12.6 The Specific Immune System

Question 1

Introduction to ‘The Specific Immune System’.

Answer 1

• All cells have antigens on their surface

* Body can differentiate between self-antigens, on your cells, and non-self antigens, on pathogen cells

Question 2

What do antigens do?

Answer 2

Trigger an immune response, involving production of polypeptides called antibodies

Question 3

How does the specific immune system compare to the non-specific responses?

Answer 3

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.

Question 4

What are antibodies?

Answer 4

Y-shaped glycoproteins called immunoglobulins.

Question 5

What do antibodies do?

Answer 5

Bind to specific antigens on pathogens/toxins which triggered the immune response.

Question 6

What is the relationship between antigens and antibodies?

Answer 6

There’s a specific antibody for each antigen.

Question 7

What is the structure of antibodies?

Answer 7

Made up of 4 chains:
2 long polypeptide chains = heavy chains
2 short polypeptide chains = light chains

Question 8

What are the chains making up an antibody held together by?

Answer 8

Disulfide bridges.

*disulfide bridges are also present within the chains, keeping their shape the same

Question 9

How do antibodies bind to antigens?

Answer 9

Through a lock-and-key mechanism, similar to how an enzyme’s active site binds to complementary substrate.

Question 10

What is the antigen’s binding site?

Answer 10

An area of 110 amino acids on both heavy + light chains, known as the variable region.

Question 11

What gives an antibody its specificity to an antigen?

Answer 11

The shape of the variable region.

Question 12

What is the constant region of an antibody?

Answer 12

The rest of the antibody which doesn’t change shape.

Question 13

What is the name of the product formed after an antibody binds to an antigen?

Answer 13

Antigen-antibody complex

Question 14

What are the 4 ways in which antibodies defend the body?

Answer 14

1. Antibody of A-AC acts as opsonin - complex is easily engulfed and digested
2. Once pathogens are part of the A-AC, they can no longer invade host cells
3. 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
4. Antibodies act as anti-toxins, binding to toxins produced by pathogens and neutralizing them

Question 15

What 2 types of white blood cells make up the specific immune system?

Answer 15

B-lymphocytes

T-lymphocytes

Question 16

Where are B-lymphocytes produced?

Answer 16

Bone marrow

Question 17

Where are T-lymphocytes produced?

Answer 17

Thymus gland

Question 18

What are the 4 main types of T-lymphocytes?

Answer 18

T-helper cells
T-killer cells
T-memory cells
T-regulator cells

Question 19

What is the structure and function of the structure of T helper cells?

Answer 19

CD4 receptors on plasma membrane, which bind to surface antigens on APCs.

Question 20

What do T helper cells produce?

Answer 20

Interleukins, a type of cytokine.

Question 21

What are the 3 functions of the interleukins produced by T helper cells?

Answer 21

1. Stimulate activity of B cells. This increases antibody production.
2. Stimulates production of other T cells
3. Stimulates macrophages to ingest pathogens with the Antigen-Antibody Complexes

Question 22

What is the function of T killer cells?

Answer 22

To destroy pathogens carrying the antigen

Question 23

What chemical do T killers produce? What is the function of this chemical?

Answer 23

Perforin - Kills pathogen, by making holes in cell membrane making it freely permeable

Question 24

What are T-memory cells a part of?

Answer 24

Immunological memory.

Question 25

What happens when T memory cells meet an antigen for the second time?

Answer 25

They divide rapidly to produce huge amounts of clones of T killer cells that destroy the pathogen

Question 26

What do T regulator cells do?

Answer 26

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)

Question 27

What are the 3 main types of B-lymphocytes?

Answer 27

Plasma cells B effector cells B memory cells

Question 28

What is the function of plasma cells?

Answer 28

Produce antibodies for a particular antigen and *release them into the circulation*

Question 29

How long do plasma cells live?

Answer 29

A few days

Question 30

While a plasma cell is alive and active, what is the rate at which it produces antibodies?

Answer 30

2000 antibodies/s

Question 31

What is the function of B effector cells?

Answer 31

Divide to form plasma cell clones

Question 32

What is the function of B memory cells?

Answer 32

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

Question 33

What happens in cell-mediated immunity?

Answer 33

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.

Question 34

What are the 2 main stages of the cell mediated response?

Answer 34

1. 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 2. 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.

Question 35

In the cell mediated immunity response, what 4 things can the cloned T cells do?

Answer 35

1. Develop into T memory cells, producing a rapid response when pathogen present for the second time 2. Produce interleukins that stimulate phagocytosis 3. Produce interleukins that stimulate B cells to divide 4. Develop into T killer cells and destroy infected cells

Question 36

What happens in humoral immunity?

Answer 36

Body responds to antigens found outside of cells (bacterial, fungal etc) and to APCs.

Question 37

What does the humoral immune system produce?

Answer 37

Antibodies soluble in blood and tissue fluid and aren't attached to cells

Question 38

What do B-lymphocytes have on their cell-surface membranes?

Answer 38

Antobidies

Question 39

How many types of B-lymphocytes are there? What's special about them

Answer 39

Millions. Each B-lymphocyte has a different antibody

Question 40

How do B-lymphocytes react when a pathogen enters the body?

Answer 40

A specific B cell with a complementary antibody will bind to it, engulf it and the antigen becomes an APC

Question 41

What are the 5 stages of Humoral Immunity?

Answer 41

1. 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 2. Interleukins produced by activated T helpers activate the B cells 3. Activated B cells divide by mitosis to form clones of plasma cells and B memory cells. This is Clonal Expansion 4. 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. 5. Some cloned B cells develop into B memory cells.

Question 42

In relation to humoral immunity, why do we get ill?

Answer 42

The symptoms are the result of pathogens dividing inside our body before the primary response kicks in

Question 43

What happens if the same pathogen enters the body for the second time?

Answer 43

B memory cells divide to rapidly form plasma cell clones.

Question 44

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?

Answer 44

Cloned plasma cells produce the right antibodies and destroy a pathogen quickly before symptoms of a disease show. This is the secondary immune response.

Question 45

What is an 'Autoimmune Disease'?

Answer 45

Occurs when the immune system stops recognising self cells and starts attacking healthy body tissue

Question 46

What are some of the causes for the autoimmune disease?

Answer 46

1. Genetic tendency in families 2. Immune system reacts abnormally to a mild pathogen 3. T regulators stop working effectively

Question 47

What is the function of immunosuppressants?

Answer 47

Used as treatment against autoimmune disease - they prevent the immune system working.

Question 48

What is the down side to immunosuppressant drugs?

Answer 48

They deprive the body of natural defences against communicable diseases

Question 49

What are the 3 common autoimmune diseases?

Answer 49

1. Type 1 diabetes 2. Rheumatoid arthritis 3. Lupus

Question 50

What body part does type 1 diabetes affect?

Answer 50

Insulin-secreting cells of pancreas

Question 51

What treatments are there for type 1 diabetes?

Answer 51

* Insulin injections * Pancreas transplants * Immunosuppressants

Question 52

What body parts does rehumatoid arthritis affect?

Answer 52

Joints - mainly in hands, wrists, ankles and feet

Question 53

Can rheumatoid arthritis be cured? If not, what can be used to ease the symptoms?

Answer 53

``` NO CURE • Anti-inflammatory drugs • Steroids • Immunosuppressants • Pain relief ```

Question 54

What body parts does lupus affect?

Answer 54

Often skin and joints - causes fatigue | • Can attack any organ in the body, including kidneys, liver, lungs or brain

Question 55

Can lupus be cured? If not, what can be used to ease the symptoms?

Answer 55

NO CURE * Anti-inflammatory drugs * Steroids * Immunosuppressants