12.6 The Specific Immune System Flashcards
Introduction to ‘The Specific Immune System’.
- All cells have antigens on their surface
* Body can differentiate between self-antigens, on your cells, and non-self antigens, on pathogen cells
What do antigens do?
Trigger an immune response, involving production of polypeptides called antibodies
How does the specific immune system compare to the non-specific responses?
The specific immune system is slower - can take 2 weeks to respond to pathogens.
However, immune memory cells react rapidly to a second invasion of the same pathogen.
What are antibodies?
Y-shaped glycoproteins called immunoglobulins.
What do antibodies do?
Bind to specific antigens on pathogens/toxins which triggered the immune response.
What is the relationship between antigens and antibodies?
There’s a specific antibody for each antigen.
What is the structure of antibodies?
Made up of 4 chains:
2 long polypeptide chains = heavy chains
2 short polypeptide chains = light chains
What are the chains making up an antibody held together by?
Disulfide bridges.
*disulfide bridges are also present within the chains, keeping their shape the same
How do antibodies bind to antigens?
Through a lock-and-key mechanism, similar to how an enzyme’s active site binds to complementary substrate.
What is the antigen’s binding site?
An area of 110 amino acids on both heavy + light chains, known as the variable region.
What gives an antibody its specificity to an antigen?
The shape of the variable region.
What is the constant region of an antibody?
The rest of the antibody which doesn’t change shape.
What is the name of the product formed after an antibody binds to an antigen?
Antigen-antibody complex
What are the 4 ways in which antibodies defend the body?
- Antibody of A-AC acts as opsonin - complex is easily engulfed and digested
- Once pathogens are part of the A-AC, they can no longer invade host cells
- Antibodies act as agglutinins - cause pathogens carrying A-AC to clump together:
= Easier for phagocytes to engulf many pathogens at one time
= Prevents them from spreading even more throughout the body - Antibodies act as anti-toxins, binding to toxins produced by pathogens and neutralizing them
What 2 types of white blood cells make up the specific immune system?
B-lymphocytes
T-lymphocytes
Where are B-lymphocytes produced?
Bone marrow
Where are T-lymphocytes produced?
Thymus gland
What are the 4 main types of T-lymphocytes?
T-helper cells
T-killer cells
T-memory cells
T-regulator cells
What is the structure and function of the structure of T helper cells?
CD4 receptors on plasma membrane, which bind to surface antigens on APCs.
What do T helper cells produce?
Interleukins, a type of cytokine.
What are the 3 functions of the interleukins produced by T helper cells?
- Stimulate activity of B cells. This increases antibody production.
- Stimulates production of other T cells
- Stimulates macrophages to ingest pathogens with the Antigen-Antibody Complexes
What is the function of T killer cells?
To destroy pathogens carrying the antigen
What chemical do T killers produce? What is the function of this chemical?
Perforin - Kills pathogen, by making holes in cell membrane making it freely permeable
What are T-memory cells a part of?
Immunological memory.
What happens when T memory cells meet an antigen for the second time?
They divide rapidly to produce huge amounts of clones of T killer cells that destroy the pathogen
What do T regulator cells do?
Suppress the immune system as they control and manipulate it.
Stop immune response after pathogen is destroyed.
Ensure the body recognizes self-antigens and doesn’t trigger an autoimmune response (interleukins play an important role in this control)
What are the 3 main types of B-lymphocytes?
Plasma cells
B effector cells
B memory cells
What is the function of plasma cells?
Produce antibodies for a particular antigen and release them into the circulation
How long do plasma cells live?
A few days
While a plasma cell is alive and active, what is the rate at which it produces antibodies?
2000 antibodies/s
What is the function of B effector cells?
Divide to form plasma cell clones
What is the function of B memory cells?
Live for a long time and provide immunological memory.
They remember a specific antigen and enable the body to rapidly respond the next time a pathogen carrying the antigen appears
What happens in cell-mediated immunity?
T lymphocytes respond to cells of an organism that have changed in some way, e.g. a virus infection, through antigen processing or mutation (cancer cells) and to cells from transplanted tissue.
What are the 2 main stages of the cell mediated response?
- In non-specific defence system, macrophages engulf + digest pathogens during phagocytosis.
They process antigens from pathogen’s cell surface to form APCs, Antigen-Presenting Cells - Receptors on T helpers fit the antigens. These T helpers become activated and produce interleukins, which stimulate T cells to divide rapidly through mitosis. They form clones of identical activated T helpers that carry the specific antigen to bind to a pathogen.
In the cell mediated immunity response, what 4 things can the cloned T cells do?
- Develop into T memory cells, producing a rapid response when pathogen present for the second time
- Produce interleukins that stimulate phagocytosis
- Produce interleukins that stimulate B cells to divide
- Develop into T killer cells and destroy infected cells
What happens in humoral immunity?
Body responds to antigens found outside of cells (bacterial, fungal etc) and to APCs.
What does the humoral immune system produce?
Antibodies soluble in blood and tissue fluid and aren’t attached to cells
What do B-lymphocytes have on their cell-surface membranes?
Antobidies
How many types of B-lymphocytes are there? What’s special about them
Millions. Each B-lymphocyte has a different antibody
How do B-lymphocytes react when a pathogen enters the body?
A specific B cell with a complementary antibody will bind to it, engulf it and the antigen becomes an APC
What are the 5 stages of Humoral Immunity?
- Activated T helpers bind to B cell APC.
This is called clonal selection: point at which B cell w/ correct antibody to destroy pathogen is selected for cloning - Interleukins produced by activated T helpers activate the B cells
- Activated B cells divide by mitosis to form clones of plasma cells and B memory cells. This is Clonal Expansion
- Cloned plasma cells that produce antibodies that fit antigens on pathogen’s surface bind to antigens and disable them or act as opsonins/agglutinins.
- This is the primary immune response (can take days to weeks to become fully effective against pathogens. - Some cloned B cells develop into B memory cells.
In relation to humoral immunity, why do we get ill?
The symptoms are the result of pathogens dividing inside our body before the primary response kicks in
What happens if the same pathogen enters the body for the second time?
B memory cells divide to rapidly form plasma cell clones.
When a pathogen enters the body for the second time, what is the function of B memory cells rapidly dividing to form plasma cell clones?
Cloned plasma cells produce the right antibodies and destroy a pathogen quickly before symptoms of a disease show. This is the secondary immune response.
What is an ‘Autoimmune Disease’?
Occurs when the immune system stops recognising self cells and starts attacking healthy body tissue
What are some of the causes for the autoimmune disease?
- Genetic tendency in families
- Immune system reacts abnormally to a mild pathogen
- T regulators stop working effectively
What is the function of immunosuppressants?
Used as treatment against autoimmune disease - they prevent the immune system working.
What is the down side to immunosuppressant drugs?
They deprive the body of natural defences against communicable diseases
What are the 3 common autoimmune diseases?
- Type 1 diabetes
- Rheumatoid arthritis
- Lupus
What body part does type 1 diabetes affect?
Insulin-secreting cells of pancreas
What treatments are there for type 1 diabetes?
- Insulin injections
- Pancreas transplants
- Immunosuppressants
What body parts does rehumatoid arthritis affect?
Joints - mainly in hands, wrists, ankles and feet
Can rheumatoid arthritis be cured? If not, what can be used to ease the symptoms?
NO CURE • Anti-inflammatory drugs • Steroids • Immunosuppressants • Pain relief
What body parts does lupus affect?
Often skin and joints - causes fatigue
• Can attack any organ in the body, including kidneys, liver, lungs or brain
Can lupus be cured? If not, what can be used to ease the symptoms?
NO CURE
- Anti-inflammatory drugs
- Steroids
- Immunosuppressants
