisms want to infect us?
A
We have lots of water, proteins, nutrients, and a warm environment that they thrive in
2
Q
What are some possible pathogens?
A
Viruses, bacteria, single-called eukaryotic parasites (yeast), parasitic worms, and maggots
3
Q
What is the immune system?
A
A set of mechanisms that protect an organism from infection by identifying and killing pathogens
4
Q
What is an autoimmune disease?
A
When your immune system attacks the host’s good cells
5
Q
Why is it important that the immune system is adaptive?
A
Because pathogens are constantly evolving in order to avoid detection
6
Q
What are the two types of defense mechanisms?
A
Innate and adaptive immunity
7
Q
What is innate immunity?
A
A defense active immediately upon infection; includes barrier defenses; is constantly active and does not require activation, is not specific, and stops any foreign substance
8
Q
What is adaptive immunity?
A
- Defense that is activated after the innate response and develops more slowly (because they take time to identify foreign substance)
- Is specific to certain objects and much be activated when in contact with pathogens
- Only needs to recognize something once for it to be immune for life
9
Q
What makes up innate immunity?
A
- Recognizes traits shared by broad ranges of pathogens using a set of receptors
- is a rapid response
- Barrier defenses: skin, mucous membrane, and secretions
- Internal Defenses: phagocytes cells (phagocytosis), natural killer cells, antimicrobial proteins/peptides, and inflammatory response, and interferons
10
Q
What makes up adaptive immunity?
A
- Recognizes traits specific to particular pathogens using a vast array of receptors
- Is a slower response
- Humoral response: antibodies defend against infections in body fluids
- Cell-mediated response: cytotoxic cells defend against infection in body cells
11
Q
[ADAPTIVE] What is a humoral response?
A
Responses through body fluids; protects for pathogens outside of the cell
12
Q
[ADAPTIVE] What is a cell-mediated response?
A
Controlled by t-cells which kills pathogens
13
Q
Why is bone marrow so important?
A
It contains essential cells such as multi potent cells which branches into two different types of cells necessary for immunity
14
Q
What are multipotent cells?
A
- Special cells in bone marrow that have stem cells (stem cells are able to keep replicating of which its progeny can differentiate into different cells)
- Gives rise to myeloid (red/white blood cells and platelets) and lymphoid (branches into 3 more lymphocyte cells)
15
Q
What cells are made from myeloid cells?
A
-Red/white blood cells and platelets
- Granular cells: basophils, eosinophils, neutrophils, mast cells
Agranular cells: monocytes, macrophages, dendritic cells
16
Q
What is made from lymphoid cells?
A
B lymphocytes, T lymphocytes, and natural killer cells
B AND T LYMPHOCYTES ARE THE ONLY CELLS APART OF ADAPTIVE IMMUNITY - EVERYTHING ELSE IS INNATE
17
Q
[INNATE] What are the barrier defenses?
A
- Include skin and mucous membranes of the digestive, respiratory, urinary, and reproductive tracts
- Mucus is used to trap and allow for the removal of microbes
- Body fluids including saliva, mucus, and tears are hostile to many microbes
~ Have anti-microbial compounds that decrease the
number of pathogens (ex. Lysozymes)
~ Body fluids help to wash away pathogens, preventing colonization of microorganisms - Low pH of skin and digestive system prevents growth of many bacteria
18
Q
[INNATE] What are cellular innate defenses?
A
- Innate immune cells in mammals detect, devour, and destroy invading pathogens
- These cells recognize groups of pathogens using TLRs or Toll-like receptors
~ Recognize fragments of molecules characteristic of a set of pathogens
~ Some are found on the surface of cells and stick out; they attack pathogens in extracellular fluid
19
Q
[INNATE] What are the types of phagocytes cells?
A
2 MAIN TYPES:
- Neutrophils: circulate the blood
~Most abundant in the white blood cells; are the first on
site
- Macrophages: migrate through the body or reside permanently in organs and tissues
2 ADDITIONAL TYPES:
- Dendritic cells: stimulate development of adaptive immunity
~Found in tissues that are exposed environments like skin or mucus; are already ready there and waiting to be activated
- Eosinophils: discharge destructive enzymes against parasites
~ Explodes all killing substance around it once activated
ALL PHAGOCYTES ARE ABLE TO MOVE WHERE THEY WANT TO GO
20
Q
[CELLULAR INNATE] What are natural killer cells?
A
- Circulate through the body and detect abnormal cells
- Release chemicals leading to cell death, inhibiting the spread of virally infected or cancerous cells
~Does not undergo phagocytosis but rather kills with chemicals - Involve the lymphatic system (in addition with other innate defenses as well)
21
Q
What is the lymphatic system and what does it consists of?
A
- Is a draining system that collects fluid from all over the body and puts it into the bloodstream
- Immunity is mediated by the lymphatic system
~ lymph nodes and spleen (screens for blood for the presence of infection) is packed with immune cells; when lymph fluid flows through lymph nodes (through the outer surface of lymph nodes) it causes the liquid to get check by immune cells - Lymphatic system is similar to the circulatory system but uses pumps instead of vessels
- Lymphatic system helps bring liquid from the capillaries (that escaped due to pressure of blood being constricted by blood) back into the bloodstream
- Capillaries have the most gas and material (waste, nutrients) exchange between the blood and external environment
22
Q
[INNATE] What makes up the antimicrobial peptides and proteins?
A
- Peptides and proteins function in innate defense by
attacking pathogens or impeding their reproduction - Peptides insert themselves in to the membrane of the bacteria so that the cell is flooded by liquid and explodes
- Interferon proteins provide innate defense by interfering with viruses and helping activate macrophages
~ tells neighboring cells that a virus infection is going on causing the neighbor cells to increase resistance
~ recombinant DNA is used to make interferons - About 30 proteins make up the complement system, which causes lysis of invading cells and helps trigger inflammation
~ complement system is made up of a family of proteins which circulate in body fluids in an inactive state (due to the absence of pathogens); once activated, one will turn another one until there is a cascade, creating a pore in the plasma membrane of the pathogen and killin git
23
Q
[INNATE] What is the inflammatory response?
A
- Brought about by molecules released upon injury or infection; is the body’s response to injury or infections
- Purpose of inflammation is to isolate the area and prevent the infection from spreading all while recruiting cells to kill the foreign cells and promote healing
- Mast cells (immune cells in connective tissue) release histamine, which triggers blood vessels to dilate and become more permeable
~ Are very abundant under the skin and the lining of organs; when they detect infection, they degranulate and release cells of which cause vessels to dilate so that more white blood cells can enter into the area of infection
24
Q
[INNATE] What makes up the process of inflammation?
A
- In the presence of injury, mast cells release histamine which diffuses locally and causes the vessels and capillaries to dilate and become more accessible to the place of injury
- Macrophage releases signaling molecule which then attract neutrophils and antimicrobial peptides to enter the tissue and start phagocytosis
- While all this happens, the complement system continues to attract more immune cells
- When the bacteria are all gone, all signaling will stop and the damage cells will release growth factors to allow a healing
25
[INNATE] How are pathogens able to escape the innate immunity?
- Some pathogens are sneaky by modifying their surface or by resisting break down following phagocytosis
- Streptococcus pneumonia is a bacterium that does just this; is the major cause for meningitis and pneumonia
26
[ADAPTIVE] What two immune responses make up the adaptive immune system?
- Humoral immune response: fluid that protects against pathogens
~creates B cells which then form antibodies that kill extracellular pathogens
- Cellular immune response: important for pathogens in the cell (intercellular)
~creates cytotoxic T cells which kills virus infected/cancer cells (intracellular immunity)
27
[ADAPTIVE] What lymphocytes are in the adaptive system and why are they important?
- Lymphocytes are white blood cells and consists of two types
~ T-cells: mature in the thymus above the heart
-(first comes from bone marrow into the thymus)
~ B-cells: mature in the bone marrow
-Adaptive is highly specific which means that is can make a lot of receptors for pathogens
28
[ADAPTIVE] What are the structure differences between a mature B cell and a mature T cell?
- B cells have antigen receptors that are wide structures (2 branches)
- T cell antigen receptors only have a single branch and is rather simple
29
[ADAPTIVE] What is an epitope of a B or T cell antigen receptor?
- Are small portions of the antigens that bind to the receptors instead of the entire antigen
- Each individual B or T cell will recognize only ONE epitope; this makes the adaptive immunity incredibly specific
* Antibodies react with antigenic determinants
30
[ADAPTIVE] What makes up a B cell antibody? (Aka what is its structure?)
- Each B cell antigen receptor is a Y-shaped molecule with two identical heavy chains and two identical light chains
~ Heavy chains: are the longer polypeptide chain of the antibody where there the variable (V) regions is on the tip while the constant (C) region makes up the majority of the lower-half of the structure; is connected to the other heavy chain via a disulfide bridge
~ Light chains: the shorter polypeptide chain of the antibody that has equal proportions of the V and C regions (V is at the tip); is connected to the heavy chain via disulfide bridge
- Variable region: amino acid sequence is highly variable and is different from one antibody to another; provides specificity for the antibody
- Constant region: amino acid sequences are very similar; are very conserved so it determines which class of antibody it is part of and what its functions are
31
[ADAPTIVE] What happens during B cell activation (aka they have bounded properly to an antigen?)
- When a B cell antigen receptor binds to an antigen this is considered the early step of B cell activation
- This binding gives rise to cells that secrete a soluble form of the receptor called an antibody or immunoglobulin (Ig)
- Antibodies also have a Y shape but are secreted, not membrane bound
- When B cells are activated, they can proliferate and carry out the function of the humoral immune system
~ Gives rise to a huge number of identical cells (all with the same V regions and function) of which will differentiate into plasma cells (effector cells: carry out of the effect freely, not membrane bound) *plasma cells can secrete 1000s of antibodies per second*
- Antibodies can bind to its target whether or not its on a cell’s surface or detached
32
[ADAPTIVE] How do T-Cells recognize antigens and what is its structure?
- Unlike B cells, T cells have a much simpler structure with only two polypeptide chains (alpha and beta) binded by a disulfide bridge; alpha is larger
~Tips are V region while rest is C region
- T and B cells are different because T cell receptors can only bind to antigen fragments that have been processed then displayed by MHC proteins
-
33
[ADAPTIVE] What is the major histocompatibility complex and what is the difference between Class I and Class II?
- MHCs are plasma membrane glycoproteins
~Functions to display antigens
~Expressed on the surface of the cells
- A host takes in a pathogen and breaks down its antigen fragments inside itself. Taking one of the fragments, the MHC molecules takes the fragment out and displays it externally for the T cell to bind to
- Class I MHC proteins: present on the surface of every nucleated cell BUT the blood cells
- Class II MHC proteins: found mostly on surfaces of B cells, dendritic cells, and macrophages (antigen-presenting cells)
34
[ADAPTIVE] Why are MHCs important for T cells?
- T cell receptors can only bind to antigen fragments displayed or presented on MHC molecules
~T cell receptor must bind to both the antigen fragment and MHC molecule
- In infected cells, MHC molecules bind and transport antigen fragments to the cell surface, this is called antigen presentation
35
[ADAPTIVE] How did B and T cells develop and what makes up the 4 major characteristics of the adaptive immune system?
4 Characteristics:
1. Immense diversity of lymphocytes and receptors
2. Self tolerance: lack of reactivity against an animal’s own molecules and cells
3. B and T cells proliferate after activation
4. Immunological memory
-Body can make more than 1 million B cells and more than 10 million T cell receptors, making them incredibly diverse
36
[ADAPTIVE] What is self-tolerance in immunity?
- Antigen receptors are generated by random rearrangement of DNA
~One antibody’s V region is coded differently by differing genes,
causing a huge number of specificity
- Lymphocytes in thymus are tested for self-reactivity
- B and T cells who have specific receptors for the body’s own molecules are destroyed by apoptosis (programmed cell death)
~ Roughly 90% of B and T cells are destroyed
~ This leaves the molecules that CAN fight against foreign molecules
37
[ADAPTIVE] What is the proliferation of B and T cells?
- There are few lymphocytes with antigen receptors for any particular epitope
- In lymph nodes an antigen is exposed to a steady stream of lymphocytes until a match is made
-Binding of a mature lymphocytes with its target antigen initiates events that activate the lymphocyte
~Once activated, B or T cells undergo multiple cell divisions (clinal selection) to produce a clone of identical cells
-Most cells from clone become effector cells that act immediately against the antigen
~Effector cells are plasma cells that secrete antibodies (dont live long; dies after a week)
-Remaining cells in cline become long-living memory cells that give rise to effector cells if the same antigen is encountered again
~These cells don’t do much besides wait for the antigens to present again; the memory cells can bind to the receptor and immediately proliferate
~ Enables the secondary response
-How is the correct B and T cells selected to mount an immune response? A: your body will make randomly lymphocytes with many different antigen receptors with different specificities - there are few lymphocytes against a particular epitopes (making it diverse); a lot of immune cells are packed in your lymph nodes so when your body has an infection, the first to encounter it first are the macrophages and the dendritic cells (under the skin and in the mucous membrane) they will phagocytosis the pathogen and carry it to the lymph nodes where it will displayed at the lymph nodes for the lymohocytes to be activated
38
[ADAPTIVE] What happens during immunological memory?
- Immunological memory is responsible for long term protections against diseases
- Primary Immune Response: First exposure to a specific antigen
~Develops slowly bc your antigen presenting cells do phagocytosis, then lymphocytes divide into effector and memory cells, etc. until after two weeks where it peaks in max production
-Secondary Immune Response: where memory cells facilitate a faster, more efficient response from a reservoir of T and B memory cells
~Peaks after 2 days and is usually higher than the first response
39
[ADAPTIVE] How does adaptive immunity defend against infection of body fluids and body cells?
- Humoral Immune Response (B cells): antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph
~Responsible for producing antibodies that can circulate in your body fluids until it binds to the target where it neutralizes viruses or toxins; prevents pathogens to replicate and destroys them
- Cell-Mediated Immune Response (T cells): where specialized T cells destroy affected host cells
~Calls for cytotoxic cells to recognize the infected cells int he body and kill them
-Both humoral and cell-mediated include primary and secondary immune responses
40
[ADAPTIVE] What are helper T cells and how do they help with activating adaptive immunity?
- Helper T cell: type of T cell that activates both humoral and cell-mediated immune response
~Requires the presence of a foreign molecule that can bind the antigen receptor on the helper T cell
-Antigen must be displayed on the surface of the antigen-presenting cell (extracellular proteins)
-Antigen presenting cells have Class I and II MHC molecules on their surfaces
~Class II MHC molecules provide molecular signature by which antigen-presenting cells are recognized
~APC must be macrophages, dendritic cells, or B cells
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-Antigen receptors on the surface of helper T cells bind to the antigen and the class II MHC molecule; then cytokine signals are exchanged between the two cells
~Helper T cells are then activated, proliferates, and forms a clone of helper T cells which then activate the appropriate B cells
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41
[ADAPTIVE] How are B cells formally activated?
- First begins with the activation of helper T cells, which involve the breaking down of fragments in the antigen presenting cell, the presentation of the fragment on the class II MHC on the app, then th binding of a helper T cell on this fragment, then the release of cytokines from the apc and T cell itself that causes the helper T cell to activate
- From here, the helper T cell binds to a B cell through the class II MHC molecule where it releases antigen fragments into the B cell
- The helper T cell then releases cytokines to activate the B cell and the B cell multiplies and divides into memory and plasma cells
42
[ADAPTIVE] What is the true function of an antibody?
- Antibodies do not kill pathogens but rather mark them for inactivation or destruction
- They also undergo neutralization, which is where antibodies bond to a viral surface protein, preventing infection of host cell (by preventing the virus to get in contact with its target)
- They also bind to toxins on body fluids and prevent them form entering body cells
-Opsonization: where antibodies bind to antigens on bacteria, triggering phagocytosis
~The presence of antibodies on pathogens make phagocytosis more efficient
- Antigen-antibody complexes also bind to complement proteins ,which triggers a cascade of complement protein activation
~This causes a cascade of proteins into the membrane, causing the foreign molecule to develop a pore and ultimately, lysis
43
[ADAPTIVE] What 5 forms of immunoglobulin can B cells express?
- 5 types
1. IgD (membrane bound)
2. IgA, IgE, IgG, and IgM ( soluble/secreted)
- all have same C regions in light chain regions but are different in heavy chain C regions
44
[ADAPTIVE] What do cytotoxic T cells do?
- Use toxic proteins to kill cells infected by viruses or other intracellular pathogens
- recognize fragments of foreign proteins produced by infected cells
- Activated cytotoxic T cels secretes proteins that disrupt membranes of target cells and trigger apoptosis
45
[ADAPTIVE] How are cytotoxic T cells activated?
1. First, cytokines from previously activated helper T cells help activate the cytotoxic T cells. When activated, the cytotoxic T cells are proliferated and then used to find the infected cell
2. From here, the infected cell with antigen fragments must bind to a cytotoxic T cell via their class I MHC molecule where an antigen fragment sits.
3. When the cytotoxic T cell binds to the class I MHC molecule via an antigen receptor, it also binds to the MHC with CD8, causing double binding
4. When binding is completed, the cytotoxic T cell will release perforin (form holes) and granzymes (trigger apoptosis) into the infected cell
5. Once the infected cell begins to die, the cytotoxic cell releases itself
**antigen presented is an intracellular protein fragment**
