The specific immune system Flashcards
(35 cards)
1
Q
What is specific immunity?
A
- Also known as active immunity or acquired immunity
- The immune system ‘remembers’ an antigen after an intial response leading to an enhanced response to subsequent encounters
- It involves specialised cells called lymphocytes which recognise specific antigens
2
Q
What is the primary specific immune response?
A
The response of the immune system the first time it is exposed to an antigen
3
Q
What is the secondary specific immune response?
A
The response of the immune systm the second and subsequent times it is exposed to an antigen
4
Q
What occur in the first exposure of the specific immune system?
A
- Clonal selection
- Clonal expansion/proliferation
- Clonal differentiation
5
Q
What occurs in clonal seletcion?
A
- It is when the exposure to a specific antigen selectively stimulates the proliferation of the cell with the appropriate antibody to form numerous clones of thse specific antibody-forming cells
- Lymphocyte with complementary cell-surface receptor to the antigen binds
- All other lymphocytes are blind
6
Q
What occurs in clonal expansion?
A
- The mas proliferation of antibody-producing cells by clonal selection
- Lymphocyte with complementary cell-surface receptor to the antigen clones and grows in number by mitosis and cell division
7
Q
What occurs in clonal differentiation?
A
- Some clones differentiation into cells that carry out the function of the lymphocyte
- For example, B cells may differentiate into plasma cells or T cells may become activated
- Some clones differentiate into memory cells
- B or T cells may differentiate into memory cells
8
Q
What occurs during the second exposure?
A
- Memory cells present divide rapidly on next encounter of antigen
- Heightened response - rapid elimination of antigen
9
Q
What are the two types of lymphocytes? What are their roles? And where do they mature?
A
- B lymphocytes carry out the humoral response and become APCs which is recognised by T helper cells
- They mature in the bone marrow
- T lymphocytes carry out the cell-mediated response by attaching to APCs
- They mature in the thymus gland
10
Q
What are the different types of T lymphocytes?
A
- T helper cells
- T killer cells
- T memory cells
- T regulator cells
11
Q
What is the role of T helper cells?
A
- T lymphocytes CD4 receptors on their plasma membranes, which bind to the MHC (antigen) on APCs
- They produce interleukins which are a type of cytokine
- The interleukins stimulate the poliferation and differentiation of all lymphocytes and phagocytes of the non-specific immune response (macrophages and neutrophils)
12
Q
What is the role of T killer cells?
A
- T lymphocytes that destroy pathogens carrying a specific antigen
- They produce a chemical called perforin, which kills pathogens by making holes in the plasma membrane so it is freely permeable
13
Q
What is the role of T memory cells?
A
- T lymphocytes that live for a long time and are part of the immunological memory
- If they meet an antigen a second time, they divide rapidly to form a huge number of clones of T killer cells that destroy the pathogen
14
Q
What is the role of T regulator cells?
A
- T lymphocytes that surpress and control the immune system
- They the immune response once a pathogen has been destroyed
- It makes sure that the body recognises self antigens and prevents an autoimmune response
15
Q
What are the different types of B lymphocytes?
A
- Plasma cells
- B effector cells
- B memory cells
16
Q
What is the role of plasma cells?
A
- B lymphocytes that produces 2000 antibodies to a particular antigen every second and release them into circulation
- It only lives for a few days
17
Q
What is the role of B effector cells?
A
B lymphocyes that divide to form plasma cell clones
18
Q
What is the role of B memory cells?
A
- B lymphocytes that live for a very long time and provide the immunological memory
- They are programmed to remember a specific antigen and enable the body to make a very rapid response
when a pathogen carrying that antigen is encountered again
19
Q
When does the cell mediated response occur?
A
Defends against transplanted tissue and when the body is infected with viruses, intracellular bacteria or cancer cells
20
Q
What occurs in the cell mediated response?
A
- In the non-specific defence system, macrophages engulf and digest pathogens in phagocytosis. They process the antigens from the surface of the pathogen to form antigen-presenting cells (APCs)
- The receptors on some of the T helper cells fit the antigens (cloncal selection). These T helper cells become activated and produce interleukins, which
stimulate more T cells to divide rapidly by mitosis. They form clones of identical activated T helper cells that all carry the right antigen to bind to a particular pathogen - The cloned T cells may:
- develop into T memory cells, which give a rapid response if this pathogen invades the body again
- produce interleukins that stimulate phagocytosis (activate macrophages and neutrophils)
- produce interleukins that stimulate B cells to divide
- produce interleukins that activate T killer cells and stimulate the development of a clone of active and memory T killer cells that are specific for the presented antigen on infected cells and then destroy them. When the body is infected again the memory T killer cells become activated
21
Q
When does the humoral response occur?
A
It responds to antigens found outside the cells, for example bacteria and fungi and to APCs
22
Q
What occurs in the humoral response?
A
- Activated T helper cells bond to the B cell APC. This is clonal selection
- Interleukins produced by the activated T helper cells activate the B cells
- The activated B cells divides by mitosis to give clones of plasma cells and B memory cells. This is clonal expansion
- Cloned plasma cells produce antibodies that fit the antigens on the surface of the pathogen, bind to the antigens and disable them,
or act as opsonins or agglutinins. This is the primary immune response and it can take days or even weeks to become fully effective against a particular pathogen. This is why we get ill - the symptoms are the result of the way our body reacts when the pathogens are dividing freely, before the primary immune response is fully operational - Some cloned B cells develop into B memory cells. If the body is infected by the same pathogen again, the B memory cells divide rapidly to form plasma cell clones. These produce the right antibody and wipe out the pathogen very quickly, before it can cause the symptoms of disease. This is the secondary immune response.
23
Q
What is an autoimmune disease?
A
A condition or illness resulting from an autoimmune respone
24
Q
What is an autoimmune response?
A
A response when the immune system acts against its own cells and destroys healthy tissue in the body
25
What are agglutinins?
- Chemicals (antibodies) that cause pathogens to clump together so they are easier for phagocytes to engulf and digest
- This slows the spread of the pathogen facilitating phagocytosis
26
What are antitoxins?
Chemicals (antibodies) that binds to toxins produced by pathogens so they no longer have an effect
27
What are some examples of autoimmune diseases?
- Type 1 diabetes
- Rheumatoid arthritis
28
What is the issue with immunodepressant drugs?
They prevent the immune system from working, depriving the body of its natural defences against communicable diseases
29
What body part does rheumatoid arthritis affect? And what is the treatment?
Affected body part:
- Joints => especially in the hands, wrists, ankles and feet
Treatment:
- no cure
- anti-inflammatory drugs
- steroids
- immunosuppressants
- pain relief
30
What body part does type 1 diabetes affect? And what is the treatment?
Affected body part:
- The insulin-secreting cells of the pancreas
Treatment:
- insulin injections
- pancreas transplants
- immunosuppressants
31
What are antibodies?
- Y-shaped glycoproteins called immunoglobins
- Produced and secreted into the blood by plasma cells (B lymphocytes) of the immune system in response to the presence of a foreign antigen
- They bind to a specific antigen on the pathogen or toxin that has triggered the immune response
32
What is antigen-antibody complex?
The complex formed when an antibody binds to an antigen
33
What is the structure of antibodies?
- Made up of 4 polypeptide chains
- It is made up of 2 long polypeptide chains called the heavy chains and 2 much shorter identical chains called the light chains
- The chains are held together by disulfide bridges within the polypeptide chains
**_HAS THREE REGIONS_**
Constant region:
- All Abs have the same 1° structure => same 3° structure
- Contains binding site for leukocytes e.g. neutrophils or T cells
Variable region:
- Unique Ag binding site: specific 1° structure => specific 3° structure
- Complementary shape to one specific Ag
- Each Ab can bind to 2 identical Ag molecules
Hinge region:
- Allows flexibility and movement of variable regions => increases Ag binding potential
34
What are the roles of antibodies?
- Opsonisation
- Agglutination
- Anti-toxins
35
How do antibodies defend the body?
1) The antibody of the antigen-antibody complex acts as an opsonin so the complex is easily englufed and digested by phagocytes
2) Most pathogens can no longer effectively invade the host cells once they are apart of the antigen-antibody complex
3) Antibodies act as agglutinins causing pathogens carrying antigen-antibody complexes to clump together. This prevents them from spreading through the body and makes it easier for phagocytes to engulf a number of pathogens at the same time
4) Antibodies can act as antitoxins, binding to the toxins produced by pathogens and making them harmless
