Chapter 2 - Immunity Flashcards

Question

What are foreign (non-self) cells?

Answer 1

Cells not recognised by the body

Answer 2

They will produce and immune response.

Answer 3

Specific molecules, or clusters of molecules, that form part of the cell surface membrane of the foreign cell. These molecules are often protein, but can be other substances, for example, polysaccharides, glycoprotein and glycolipid, and are collectively referred to as antigens.

Answer 4

Different antigens

Answer 5

The immune response is specific to these antigens.

Answer 6

Textbook page 22

Answer 7

* This specific response is due to the lymphocyte having a receptor on its cell surface membrane that is complementary in shape to the antigen. * Antigen and lymphocyte fit together like substrate and enzyme in the lock and key model of enzyme action.

Answer 8

A chemical capable of producing a specific immune response.

Answer 9

* There are many million different types of lymphocytes, each having receptors with a complementary shape to a potential antigen. * In the foetus, these lymphocytes frequently make contact with other foetal (self) cells. * Lymphocytes that are complementary in shape with foetal cells are 'switched off' so by the time the baby is born the functional lymphocytes that remain are those that are not complementary to self cells.

Answer 10

There are many million functional lymphocytes within the body, but there are only a few of each type that are specific to the invading pathogens antigens.

Answer 11

B-lymphocytes (B-cells) | T-lymphocytes (T-cells)

Answer 12

Formed from stem cells in the bone marrow

Answer 13

Formed from stem cells in the bone marrow

Answer 14

Mature in bone marrow

Answer 15

Mature in thymus gland | lymph gland in the neck

Answer 16

Antibody-mediated (humoral) immunity

Answer 17

Cell-mediated immunity

Answer 18

* Produce antibodies which respond to antigens found in body fluids (for example, blood and tissue fluid). * Respond usually to bacterial or viral infection.

Answer 19

* Respond to antigens attached to body cells. | * Respond usually to body cells affected by viral infection.

Answer 20

* An antigen will come into contact with its complementary lymphocyte - a process that may take some time due to the small numbers involved. * When this happens the lymphocytes become sensitised or activated.

Answer 21

Similarity • In both B and T-cells, sensitised lymphocytes are cloned (involving division by mitosis). Difference • In B-lymphocytes, certain genes are activated to set in motion a process that eventually leads to the production of antibodies. • Whereas in T-lymphocytes, a number of types of T-cell are produced, each type having different roles in the battle against infection.

Answer 22

The production of T-cells is stimulated by the body's own cells that have been changed due to the presence of non-self material within them.

Answer 23

Body cells that have been changed due to the presence of non-self material within them.

Answer 24

Antigen-presenting cells

Answer 25

1. Macrophages (phagocytes) that have engulfed and broken down a pathogen and 'present' some of the pathogen's antigens on their own cell surface membrane. 2. Any type of body cell that has been invaded by a virus - again some of the viral antigens are presented on the cell surface membrane of the body cell (remember, viruses cannot live on their own, they must live inside other cells). 3. Cancer (tumour) cells, as many cancer cells present abnormal antigens on their cell surface membranes.

Answer 26

Textbook page 24

Answer 27

1. Killer (cytotoxic) T-cells 2. Helper T-cells 3. Suppressor T-cells (also known as regulatory T-cells) 4. Memory T-cells

Answer 28

• Killer (cytotoxic) T-cells destroy infected cells by attaching to the antigens on the cell surface membrane of the infected or abnormal cell and destroying it by direct enzyme action.

Answer 29

* These cells stimulate other cells involved in the immune response, for example, they stimulate B-cells to divide (and produce the plasma cells that produce antibodies) and promote the process of phagocytosis through their effect on phagocytes. * Phagocytosis is a slow process without the activating role of the helper T-cells. * They also attach special chemicals (opsonins) to the pathogens that mark them out for the attention of phagocytes. * Helper T-cells also secrete the protein interferon that helps limit the ability of viruses to replicate.

Answer 30

* These cells 'suppress' the immune response of other immune cells when required. * Suppressor T-cells switch off the immune response after invading microbes and infected cells have been destroyed. * They are also important in preventing autoimmune responses, the situation where the immune system attacks 'self' cells in the body. Note: Suppressor T-cells deactivate the immune response of both B and T-cells.

Answer 31

* These cells circulate in body fluids and can respond rapidly to future infection by the same pathogen (presenting the same antigen(s)). * If a subsequent infection occurs, as the memory cells are already sensitised, they can very rapidly produce a large clone of T-lymphocytes.

Answer 32

It is thought that the onset of Type 1 diabetes, an autoimmune condition, is linked to reduced numbers of a type of suppressor T-cell, resulting in a cell-mediated attack on the insulin-producing cells in the pancreas.

Answer 33

Microorganisms (usually bacteria or viruses) that are found in the body fluids (for example, blood and tissue fluid), rather than in body cells.

Answer 34

Through the production and action of antibodies

Answer 35

Antibodies can be defined as globular proteins which are complementary to specific antigens and which can react with the antigens (microbes) leading to their destruction.

Answer 36

Textbook page 25

Answer 37

* Pathogen is present in the body fluids. * B-lymphocyte that has a receptor with the exact complementary fit to the bacterial antigen is sensitised * A sensitised (activated) B-lymphocyte divides rapidly by mitosis to form a clone. The cloned cells develop into plasma cells and memory cells.

Answer 38

Specific B-lymphocytes

Answer 39

Have receptors that match the pathogen's antigens.

Answer 40

A particular type (or types) of B-lymphocyte becomes cloned.

Answer 41

Different types of cell, in the case of B-cells, plasma cells and memory cells.

Answer 42

Plasma cells

Answer 43

Plasma cells are short lived (a few days) but each produces very large numbers (many millions) of antibodies.

Answer 44

The antibodies neutralise the pathogens as a consequence of antigen-antibody reactions.

Answer 45

As a consequence of a specific antibody-mediated immune response

Answer 46

Complementary in shape.

Answer 47

* The antibodies latch on to the bacterial antigens clumping the bacteria together. * Typically, the build up of antibodies in the body fluids will enable a sufficient number to be present to immobilise the bacteria causing their agglutination or clumping as an antigen-antibody complex.

Answer 48

In due course the antigen-antibody complex (clump of bacteria and antibodies) is engulfed by polymorphs and other phagocytes.

Answer 49

Textbook page 26

Answer 50

1. Agglutination. 2. Destruction of the invading cells directly via antigen-antibody reactions. 3. Antibodies can also act as opsonins by attaching to pathogens and marking them for phagocytosis.

Answer 51

Antibodies are globular proteins that are complementary in shape to a specific antigen.

Answer 52

As small changes in the sequence of amino acids in the primary structure can produce the millions of different three-dimensional shapes required to be complementary in shape to the range of antigens that exist.

Answer 53

Exactly the same shape (and both are complementary in shape to the antigens on the invading pathogen).

Answer 54

For many years (sometimes for life) in the body fluids.

Answer 55

* Memory cells produced by B-cells can live for many years (sometimes for life) in the body fluids. * These cells remain inactive unless stimulated by the presence of the same antigen (pathogen) again. * If this happens, the memory cells divide rapidly (they are already sensitised) and produce vast numbers of plasma cells, as there are more memory cells than there were 'correct' B-cells at the start of the primary response. * The plasma cells produce the antibodies necessary to destroy the pathogen while the memory cells provide a guarantee of further long term protection.

Answer 56

The initial response of the body to the antigen when meeting it for the first time.

Answer 57

The secondary immune response

Answer 58

The secondary response of the body to the antigen when meeting it for the second time, involving memory cells.

Answer 59

Many different types of antigen

Answer 60

Produce an immune response with a different type of B-lymphocyte.

Answer 61

For any one type of pathogen there may be many different antigen-antibody reactions taking place at the same time.

Answer 62

No one individual is immune to all potential pathogens and diseases. However, individuals can be immune to (protected against) specific diseases.

Answer 63

Active | Passive

Answer 64

Passive immunity is when the individual receives antibodies from another source (ie from outside the body).

Answer 65

Active immunity is when the individual achieves immunity through the production of antibodies by his/her own body.

Answer 66

1. Antibodies passing from mother to baby across the placenta and in the mother's milk (colostrum). - The passive immunity that this produces is crucial in the very early stages of life, a time when the baby's immune system is still developing. 2. Antibodies made in another individual, which are harvested and injected into another person as serum. - The antibodies can be obtained from individuals recovering from illness (they will have high levels of the required antibody in their blood). - An older method of obtaining antibodies involved immunising animals, for example horses, with attenuated pathogens or their inactivated toxins. - This causes the animal to produce the antibodies required and serum from the animals was given to individuals requiring rapid immunity.

Answer 67

Blood plasma with all blood clotting substances removed.

Answer 68

As this is during a time when the baby's immune system is still developing.

Answer 69

1. From individuals recovering from illness (they will have high levels of the required antibody in their blood). 2. An older method of obtaining antibodies involves immunising animals (for example, horses) with attenuated pathogens or their inactivated toxins. This caused the animal to produce the antibodies required and serum from the animals was given to individuals requiring rapid immunity. 3. Monoclonal antibody production.

Answer 70

Monoclonal antibody production

Answer 71

Monoclonal antibody production

Answer 72

1. Specific antigen (not a microbe) is injected into a mouse. 2. Sensitised and cloned B-lymphocytes are removed from the mouse that has been infected with the particular antigen. 3. The short lived mouse B-lymphocytes are hybridised with laboratory cultured tumour (cancer) cells (which are rapidly dividing and long lived ie immortal). 4. The two cell types are fused together, combining the properties of each to produce long lived hybridoma (hybrid) cells that are cultured in optimum conditions (ie in a fermenter over a long period of time) to maximise monoclonal antibody production.

Answer 73

Textbook page 27

Answer 74

Monoclonal antibodies have many advantages compared to obtaining antibodies from horses or other large mammals: * Can be produced in large quantities in the laboratory. * Can produce a single type of antibody (antibodies obtained from horses usually come as a range of types, together with other chemicals that can potentially cause allergies).

Answer 75

* Passive immunity provides rapid immunity as the processes of B-lymphocyte sensitisation and plasma cell production do not need to take place first. * It is especially effective if someone becomes infected with a particularly harmful pathogen when it is probable that they have no defence against it (for example, a 'new' disease encountered in a foreign country or when suffering from a snake bite).

Answer 76

Passive immunity is only temporary, as in time the antibodies are broken down and the individual's immune system is not programmed to make more.

Answer 77

Textbook page 28

Answer 78

From having had the disease, or via vaccinations.

Answer 79

* The individual becomes ill but recovers as a consequence of the primary response to the infection. * The primary immune response is slow to develop and the individual usual suffers the disease symptoms for a period of time (it may take 4-5 days before antibody levels reach a high enough level to be effective in a primary response, due to the time involved in activating the specific B-lymphocytes and producing plasma cells) but once in place it is long lasting. * Should a subsequent infection occur, involving the same pathogen, the secondary response is so rapid and strong that the immune system may destroy the pathogen(s) so quickly that the individuals may not even be aware that they were infected.

Answer 80

There are many more memory cells than there were specific B-lymphocyte cells at the start of the primary response (strength) and the memory cells are already sensitised (speed).

Answer 81

Although some antibodies can last in the blood for a considerable length of time, the fact that active immunity is long lasting is primarily due to the presence of memory cells and their ability to respond quickly and effectively if a subsequent infection occurs.

Answer 82

Active immunity

Answer 83

Many diseases

Answer 84

Measles and mumps

Answer 85

Early in childhood.

Answer 86

To stop individuals being affected by potentially common and harmful infectious diseases.

Answer 87

The body has been infected by a particular pathogen

Answer 88

The primary immune response is triggered and the immune system is equipped to produce a secondary response if required.

Answer 89

The speed and strength of the secondary response renders the individual immune.

Answer 90

Vaccinations normally contain one of the following: 1. Killed or weakened (attenuated) pathogens - These pathogens contain the antigens required to produce an immune response but they will not cause the disease itself (however, mild symptoms may sometimes appear). 2. Modified toxins produced by the pathogen - With some pathogens it is their toxins that can produce the immune response. - The toxins must be modified and made harmless but not changed so much they do not produce an immune response. 3. Isolated antigens separated from the pathogen itself - For some pathogens the antigens can be made by genetic engineering.

Answer 91

Subsequent booster injections

Answer 92

These produce a secondary immune response, similar to the response produced when catching a particular disease for a second time.

Answer 93

Textbook page 29

Answer 94

Active immunity

Answer 95

There are fewer sick people and the lives of many people are extended, often considerably.

Answer 96

Largely due to the increasing availability of vaccination programmes.

Answer 97

1. Fewer people are ill. 2. Less care is needed to tend the ill. 3. Healthy children tend, on average, to do better at school.

Answer 98

The overall benefit to a nation's economy is much greater.

Answer 99

1. There are lower treatment costs to treat those who are ill. 2. Employees do not have to take time off work, therefore productivity increases. 3. Carers, for example parents, do not have to take time off work to care for the sick.

Answer 100

Billions of pounds annually

Answer 101

Reducing illness from infectious disease.

Answer 102

Herd immunity

Answer 103

If a high enough proportion of the population is vaccinated, those who are not vaccinated are less likely to catch a particular infectious disease (as they are less likely to come into contact with someone who is infectious).

Answer 104

- Herd immunity is very important in protecting those who cannot get vaccinated, for example newborns (first NHS immunisation is currently at six weeks) and the very ill. - Of course, it also helps protect the small numbers who, against medical advice, choose not to get vaccinated.

Answer 105

Active | Passive

Answer 106

Natural | Acquired (artificial)

Answer 107

Natural (innate) | Acquired (artificial)

Answer 108

Immunity developed through having had the disease

Answer 109

Acquired via vaccination

Answer 110

Immunity from mother via placenta or milk (colostrum)

Answer 111

Immunity via an injection of antibodies

Answer 112

Textbook page 30

Answer 113

When it detects the presence of any non-self antigens.

Answer 114

Transplanted organs (such as kidneys) or tissue (such as skin grafts) will also produce an immune response.

Answer 115

As the transplanted organ/tissue will contain non-self antigens if they come from someone else.

Answer 116

- The tissue is transplanted within the same person (as can happen with skin grafts) OR - If tissues/organs are transplanted between identical twins (identical twins are genetically identical and therefore they have identical antigens).

Answer 117

Do not take place between identical twins

Answer 118

A protein called perforin

Answer 119

The risk of transplant rejection exists.

Answer 120

Transplant rejection

Answer 121

1. T-lymphocytes are stimulated (sensitised) by the non-self antigens present in the transplanted tissue. 2. These T-cells are cloned by mitosis to produce killer T-cells (and the range of other T-cells associated with cell-mediated immunity). 3. The killer T-cells destroy the transplanted cells.

Answer 122

B-lymphocytes and antibodies

Answer 123

If the blood of a donor and a recipient is different, this can produce an immune response involving antibodies.

Answer 124

As normally tissue matching is accurate so rejection by B-lymphocytes in this situation is unlikely to occur.

Answer 125

As organ transplants may be a last resort in saving a life or even in providing a better quality of life for a patient.

Answer 126

Devising strategies for reducing transplant rejection.

Answer 127

1. Tissue typing 2. Immunosuppression techniques 3. X-rays

Answer 128

- This is the term that describes the process of matching the donor and recipient cell surface markers (antigens) so that there is as good a match as possible, ie there is as small a difference as possible between the self and non-self antigens. - Generally, the best tissue matching will take place between close relatives. - The best possible transplant will be between identical twins, who will have identical antigens therefore the transplant is much less likely to be rejected.

Answer 129

- Immunosuppression techniques such as the use of drugs to inhibit DNA replication and therefore the cloning of lymphocytes (and the production of killer T-cells) will slow down or stop rejection processes. - For many types of transplant, the immunosuppression drugs have to be taken for a very long time (for the life of the transplant and therefore often for life).

Answer 130

- Can be used to inhibit the production of lymphocytes through the irradiation of bone marrow or lymph tissue. - Unpleasant side effects can result and the use of X-rays is usually a backup to immunosuppressant drugs rather than a first course of action.

Answer 131

Immunosuppression (whether by drugs or X-rays) will compromise the recipient's immune system.

Answer 132

This makes the individual susceptible to infection.

Answer 133

As immunosuppression depresses the immune system in general (not just its response to the antigens involved in the transplanted tissue).

Answer 134

* Anti-viral drugs * Anti-bacterial mouth rinses * Anti-T-cell monoclonal antibodies to help target and reduce the effect of the T-cells involved in rejection.

Answer 135

A delicate balance between reducing the risks of rejection and restricting the side effects that are linked to the use of immunosuppressant technologies.

Answer 136

Textbook page 31

Answer 137

Red blood cells also have antigens (markers) on their cell surface membrane just like other body cells.

Answer 138

The blood of any one individual will not have antibodies that correspond to the antigens on his/her red blood cells as this would trigger an immune reaction.

Answer 139

Switched off during very early development

Answer 140

The ABO system

Answer 141

Four A B AB O

Answer 142

Belongs to one of these groups.

Answer 143

Polymorphism

Answer 144

A situation where there are several distinct categories or forms.

Answer 145

Following surgery Following an accident When treating a specific illness

Answer 146

The transfusion is compatible.

Answer 147

Because the recipient has no anti-a antibodies that correspond to the antigens on the donor's red blood cells.

Answer 148

* Because the recipient has anti-a antibodies in his/her plasma. * The presence of both antigen A and anti-a antibodies causes an antigen-antibody reaction. * The anti-a antibodies cause the blood, containing red blood cells with antigen A, to agglutinate or clump. * This agglutination could block capillary networks and lead to organ failure and death.

Answer 149

Anti-a antibodies

Answer 150

As they had no A antigens in early development; therefore, A antigens were not identified as self antigens and the lymphocytes responsible for producing antibody-a were not 'switched off'.

Answer 151

Textbook page 32

Answer 152

Both antigens A and antigens B

Answer 153

Neither antigens A nor antigens B

Answer 154

Anti-b antibodies

Answer 155

Anti-a antibodies

Answer 156

Neither anti-a nor anti-b antibodies

Answer 157

Both anti-a and anti-b antibodies

Answer 158

Which blood can be transfused into which other type(s).

Answer 159

The donated blood type does not lead to an antigen-antibody reaction and subsequent agglutination.

Answer 160

Textbook page 32 Blood group of donor/ Blood group of recipient

Answer 161

Transfused into any of the four blood groups.

Answer 162

As blood of group O does not have either A or B antigens.

Answer 163

The universal donor

Answer 164

Blood group O is referred to as the universal donor.

Answer 165

Receive blood from any group.

Answer 166

As they lack both anti-a and anti-b antibodies

Answer 167

The universal recipient

Answer 168

The universal recipient

Answer 169

Donated blood is mainly red blood cells and the amount of donated plasma is insignificant.

Answer 170

None, or a very insignificant number of, anti-b antibodies in blood group A will be transfused into the recipient with blood group AB.

Answer 171

* It is thought that the different antigens (groups) evolved as a consequence of mutations. * Currently, none of the blood groups appears to give individuals a selective advantage (ie the mutations are neutral). * However, it is possible that in our evolutionary past some of the mutations gave selective advantage against specific diseases - this would explain why the different groups have persisted through time.

Answer 172

A number of many blood group systems in humans.

Answer 173

The most important in clinical practice.

Answer 174

The ABO system

Answer 175

The rhesus system

Answer 176

The presence or absence of an antigen (the rhesus antigen or antigen D) on the cell surface membranes of the red blood cells.

Answer 177

Around 85%

Answer 178

Rhesus positive

Answer 179

Textbook page 33

Answer 180

Do not have the antigen.

Answer 181

Do not occur naturally in the plasma.

Answer 182

As relevant B-lymphocytes are 'switched off' when the rhesus positive marker is recognised as self during development.

Answer 183

* An individual who is rhesus positive will not produce anti-D antibodies (relevant B-lymphocytes are 'switched off' when the rhesus positive marker is recognised as self during development). * Rhesus negative individuals do not normally have the antibodies either, but can produce anti-D antibodies if their blood becomes contaminated with blood containing antigen D.

Answer 184

1. Blood transfusion between a rhesus positive donor and a rhesus negative recipient. In reality, this is unlikely to occur with modern blood matching techniques. 2. When a rhesus negative mother has a rhesus positive baby.

Answer 185

1. During birth (or late in pregnancy) some foetal red blood cells (rhesus positive so contain antigen D) leak into the mother's circulation. 2. This causes the rhesus negative mother's immune system to produce anti-D antibodies. By the time the antibodies are produced in significant numbers by the mother, the baby will have been born therefore there is no threat to the developing foetus. 3. However, during subsequent pregnancies, if the foetus is rhesus positive, the relevant B-lymphocytes in the mother are already sensitised and large numbers of anti-D antibodies can be produced immediately if any foetal blood cells enter the maternal circulation. The anti-D antibodies can cross the placenta and cause agglutination of foetal red blood cells, a condition known as haemolytic disease of the newborn.

Answer 186

Agglutination of foetal red blood cells can lead to death, or serious illness.

Answer 187

* As rhesus negative mother's are treated during pregnancy (around 30 weeks) by being given an injection of anti-D antibodies. * These attach to any antigen D-containing foetal red blood cell fragments that may pass across the placenta and enter the mother's circulation before the mother's B-lymphocytes are stimulated to produce anti-D antibodies. * Following birth, if the baby proves to be rhesus positive, another injection of anti-D antibodies is given with 72 hours. * However, if medical screening and intervention is bypassed and the condition does occur, the baby can be treated by blood transfusion.

Answer 188

By blood transfusion

Answer 189

Drugs that are developed to kill bacteria.

Answer 190

In different ways

Answer 191

* Disrupt cell wall formation by inhibiting an enzyme involved in the process. The bacteria are killed as the cell bursts, as it cannot resist osmotic pressure due to a weakened cell wall. Penicillin works in this way. * Inhibit metabolic processes including protein synthesis, for example, erythromycin destroys the ribosomes in prokaryotic cells.

Answer 192

The fact that erythromycin does not affect the larger ribosomes (80S) in eukaryotic cells means it can disrupt protein synthesis in bacteria (70S ribosomes) and not damage the ribosomes in patients taking this antibiotic.

Answer 193

More and more species of bacteria are becoming antibiotic resistant.

Answer 194

One, or more, antibiotics no longer have an effect on them.

Answer 195

Antibiotic resistant

Answer 196

Metabolic changes that result in antibiotics no longer being effective

Answer 197

By binary fission (asexually), one resistant bacterium can very rapidly result in a large population of antibiotic resistant bacteria.

Answer 198

Textbook page 34

Answer 199

Penicillin-resistant bacteria have evolved a number of methods of resisting the effects of penicillin.

Answer 200

* Producing penicillinase to break penicillin down. * Exporting the active ingredient in penicillin out of the cell before it can work. * Alternative metabolic pathways in cell wall formation that render the penicillin ineffective.

Answer 201

Resistant to a number of types of antibiotics

Answer 202

That some strains could become resistant to all antibiotics

Answer 203

A so-called 'antibiotic winter'.

Answer 204

1. A more rigorous hygiene culture in hospitals. 2. More effective isolation of MRSA patients. 3. A more judicious approach to antibiotic use. 4. New targeted drug treatments.

Answer 205

The problem of antibiotic resistance is decreasing!

Answer 206

New sources of antibiotics are found.

Answer 207

As many bacteria are antibiotic resistant to the current generation of antibiotics.

Answer 208

Bacteria that are resistant to the current generation of antibiotics will not be resistant to 'new generation' antibiotics that work in different ways.

Answer 209

Similar to the benefits of having vaccination programmes with very high rates of uptake, ie more effective treatment, less treatment costs and less time off work.

Answer 210

Finding new sources of antibiotics in natural environments

Answer 211

Some types of microbe naturally produce antimicrobial substances as a defence mechanism within the soil against competing microbes.

Answer 212

The antibiotic properties of some bacteria that are naturally found in the human nasal cavity.

Answer 213

1. How easily it is spread from person to person. 2. How likely someone will fall ill to the disease once infected. 3. Whether there is a vaccination for that disease and the percentage uptake of that vaccination. 4. Bacterial resistance to antibiotics is another factor if the disease in question is caused by a bacterium.

Answer 214

A disease that spreads rapidly through a small region (usually within one country) and affects a higher proportion of the population than normal.

Answer 215

A disease that affects many thousands of people or several countries at the same time.

Answer 216

Although scientists are very worried that antibiotic resistance in bacteria could lead to the rapid spread of previously controlled bacterial infections, most major epidemics and pandemics are caused by viruses.

Answer 217

1. Viruses have very small genomes that are prone to mutation. 2. Many disease-causing viruses are retroviruses with RNA in the genome. These viruses are much less stable than those with the genome as DNA. 3. Antibiotics are not effective against viruses.

Answer 218

``` Influenza SARS rabies Hendra Ebola AIDS ```

Answer 219

HIV infection)

Answer 220

30 million plus deaths over the last few decades.

Answer 221

The 'Spanish' flu virus killed between 30-50 million people in a worldwide pandemic in 1918-1919.

Answer 222

HIV, a retrovirus that converts its RNA to DNA in host cells.

Answer 223

Long term damage to their immune systems with the result that they eventually succumb to one or more of the diseases associated with AIDS.

Answer 224

The disease-causing virus

Answer 225

HIV positive (ie they produce antibodies to the antigen(s) of this virus).

Answer 226

The syndrome of diseases associated with long term infection with HIV; diseases that are a consequence of a much weakened immune system.

Answer 227

* It is thought that the HIV virus mutated from a similar virus (SIV) that causes the same type of immunodeficiency in chimpanzees that HIV does in humans. * The virus 'transferred' to human(s) in the early 1900s in central Africa, possibly through a human being bitten by a chimp or through eating or handling chimp meat.

Answer 228

* Once HIV had evolved in humans, the disease AIDS was restricted to isolated pockets in central Africa for decades and only came to widespread public attention in western countries in the 1980s. * Major reasons for AIDS 'exploding' in western populations at that time included the advent of globalisation, the development of a more casual approach to sex in many societies and the increased use of air travel. * Each of these factors contributed to more opportunity for infection by HIV carriers in previously HIV-free societies.

Answer 229

1. The advent of globalisation. 2. The development of a more casual approach to sex in many societies. 3. Increased use of air travel.

Answer 230

To more opportunity for infection by HIV carriers in previously HIV-free societies.

Answer 231

* (Until recently) HIV meets many of the criteria associated with disease-causing microbes that can potentially cause epidemics or pandemics. * It is an unstable retrovirus that has high rates of mutation. * It is not controlled by antibiotics. * It cannot be vaccinated against * (Until recently) there are very few drugs that are effective in its control.

Answer 232

New antiretroviral drug treatments have significantly reduced death rates from HIV, greatly extending the life expectancy of patients with the condition.

Answer 233

A similar virus (SIV) in chimpanzees.

Answer 234

Crossing over into humans.

Answer 235

Co-existed with its primate hosts for a very long time.

Answer 236

Reservoirs for that virus.

Answer 237

* Animal species that harbour viruses that subsequently cause disease in humans are described as reservoirs for that virus. * Reservoir species often suffer little harm from the viruses and they are not really vectors as such, as they are not adapted to transfer the pathogen to another species; if a transfer does occur, it is usually a chance event.

Answer 238

The reservoir origins of the viruses responsible for causing these conditions.

Answer 239

Transferring from other animal species to humans and then causing epidemics and pandemics.

Answer 240

A range of bat species have had a very significant role in this inter-species spread.

Answer 241

Reservoirs for the viruses that cause Marburg, SARS and Nipah, and are an initial reservoir for rabies before its transfer into dogs (and then into humans).

Answer 242

1. They are mammals and have a very similar physiology to humans. 2. They are social animals and are in very close contact with large numbers of other bats, thereby ensuring that a high proportion of the bat population are carriers, thus increasing the possibility of cross-infection. 3. They fly large ranges and therefore are potentially in contact with other organisms (humans) considerable distances away from their base.

Answer 243

The continual encroachment of man into habitats frequented by bats as a consequence of urbanisation and the clearing of woodland for housing and agriculture.

Answer 244

The 'flying foxes' or 'fruit' bags found in tropical and sub-tropical areas; not the bats found in the British Isles.

Answer 245

Antimicrobials are developed.

Answer 246

Antimicrobial drugs are drugs that are effective against a broader range of microbes than antibiotics, or are effective against those pathogens that antibiotics cannot combat, for example, viruses.

Answer 247

Significant progress in the earlier, and more accurate, diagnosis of infection.

Answer 248

More effective treatment at an earlier stage of disease progression.

Answer 249

ELISA techniques and the detection of cytokines as biomarkers.

Answer 250

Enzyme-linked immunosorbent assay

Answer 251

This is a laboratory technique that uses antibodies, enzymes and other molecules as biomarkers to detect the presence of particular molecules in the body.

Answer 252

ELISA assays can test for a small, or large, number of potential antigens or biomarkers at the same time, thus screening for a large number of possible conditions.

Answer 253

* Typically, body fluids from a patient are added to a number of wells on a plate (a sophisticated spotting tray) and a range of antibodies are added to these wells. * Reaction between antibody and antigen triggers an enzyme linked to the antibody into causing a colour change thus identifying the antigens or other molecules present.

Answer 254

* Pathogens in the body * Cancer cell markers * Cardiac disease markers * Pregnancy (in home pregnancy kits)

Answer 255

They have the advantage of enabling early, rapid screening and can provide a wide range of diagnostic feedback from the one test.

Answer 256

* Following the implantation of an egg in the uterine wall, increased levels of the hormone chorionic gonadotropin (hCG) can be detected in the blood or urine. * In a pregnancy test, hCG antigens are detected by complementary hCG (monoclonal) antibodies immobilised on the ELISA test plate. * The formation of this antigen-antibody complex results in a linked enzyme reacting to produce the characteristic colour change associated with pregnancy test kits.

Answer 257

* An ELISA plate impregnated with the viral antigens is coated with blood serum from the patient. * If the patient's blood contains complementary antibodies (evidence of infection), then the antigen-antibody complex triggers an enzyme reaction that leads to a colour change.

Answer 258

* The antibody-antigen complex normally stimulates the enzyme reaction, it is not the substrate as such. * The substrate for the enzyme is normally added as part of the process.

Answer 259

* Chemicals released by T-helper and other cells as part of the immune response during infection. * They are small proteins that help coordinate the immune response. * They can be found in the blood and are used as biomarkers to identify a number of conditions including TB and rheumatoid arthritis.

Answer 260

Prevent contamination when working with microorganisms.

Answer 261

Aseptic technique

Answer 262

Preventing contamination of both the microbe culture and contamination of the individuals working with the microbes

Answer 263

Solid agar or liquid broth

Answer 264

Transferring microorganisms to Petri dishes or other containers for investigation.

Answer 265

Metal inoculating or disposable plastic loops can be used. 1. If using a metal inoculating loop it is necessary to 'flame' the loop in the hottest part of a Bunsen flame until it becomes red-hot. - After sterilising the metal loop it is necessary to air-cool the loop as when red-hot it would kill any microorganisms it comes into contact with. - After transfer of microorganisms, it is necessary to re-sterilise the loop. - However, for safety reasons it is important not to create a microorganism-rich aerosol when doing this. - Once used, disposable plastic loops should be discarded into a solution of disinfectant. 2. When transferring microorganisms from a culture bottle to a Petri dish (or a fresh culture bottle), the lid of the bottle should be held in the same hand that holds the culture bottle and not allowed to touch the bench, with the other hand holding the inoculating loop. - Immediately after opening the culture bottle, it's neck should be quickly passed through the Bunsen flame to sterilise the lid region; this should be repeated immediately before replacing the lid on the culture bottle. 3. When transferring the microorganisms to a Petri dish, the lid of the dish should be only raised enough to allow the microorganisms to be added to the agar. * Petri dishes should be labelled on the outside of the base (and not the lid). * They should be incubated upside down in an incubator at an appropriate temperature for the microorganism concerned.

Answer 266

• Alternatively, a spread plate method can be used, when cells in suspension are used in inoculation. - In this case an L-shaped spreader is used to spread the inoculating bacteria over the surface of the agar. - Plastic sterile disposable spreaders are a suitable alternative to the glass spreaders that require sterilisation before and after use.

Answer 267

* At the very basic level, discs of antibiotics can be placed on agar in a Petri dish. * The agar is inoculated with a particular type of bacterium and the effect of the antibiotic (or antibiotics) on that strain of bacteria can be investigated.

Answer 268

Textbook page 40

Answer 269

An E-strip is a prepared strip that contains a concentration gradient of antibiotic (or antimicrobial compound) running the length of the strip.

Answer 270

* Alternatively, E-strips are a more sophisticated way of measuring the effect of different concentrations of antibiotic on bacteria. * The process involves placing the E-strip on the agar of a Petri dish that has been inoculated with a bacterium. * Following incubation (normally between 18-72 hours needed), and depending on the E-strip and microorganism used, a result similar to that in the diagram below can be observed.

Answer 271

The minimum antibiotic concentration that is necessary to inhibit bacterial growth.

Answer 272

Textbook page 40

Answer 273

Isolate single colonies of microbial cells, ie a pure culture of cells, all of which share the same parental cell.

Answer 274

1. Using an inoculating loop, spread the microorganisms over a small section of the agar in the Petri dish (the initial inoculation, stage 1). 2. Then, with a new/sterilised inoculating loop, 'streak' several lines of microorganism across the agar at an angle, taking care not to allow the separate 'lines' to overlap (stage 2). 3. Repeat stage 2 once or twice, making sure that a sterile loop is used on each occasion (stages 3 & 4). 4. Make a final single streak as shown (stage 5). 5. Incubate the Petri dish at a suitable temperature. After 24 hours or so it should be possible to identify isolated pure colonies (stage 6). Flow diagram on page 41

Answer 275

A range of defences against microorganisms.

Answer 276

Prevent decay and further loss in parts of plants, for example leaves, which become damaged in their natural environment.

Answer 277

Wood anemone, bluebell, lesser celandine, wild garlic and mint

Answer 278

Compounds that prevent or reduce fungal and/or bacterial growth

Answer 279

1. Grind up the leaves of each woodland plant and a small amount of water in separate mortars. 2. Prepare some agar plates (Petri dishes) and spread a fungus or bacterium culture on the plate using appropriate aseptic techniques. 3. Soak a small disk of filter paper with each plant extract and place on the agar in the Petri dish. 4. Incubate for 24-48 hours and compare results in the different Petri dishes. Alternatively, instead of comparing antimicrobial properties in different plants, it is possible to compare the effect of extract concentration, temperature of incubation and many other variables.