Topic 5: Cells (immune system)

Question 1

What is the human body particularly vulnerable to

Answer 1

• Pathogens
• Bacteria
• Viruses
• Toxins

Pathogens are anything that cause disease

Question 2

What defences does the body have

Answer 2

• Non-specific defences (innate immunity)
• Specific defences (Acquired immunity)

Skin, Mucus,secretions(1st)
Phagocytes(2)
Lymphyctes,memory,Plamsa (3)

Question 3

Define antigens

Answer 3

Antigens are substances or proteins that induces an immune respnse

Question 4

Name the things that lymphocytes will identify

Answer 4

• Pathogens
• Non-self cells (transplants)
• Cancerous cells (abnormal body cells)
• Toxins (from pathogens)

Question 5

Contrast Lymphocytes in feotus and in adult cells

Answer 5

• Fetus
  The lymphocytes are colliding with self cells because they are rarely infected with pathogens. The lymphocytes that have receptors complementary to the self cells will die or be supressed.
• Adult cells
  Lymphocytes are found in the bone marrow, where there is only self cells, so lymphocytes that show an immune response to these self cells will undergo apoptosis, so there are none of these in the blood

Question 6

What do you need to take when you get a transplant

Answer 6

• immunosupressants

Your Lymphocytes will recgonise the cells as non-self

Question 7

If you maintain lymphocytes which attack self cells, what symptoms do you experience?

Answer 7

Autoimmune disease symptoms

* Fatigue
* Skin problems
* Fever

Question 9

What happens when your antigens mutate

Answer 9

If a mutation occurs, inj the gene that codes for the shape pf the antigen (or its tertiary structure) any previous immunity is no longer effective, as your memory cells will only have a memory of the old shape.

Question 10

Are lymphocytes and phagocytes part of the specific, or non-specific response?

Answer 10

• Phagocytes are part of the non-specific response
• Lymphocytes are part of the specific response

Phagocytes attack the same way for any pathogen, therefore non-specific

Question 11

What are Phagocytes?

Answer 11

A type of white blood cell that undergoes Phagocytosis, by engulfing and digesting foreign material.

Question 12

What are Macrophages?

Answer 12

A type of Phagocyte that move around in the bloodstream in search of pathogens

Question 13

Describe Phagocytosis

Answer 13

• Phagocytes are attracted to the chemicals released by foriegn cells, move toward them
• The Phagocytes receptors bind to the antigen of the pathogen, bind if complementary
• This causes the phagocyte to change shape, to engulf the pathogen
• Once engulfed, the pathogen is put in a vesicle called a phagosome
• The phagocytes has the organelle lysosomes in it, which will fuse to the phagosome, releasing lysozymes(lytic enzyme)
• The lysozyme hydrolyses the pathogen, absorbs any soluble products.
• The Phagocyte moves the antigens onto itself, becoming an antigen-presenting cell

Question 14

Where are T-Lymphocytes and B-Lymphocytes matured

Answer 14

T-Lymphocytes in the Thymus
B-Lymphocytes in the Bone marrow

All lymphocytes are made in bone marrow

Question 15

State the situations that produce Antigen-Presenting Cells (ACP)

Answer 15

• Infected Body cells will present viral antigens on their surfaces
• A macrophage that has undergone phagocytosis, will have antigens on its surface
• Cells of a transplanted organ
• Cancer cells ( abnormal shaped self- cell antigens

Question 16

Describe the steps of the cell-mediated response

Answer 16

• You have an ACP
• Helper T-cells (type of T-cells) have receptors which will attatched to the antigens of the ACP if complementary
• Once attatched, the Helper T-cell divide by mitosis, making large number of identical clones which clonal expansion
• The Cloned Helper T-cells differentiate into diff cells by clonal differentiation
• Together this is Clonal selection

ACP (Antigen-presenting cell)

Question 17

What are the possibilites during clonal differentiation

Answer 17

• Stay as Helper T-Cells
• Stimulate Macrophages
• Become Memory cells
• Become Cytotoxic T-Cells

Question 18

What do Cytotoxic T-cells do?

Answer 18

Release the protein perforin, which will make a pore in the cell membrane so that any substance cal leave or enter the cell, which will result in (Apoptosis)

Apoptosis is organised cell death

Question 19

Where can you find antibodies

Answer 19

• Blood
• Tissues
• Tears
• Saliva
• Breast Milk

Question 20

How many polypeptide chains are antibodies made out of

Answer 20

4 polypeptide chains, forming a Yshape.

Question 21

Describe the shape of an antibody

Answer 21

2 Heavy chains, which are longer polypeptides,
2 Lighter chains with shorter polypeptides.
Constant region which is the same in all antibodies.
The variable region which is different in all antibodies.

Question 22

What are the steps of the humoral response?

Answer 22

• Antigen collides with complementary B- cell antibody, the Bcell takes the antigen by endocytosis, and puts it onto its own curface to become an antigen-presenting cell.
• The ACP will collide with a Helper T-cell receptor, to activate the B-cell to undergo clonal expansion and clonal differentiation. (clonal selection)
• They will differentiate into either plamsa cells or memory cells. Plasma cells are responsile for making antibodies. Memory cells are able to rapidly divide into plasma cells upon secondary infection of the same pathogen.

Question 23

What is the role of memory B-cells

Answer 23

They live for decades and are able to divide by mitosis rapidly to make plasma cells with antibodies, upon secondary infection of the same pathogen.

Question 24

Define active immunity

Answer 24

Immuity that is acquired through production of antibodies and memory cells, which results in the pathogen being destroyed before symptoms can occur

Question 25

Primary vs Secondary response

Answer 25

First time ifected = primary response Second time infected = secondary response - quicker response because memory cells will release plasma cells with the antibodies quicker

Question 26

What are the two heavy chains on an antibody joined by

Answer 26

disulfide bonds

Question 27

How do antibodies lead to the destruction of pathogens

Answer 27

* they have a hing region, making antibodies flexible and able to bind to multiple antigens * when the antibody binds to the antigen, it forms an antibody-antigen complex * Because they can bind to multiple antigens, they can clump together called agglutination, making it easier for phagocytes to locate them.

Question 28

What are some other ways that antibodies destroy the antigens

Answer 28

* serve as markers for phagocytes to find * if they bind to free toxic proteins, they can change the shape of the active site, so they can no longer cause disease * by binding to the antigenon bacteria and viruses, they prevent them from attatching to other cells and infecting them.

Question 29

What are monoclonal antibodies

Answer 29

Identical copies of the same antibody

Question 30

Name three uses of monoclonal antibodies

Answer 30

* Pregnancy testing * Medical Diagnosis * Medical treatment

Question 31

How do we use monoclonal antibodies

Answer 31

* Scientists add a fluourescent dye to the constant region of the antibody(to allow it to be visualised) * Then you add the monoclonal antibodies to a group of proteins and it will bind to the correct one

Question 32

Explain direct monoclonal antibody therapy

Answer 32

Monoclonal antibodies with the specific complementarity to the antigens on cancer cells are produced. These will be give to a patient, and they will attatched to the receptors on the cancer cells The antibodies will block the chemical signals that stimulate the uncontrolled cell growth

Question 33

Explain indirect monoclonal antibody therapy

Answer 33

* You produce the antibodies that have complementarity with the antigens on cancerous cells * You then attatch therapeutic drugs to the antibodies, and that will allow for the drugs to be sent directly to the cancerous cells and kill them * This will reduce the harmful side effects of chemotherapy and radiotherapy. * These are often reffered to as bullet drugs

Question 34

How is ELISSA test carried out

Answer 34

1. Antibody specific to the antigen is bound to the bottom of the well, wash out excess 2. Add sample to the well, if antigen present it will bind to the bottom, wash out excess 3. Second-antibody specific to tje antigen is added, this antibody is linked with an enzyme that will cuase a colour change reaction whe you add substrate, wash out excess 4. Add substrate, the colour change that occurs will depend on the concentration of the antigen.

Question 35

How do pregnancy tests work

Answer 35

1. Pregnant woman will produce hCG 2. The hCG will bind to a fluorescent mobile antibody specific to hCG. 3. The hCG with the colour will no bind to an immobilised antibody of hCG, so we can visualise it (first window) 4. There is another antibody that is specific to the first antibody, to ensure that it is present and there is no false positive.

Question 36

What is passive immunity

Answer 36

The antibodies are introduced directly into the body. The pathogen doesnt enter the body, no memory cells ro plasma cells. - Natural Immunity (breastfeeding) - Artificial Immunity (antibody injections) No long term gain | Passive (you didnt make them)

Question 37

What is active immunity

Answer 37

You are infected with the pathogen, therefore you make your own antibodies, memory cells and plasma cells. - Natural immunity ( when infected) - Artificial immunity (through vaccination) | Long term advantage

Question 38

Explain vaccination

Answer 38

* Weakened / dead form of the pathogen * Exposure to the antigens triggers B-lymhpcytes to undergo clonal selection. * The B-cell will then undergo mitosis to make large number of cells. * This is a primary response

Question 39

Explain antigen variability

Answer 39

Antigens are protiens, which will be coded for by DNA, so if there is a mutation in the gene that codes for the DNA, the antigen shape will change, resulting in all previous immunity to be lost, because all your memory B-cells will only have immunity to the previous shape. This is why vaccinations need to be topped up.

Question 40

Name the features of HIV

Answer 40

* Attatchement proteins (to enable binding to Helper T-Cells) * Lipid envelope (made from same as hosts * Protien Capsid(outer protein coat) * Viral RNA(core: genetic material (RNA) and enzyme reverse transcriptase, which is needed for viral replication

Question 41

How does HIV replicate

Answer 41

1. HIV travels in the blood, until it attaches with surface protien on a helper-t cell, using its attatchment proteins 2. The HIV capsule fuses with Helper-Tcell membrane, enables the RNA and enzyme reverse transcriptase to enter host cell. 3. Reverse Transcriptase copies viral RNA into a copy of DNA. The DNA copy moves into the host cells nucleus 4. The viral DNA integrates into the host cells DNA, and is transcribed into more viral mRNA. The mRNA will use Helper-Tcell to make viral proteins . This destroys the Helper T-cells 5. New viral proteins moe back towards the mebrane , and pinch off to become a new HIV particle.

Question 42

What is AIDS

Answer 42

AIDS, is when your HIV replicating viruses intefere with the normal functioning of the immune system. Eventually, to many helper Tcells will be destroyed therefore your immune system is compromised and you are more susceptible to infections and cancer.