Notes : 6.7 - 6.12 Immune responses

Question 1

Name the different type of barriers to entry that our body has.

Answer 1

• Stomach acid
• Skin
• Lysozyme
• Gut and skin flora inside intestines

Question 2

How can pathogens enter our body ?

Answer 2

• Cuts in skin
• Through the respiratory system by being inhaled
• Mucosal surfaces e.g Nose, mouth and genitals
• Through digestive system
  -via contaminated food or drink

Question 3

How does stomach acid protect us ?

Answer 3

Question 4

How does skin protect us ?

Answer 4

It acts as a physical barrier to pathogens.
- But if we cut or damage the skin then pathogens on the surface can enter our bloodstream.

Question 5

How does gut and skin flora protect us ?

Answer 5

• Our intestestnes & skin covered in flora.
• They compete with pathogens for space and nutrients
• This limits the number of pathogens living in the gut & skin. Which makes it hard for them to infect the body.

Question 6

How does lysozyme protect us ?

Answer 6

• It kills bacteria by damaging their cell walls causing them to burst open.
• They have a specific shape.
• Mucosal surfaces (e.g mouth and nose) produce secretions (e.g tears, saliva and mucus). These contain lysozyme.

Question 7

What are the types of immune responses ?

Answer 7

• Non-specific (this happens first)
• Specific

Question 8

What is Non-specific immune response

Answer 8

• Immediate response to infection.
• It is not specific to any particular pathogen.
• It involves inflammation the production of interferons and phagocytosis

Question 9

Explain what happens during a Non-specific immune response - Inflammation

Answer 9

• Antigens on the surface of the pathogen are recognised by immune system cells & release molecules that trigger inflammation (e.g histamine).
• These molecules causes vasodilation around the site of infection.
• Which increase blood flow to the site causing redness.
• These molecules also increase the permeability of capillaries.
• Allowing blood plasma to leave the capillary casing swelling.
• The immune system cells can then start to destroy the pathogen.

Question 10

Explain what happens during a Non-specific immune response - Interferons

Answer 10

• Interferons are anti-viral proteins which help to prevent viruses spreading to uninfected cells by :
  1. Inhibit the production of viral proteins to prevent viral replication.
  2. Activate T killer cells to destroy infected cells.
  3. Stimulate inflammation by bringing more immune cells to the site of infection.

Question 11

What is a specific immune response ?

Answer 11

A response that is target to a specific pathogen.
They involve T and B cells(lymphocytes).

Question 12

What is a phagocyte ?

Answer 12

A type of white blood cell that carries out phagocytosis.
- They are the first cell to respond to a pathogen inside the body.

Question 13

Where a phagocytes found ? and give examples of phagocytes,

Answer 13

1. In the blood and tissue.
2. Macrophages, monocytes and neutrophils.

Question 14

Explain the process of phagocytosis.

Answer 14

1. A phagocyte recognises the pathogen as foreign, when receptors on its cell surface bind to antigens on the pathogen’s surface.
2. The phagocyte wraps its cytoplasm around the pathogen, engulfing it.
3. The pathogen is now encosed in a phagosome.
4. Lysosome which contains digestive enzymes (lyso*zymes**) will fuse with the phagosome to form a phagolysosome.
5. Lysozymes digest the pathogen by breaking down its cell wall.
6. The phagocyte then processes the pathogens antigens and presents some of the pathogens antigens on its cell surface. - This is to alert other immune cells of the presence of a foreign antigen. The phagocyte is now referred to as an antigen presenting cell.

Question 15

In phagocytosis, why do phagocytes present some of the pathogens antigens on the surface of their cell.

Answer 15

To alert the immune cells of the presence of a foreign antigen.
- The phagocyte is now referred to as an antigen presenting cell.

Question 16

Explain the process of T cells (like why do they begin to clone themselves) ?

Answer 16

• T cells have receptors on their cell surface.
• Each T cell has a different shaped receptor - so will all bind to different antigens.
• When the receptor on the cell surface of the T cell binds to a complementary antigen displayed by antigen-presenting cells or on a pathogen.
• The T cell will become activated - This is called clonal selection
• Then once activated the T cell will divide by mitosis and produce clones of itself - This is called clonal expansion.

Question 17

Name all the different type of T cells and their functions.

Answer 17

• T helper cells - Release chemicals ( a type of cytokine called interleukins) to activate B cells.
• T killer cells - Bind to the antigens on the surface of pathogens-infected cells to destroy the cell.
• T memory cells - They will divide into T killer & helper cells, if the antigen is detected again at a later date.

Question 18

Explain the process of B cells (like why do they begin to clone themselves) ?

Answer 18

1. They become partially activated when antigens on the pathogen bind to them.
   - This is because they have receptor on their surface.
   - Each B cell has a unique receptor on its surface and will therefore each bind to a different antigen this partially activates the B cell.
   - They then engulf the pathogen and become APC.
   - T helper cells then bind to their antigens now that they have antigens on their surface. This releases cytokines fully activating the B cell causing them to divide by mitosis and differentiate into plasma and memory cells.

Question 19

Name the different B cell and their function.

Answer 19

• Plasma cells : They produce antibodies with a complementary shape to the antigen.
• Memory cells :
  Divide into plasma cells, if the antigen is detected again.
  note: plasma cells are clones of B cells they are literally identical.

Question 20

Give a detailed explanation of the events that take place after a pathogen enters the human body. Draw a diagram to help.

Answer 20

Flashcards:
14
16
18
Or
- Phagocytosis happens (explain phagocytosis)
- At the of phagocytosis there is a macrophage(phagocyte) which becomes an antigen presenting
- The t cells then attach to the apc and then the one that fits the apc specifically it then goes back to the bone marrow and then it divides and differentiates into the t helper cells into killer and helper cells
- Then the t helper cells attaches to the B cell and then it becomes activated and divides into b memory cells and plasma cells. Also when B cells and T cells bind cytokines are released.
- Once the B cells are activated they divide into plasma and b memory cells.
Plasma produces the antibodies.
Note : B cells do not have antibodies on them already they secrete them into the blood.

Question 21

When does the B cell become activated ?

Answer 21

• They become activated when T helper cells release cytokines after binding to acps.
  -They can also become activated when the antigens on the surface of T helper cells bind to their antibodies on their surface

Question 22

Blurt everything you know about Killer T cells

Answer 22

• They work the same way as macrophages (phagocytes).
• Active T killer cells with complementary receptors bind w the antigens on the pathige.
• T killer cells release enzymes
• These create pores in the membrane of the infected cell Ions and water flow into infected cells
• Cell bursts
• Pathogens inside of the infected cell are released
  Outside of cell, labelled by antibodies produced by the B cells
• Macrophages can destroy them
• T killer cells are activated by the cytokines from T helper cells to divide and form active clones (and some memory cells)
• If there were no cytokines, there would not be enough T killer cells to fight the infection

Question 23

Antibody structure

Answer 23

• have a quaternary structure
• made up of four polypeptide chains (two heavy chains and two light chains) held together by disulfide bridges (a a type of bond hold the
  polypeptide chains together)
• They are composed of a variable region (which is different in different antibodies) where the antigen-binding site is located, The antigen-binding site has a complementary shape to the antigen which makes it specific to that particular antigen.
• The hinge region allows flexibility when the
  antibody binds to the antigen.
• The constant regions which is the same for all antibodies it contains another binding site which allows the antibody to bind to immune system cells, such as B cells or phagocytes.

Question 24

What happens after the B cell is activated fully

Answer 24

• It divides into B memory and plasma cells.
• Plasma cells produce antibodies.
• Antibodies will bind to the antigens (as the have a variable region where the antigen binding site is located) which forms an antigen-antibody complex.
• The constant region of the antibody binds to the antibody receptor on the macrophage.
• Macrophage engulfs the antigen-antibody complexes.
• Phagocytosis happens

Question 25

What are the 3 ways that antibodies work to destroy the pathogen

Answer 25

• Agglutinating pathogens
• Neutralising toxins
• Preventing the pathogen binding to human cells

Question 26

Explain agglutination

Answer 26

each antibody has two
binding sites, so an antibody can bind to two pathogens
at the same time — the pathogens become clumped
together. Phagocytes then engulf and digest lots of pathogens at the same time, which makes phagocytosis more efficient.

Question 27

Explain neutralising toxins

Answer 27

• certain pathogens, such as bacteria, make us feel ill by releasing toxins. -antibodies can
  bind to the toxins produced by pathogens which renders them harmless (it neutralises them).
• The antibody-toxin complex can then be destroyed by phagocytes.

Question 28

Explain preventing the pathogen binding to humans

Answer 28

when antibodies bind to the antigens on
pathogens, it prevents the antigen from binding to the receptor molecules on the host cell this means the pathogen can’t
attach to or infect the host cells.

Question 29

What are the two types of way antibodies can be ?

Answer 29

• membrane-bound (e.g. found on the surface of B cells)
• secreted by plasma cells and float freely in the bloodstream.

Question 30

How do membrane bound and secreted antibodies differ ?

Answer 30

• Their heavy chains slightly differ
• The heavy chains of membrane-bound antibodies contain an extra region called the transmembrane region which enables antibodies to attache to the cell membrane of b cells

Question 31

How can a gene can produce two (or more) different proteins ?

Answer 31

Through alternative splicing.

Question 32

Explain the process of alternative splicing.

Answer 32

• Non-coding parts of a gene (the introns) are removed (spliced out) during RNA processing. and the protein-coding regions (the exons) are joined together to form a mature mRNA molecule which can be translated into a protein.
• Alternative splicing happens as certain genes will splice their exons in different combinations they may also remove certain exons, so that different mRNA molecules with a different combination of exons can be produced this means that multiple proteins can be produced from the same gene.
• Which explains why organisms can generate a huge number of proteins from a relatively small number of genes.

Question 33

How is the heavy chain of an antibody coded for ?

Answer 33

Both heavy chain proteins on the membrane-bound and secreted antibody are coded for by a single gene, which is copied
into mRNA (messenger RNA) for protein synthesis.

Question 34

Blurt everything you know about the primary immune response.

Answer 34

• Occurs when you are infected with a pathogen for the first time,
• Both non-specific and specific immune response happen.
• Its slow
• The infected person will experience symptoms while the T and B cells mount an immune response.
• As part of the primary response, both T and B cells produce memory cells.

Question 35

Why is the primary immune response slow ?

Answer 35

• The process is slow because:
  1. The immune system has never encountered the pathogen before, so it takes time to recognize the antigen.
  2. it takes time for the correct B cell to be activated (clonal section) and divide into plasma cells (clonal expansion) in order to produce antibodies with the complementary shape to the antigen.
  3. B cells differentiate into plasma cells that produce antibodies, but it takes time for enough antibodies to be made and reach effective levels to combat the infection.

Question 36

Blurt everything you know about the secondary immune response

Answer 36

• Occurs when your re-infected with the same pathogen in the future
• T and B memory cells will recognise the antigen and start dividing.
• T memory cells will divide into the correct type of T killer cell to kill any cells that are infected with the pathogen.
• B memory cells will divide into plasma cells to produce a large number of antibodies which is complementary to the antigen molecules on the pathogen.
• Is much quicker than the primary response.
• It happens so quickly that the pathogen is suppressed before you are able to experience symptoms - you are immune to the pathogen.