4.6- Immunology And Disease

Question 1

Define the term infection

Answer 1

A transmissible disease often acquired by inhalation, ingestion or physical contact

Question 2

Define the term endemic

Answer 2

Disease occurring frequently, at a predictable rate, in a specific location or population

Question 3

Define the term carrier

Answer 3

Carrier: an infected person or other organism, showing no symptoms but able to infect others

Question 4

Define the term disease reservoir

Answer 4

The long term host of a pathogen, with few or no symptoms, always a potential source of disease outbreak

Question 5

Define the term toxin

Answer 5

A small molecule e.g a peptide made in cells or organisms that causes disease following contact or absorption. Toxins often affect macromolecules e.g enzymes, cell surface receptors

Question 6

Define the term pandemic

Answer 6

An epidemic over a very wide area, crossing international boundaries, affecting a very large number of people

Question 7

Define the term antigen

Answer 7

A molecule that causes the immune system to produce antibodies against it. Antigens include individual molecules and those on virus’s, bacteria, spores or pollen grains. They may be formed inside the body e.g bacterial toxins.

Question 8

Define the term antigenic type

Answer 8

Different individuals of the same pathogenic species with different surface proteins, generating different antibodies.

Question 9

Define the term epidemic

Answer 9

The rapid spread of an infectious disease to a large number of people within a short period of time

Question 10

Define the term vector

Answer 10

A person, animal or microbe that carries and transmits an infectious pathogen into another living organism

Question 11

Define the term antibiotic

Answer 11

A substance produced by a fungus, which diminishes the growth of bacteria

Question 12

Define the term antibiotic resistance

Answer 12

Situation in which a micro organisms that has previously been susceptible to an antibiotic is no longer affected by it

Question 13

Define the term antibody

Answer 13

An immunoglobulin produced by the body’s immune system in responce to antigens

Question 14

Define the term vaccine

Answer 14

A weakened or killed pathogen, toxin or antigen derived from it, which stimulates the immune system to produce an immune response against it without causing infection.

Question 15

Why she we think of ourselves as colonies and not individuals

Answer 15

Because although we have 10 to the power of 13 cells in our bodies, we have at least that number of other individual organisms living in or on the body.

They may be internal (living in our cells, body fluid/gut) or external (on skin and hair)

They include microbes (e.g fungi), protoctista, over 1000 bacterial species in gut flora and larger parasites.

Question 16

Name some examples of parasites in which humans have mutualistic relations with

Answer 16

1) the bacteria E. coil in the large intestine synthesis vitamin K, but in the stomach and small intestine can cause gastro-intestinal disease
2) mites in the hair follicles of eyelashes eat dead cells but can build up and cause inflammation if you don’t remove your mascara.
3) entamoeba is a protoctistan that grazes on dead cells of our gums, if you don’t brush your gums enough when you brush your teeth they will reproduce in large numbers causing gingivitis

Question 17

What happens if we use antibiotics to mutualistic/ beneficial bacteria?

Answer 17

Beneficial bacteria and fungi colonise our skin/gut flora to prevent build up of harmful microbes.
Antibiotics kill such bacteria and :: other organisms e.g yeast increases in number causing disease .
We need to maintain the ecological balance.

Question 18

What organisms suffer from infection and disease?

Answer 18

All groups of organisms because susceptible to pathogens is a property of life as one organism provides habitat to another.

Question 19

Cholera:
What is its cause?
When can it reproduce?

Answer 19

Cholera is caused by her gram negative, comma shaped bacterium vibrio cholerae. It can only reproduce inside a human host.

Question 20

Cholera:
What scale of disease is cholera defined as?
How is it spread?

Answer 20

Cholera is an endemic in parts of the world.
People become infected though contaminated food or water (reservoirs of disease) which contaminate other water supplies and spread the disease.

Question 21

Cholera:

How does it effect a human (biologically)?

Answer 21

• a toxin produced by V. Cholerae in the small intestine affects the chloride channel proteins (CFTR).
• water and ions (Na+, HCO3- etc) are not absorbed into the blood and the patient had severe, watery diarrhoea.
• causes dehydration so blood pressure falls and patient may die.

Question 22

Cholera:

How is it prevented?

Answer 22

1) good hygiene and sanitation (hand washing)
2) better sewage treatment; water purification
3) safe food handling
4) vaccine is available but only given to those with high risk of contraction

Question 23

Cholera:

Describe the treatment

Answer 23

1) water and ions are replaced by giving patient electrolytes (orally or in severe cases intravenously)
2) the bacteria are treated with antibiotics

Question 24

Tuberculosis (TB):
What is its cause?
Why is it named this way?

Answer 24

TB is cause by the bacillus bacterium Mycobacterium tuberculosis.

Named after the tubercles (dead and damaged cells in the lungs) of people who are infected, containing gas filled cavities which are easily seen in xrays

Question 25

Tuberculosis (TB):
How does it spread?
Where does it spread most rapidly?

Answer 25

TB spreads by aerosol transmission (the inhalation if bacteria laden droplets from the coughs and sneezes of infected people).

Spreads most rapidly in crowded condition; densely populated cities etc.

Question 26

Tuberculosis (TB):

How does it effect a person (biologically)?

Answer 26

The bacteria infect the lungs so patients develop chest paid and cough up phlegm which often contains blood.

Bacteria may infect lymph nodes in neck which swell.
People loose appetite and develop fever.

Question 27

Tuberculosis (TB):

How is it treated?

Answer 27

TB is treated with a long course of antibiotics but some strains e.g M. Tuberculosis do show antibiotic resistance.

To prevent TB the BCG vaccine is given to babies and if a skin test proves negative to people up to the age of 16, providing 75% protection, for 15 years. It’s less effective in adults and only given to those at risk.

Question 28

What does a person who has not been exposed to TB carry?

Answer 28

They carry anti-TB antibodies which are detected by a skin test, a negative skin test means they have no antibodies and so they are offered a vaccine.

Question 29

Smallpox:

What is its cause?

Answer 29

Cause by a DNA containing virus, Variola major.

Question 30

Smallpox:

How is it spread?

Answer 30

The virus is inhaled or transmitted in saliva or from other bodies if there is close contact with an infected person.

Question 31

Smallpox:

How does smallpox infect/effect a person biologically?

Answer 31

• it enters small blood vessels in the skin, mouth and throat and is dispersed around the body causing a rash.
• this is followed by the formation of fluid filled blisters which leave scars on survivors.
• some also suffer from blindness and limb deformities.

Question 32

Smallpox:

How are infected people treated?

Answer 32

They are given fluids, drugs to control the fever and pain, and antibiotics to control bacterial infections.
Up to 60% die.

Question 33

Smallpox:

Describe the use of the smallpox vaccine.

Answer 33

-it produces a strong immune response, using live Vaccinia virus (close relative if the smallpox virus) very effecting at preventing the disease.

Before it’s availability, infected people were isolated to prevent the virus spreading.

Question 34

Influenza:
How many subgroups of influenza are there?
Which is best know (the one that our course focus’ on)?

Answer 34

There are 3 subgroups:
‘Flu A’
‘Flu B’
‘Flu C’

Flu A is the best know in which we will focus on.

Question 35

Influenza A:
What does it infect?
Why is this dangerousness

Answer 35

-It infects many species.
-Avian (birds) and swine flu have provided recurrent sources of new influenza virus’s which infect humans.
-when a new strain appears with new proteins on the surface, the human immune system is not able to provide adequate protection.
This lack of immunity causes pandemics to occur.

Question 36

Give an example of a prior (not corona virus) pandemic.

Answer 36

In 1918-1920 Spanish flu infected 500 million people and killed over 50
Million, about 4% if the worlds population at the time.

Question 37

Influenza:

Describe the structure of the influenza virus

Answer 37

It contains RNA in 8 single strands. The virion is surrounded by a phospholipid envelope, derived from the hosts cell membrane. The envelope contains two important proteins which are antigens and are the spikes on the surface of the virus particle.

Question 38

What are the two antigens (the spikes on the surface of the virus particle) called? And what are their roles?

Answer 38

1) Haemagglutinin (H) which has a role in the virus entering a host cell.
2) Neuraminidase (N) which has a role in the virus leaving the host cell.

Question 39

Influenza:

How does influenza affect the body biologically?

Answer 39

The influenza virus attacks mucous membranes, especially in the upper respiratory tract, causing a sore throat cough and fever

Question 40

Influenza:

When does the influenza virus survive best?

Answer 40

When the air is dry and there is low ultra violet light in the environment :: in the winter opposed to summer (giving rise to seasonal flu)!

Question 41

Influenza:

What is the best ways to reduce the risk of infection of influenza

Answer 41

1) regular hand washing
2) using and discarding tissues for coughs and sneezes
3) influenza vaccines can be effective but have variable success because the surface antigens on the virus change and so a new vaccine is needed annually

Question 42

What are the two main origins of the differences between antigenic types?

Answer 42

1) Antigenic drift

2) Antigenic shift

Question 43

Describe antigenic drift

Answer 43

There are no RNA proofreading enzymes, so following each round of replication, every new virion has a new mutation. This produces a gradual change in the surface proteins, which is called antigenic drift. (Explaining why each year a new vaccine is needed.)

Question 44

Describe antigenic shift

Answer 44

Flu A had 16 different types of haemagglutinin of which H1 and H2 are most common in humans. It has 9 different types of neuraminidase of which N1 and N2 are commonest in humans. It one cell is infected by viruses that have different combinations of H and N e.g H1N2 and H2N1, the separate strands of RNA can com combine giving rise to new virus types e.g H2N2.
The new virus formed can cause epidemics.

Question 45

What is an animal reservoir?

Answer 45

An animal e.g chicken or pig which are a source of a new infection produced when an animal virus mutates and becomes able to infect humans.

Question 46

Name some examples of influenza strains

Answer 46

H1N1= Spanish flu (1918) and swine flu (2009)

H5N1= bird flu 2004

Question 47

Malaria:
What is its cause?
How many species of malaria are there and which causes the most deaths?

Answer 47

It is caused by a protoctistan, plasmodium.

There are 5 species which causes malaria but P.falciparum causes the most deaths.

Question 48

Malaria:

How many species of mosquito transmit plasmodium

Answer 48

100 species of anopheles mosquitoes transmit plasmodium, when they pierce skin to take a blood meal.

Question 49

Malaria:

Why are female mosquitos vectors for malaria but males not?

Answer 49

Because females feed on blood whereas males feed on plant nectar.

Question 50

Malaria:

Describe how the severity of malaria changes.

Answer 50

Malaria;

1) is an endemic in some sub-tropical regions
2) can become an epidemic during the wet seaosn
3) can be regarded as a pandemic as it affects millions world wide.

Question 51

Describe the transmission of malaria.

Answer 51

1) when a mosquito takes blood from an infected person it takes in gametocytes (sexually reproducing stage of plasmodium).
2) the gametocytes produce zygotes which develop into an infective stage called sporozoites.
3) sporozoites migrate from the mosquitos but to its salivary glands
4) when the mosquito takes another blood meal plasmodium sporozoites in mosquitos saliva are injected into the human.
5) they travel to the liver and reproduce asexually in the liver cells producing merozoites
6) merozoites are released into the blood and infect red blood cells, where they do more asexual reproduction
7) the red blood cells burst and release more merozoites which infect more red blood cells. This cycle repeated every few days and when the red blood cells burst the fever recurs.
8) some merozoites become gametocytes

Question 52

Why do scientists fear that malaria may spread?

Answer 52

As global temperatures increase malaria is already occurring at higher lattitudes.
They fear that mosquitos may survive in places that were previously unsuitable and that malaria will spread.

Question 53

Malaria;

How do you treat malaria?

Answer 53

It is difficult.
Drugs don’t attack plasmodium when it is inside cells so their effectiveness is limited when plasmodium is in the blood.

Quinine was used in the past but is now not as effective.

Artemisinin is now used in combination with other drugs because it’s unlikely that plasmodium would develop resistance to all the drugs at the same time.

Question 54

Why can’t you treat the P. Falciparum strain of malaria?

Answer 54

Because it mutates frequently and produces many antigenic types, and :: a vaccine has not been possible to produce.

Question 55

Malaria:

Name some preventative measures to reduce the impact of malaria in terms of responding to mosquito behaviour

Answer 55

1) sleep under nets as mosquitos feed between dusk and dawn
2) nets are treated with pyrethroid insecticides to kill mosquitos
3) spray indoor walls with insecticide to kill mosquitos as they rest on walls after feeding
4) drain or cover stagnant water to remove mosquitos access to egg laying sites
5) Pour a film on the water to lower the surface tension and prevent the larvae piercing the surface to obtain oxygen.

Question 56

Malaria:

Name some preventative measures to reduce the impact of malaria in terms of biological control.

Answer 56

1) introduce fish into water so the fish eat the aquatic larvae
2) infect the mosquitos with bacterium Wolbachia as it blocks plasmodium development in the mosquito
3) sterilise Male mosquitos with x-rays so that no offspring is produced after they mate.

Question 57

Why are viruses describe as the ultimate parasite?

Answer 57

Because outside living cells that are inert. They show none of the characteristics of life except when they are inside a host cell and replicated.

Question 58

What happens to viruses in the lyric cycle?

Answer 58

Virus immediately reproduce using the host cells metabolism to copy their own nucleic acid and synthesis new coat protein.

Question 59

How are the virus cells released in the host cell (2 brief methods)

Answer 59

1) lysis of the host cell e.g common cold virus

2) budding where they acquire an envelope from the hosts cell membrane e.g influenza virus

Question 60

What is meant by a lysogenic virus?

Answer 60

A virus which integrates their nucleic acid into the host cell genome remaining there for multiple cell generations with no clinical effect.

They enter the lyric cycle some time later, which is when they produce symptoms e.g herpes, HIV.

Question 61

Describe the viral life cycle

Answer 61

1) Virion attaches to cell
2) Viral nucleic acid injected into cell leaving protein coat outside
3) Nucleic acid and capsid protein are synthesised using the hosts metabolism and they assemble to make mature virus particles.
4) Cell lysis releases the viruses OR new virus particles bud from the cell surface
5) viral nucleic acid integrates into a host cell chromosome (lysogeny)

Question 62

List of all ways in which viruses can be pathogenic

Answer 62

1) Cell lysis
2) Toxins
3) Cell transformation
4) Immune suppression

Question 63

Describe how cell lysis makes a virus pathogenic

Answer 63

When bacteria are infected with bacteriophage the pressure of the new virus particles cause it to burst.

Whereas, in virus-infected animal cells, it is the inflammation caused by T-lymphocytes or antibodies that brings about lysis.

An example is rhinovirus, (common cold strain) which lyses cells in the upper respiratory tract.

Question 64

Describe how viruses having toxins can make them pathogenic

Answer 64

Many viral components and their by-products are toxic.
Examples:
1)Measles virus can cause chromosome fusion
2)Herpes virus can cause cell fusion
3)Viral proteins can inhibit RNA, DNA and protein synthesis

Question 65

Why do antibiotics not affect viruses?

Answer 65

Because viruses don’t have cell walls or metabolic pathways

Question 66

Describe how the virus cell transformation makes a virus pathogenic

Answer 66

Viral DNA can integrate into the host chromosome.
If the DNA inserts into a pro-oncogene or tumour suppressor genes it can become cancerous.

Example= HPV (human papilloma virus) which can cause cervical cancer by inserting into the tumour suppressor gene TP53

Question 67

Describe how the virus immune system makes it pathogenic

Answer 67

1-Suppression of the reactions that cause B and T lymphocytes to mature

2-reduction in antibody formation (e.g HIV destroys a group of T helper cells, so B lymphocytes can no longer make antibodies. People with HIV infection are :: immuno-comprised and highly susceptible to infection.

3-reduction of phagocytise cells engulfing microbes

Question 68

What are antimicrobials? Give 3 examples

Answer 68

Antimicrobials are compounds that inhibit the growth of bacteria. They are:

1) Antiseptics used on living tissue e.g Dettol.
2) Disinfectants used on non-living surfaces e.g bleach
3) Antibiotics