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Biology Year 13 > The Response To Infection > Flashcards

The Response To Infection Flashcards

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1
Q

What’s key to cell recognition?

A

Th genetically determined protein molecules on the surface membrane of cells. These proteins include glycoproteins

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2
Q

What are antigens?

A

Glycoproteins, proteins or carbohydrates on the surface of cells, toxins produced by bacteria and fungal pathogens and some whole viruses and bacteria that are recognised by white blood cells during the specific immune responses to infection. They stimulate the production of an antibody

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3
Q

What is key to the working of the immune system?

A

The ability of the body to distinguish between it’s own cells (‘self’) and foreign cells or organisms (‘non self’)

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4
Q

What is a non specific immune response?

A

A response that is triggered by any pathogen

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5
Q

What is a specific immune response?

A

One that is specific to particular pathogens

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6
Q

What are non-specific responses to infection triggered by?

A

Body cells breaking down and releasing chemicals and by pathogens that have been labelled by the specific immune system

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7
Q

What is inflammation?

A

A common, non-specific response to infection involving the release of histamines from the mast cells and basophils, causing the blood vessels to dilate, giving local heat, redness and swelling

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8
Q

What are histamines?

A

Chemicals released by the tissues in response to an allergic reaction

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9
Q

When does inflammation occur?

A

When an infection is relatively localised

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10
Q

What happens in an inflammatory response?

A

Special cells called mast cells are found in the connective tissue below the skin and around the blood vessels. When this tissue is damaged these mast cells and basophils release chemicals known as histamines. Histamines cause the blood vessels in the area, particularly the arterioles to dilate causing heat and redness. The locally raised temperature reduces the effectiveness of pathogen reproduction in that area. The histamines also make the walls of the capillaries leaky as the cells forming the walls seperate slightly. As a result fluid (plasma) containung leucocytes (mainly neutrophils) and antibodies is forced out of the capillaries causing swelling and often pain. The antibodies disable the pathogens and the macrophages and neutrophils destroy them by phagocytosis

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11
Q

What us a fairly common symptom of a more widespread infection?

A

A rash which is a form of inflammation or tissye damage that particularly affects the skin causing red spots or patches

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12
Q

What are antibodies?

A

An antibody is a glycoprotien that is produced in respinse to a specific antigen

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13
Q

An early common, non specific response to infection is a fever. How does this response come about?

A

When a pathogen infects the body it causes the hypothalamus to reset to a higher body temperatue

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14
Q

How does a raised body temperature help combat infection?

A
  • many pathogens reproduce most quickly at 37°c or lower. Therefore a raised temperature will reduce the ability of many pathogens to reproduce effectively and so they will cause less damage
  • the specific response system (immune system) works better at higher temperatures and so will be more successful at combating the infection if the temperature is raised
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15
Q

How do fevers work with bacterial infections and with viral infections?

A
  • in a bacterial infection the temperature riaes steadily and remains fairly high until treatment is successful or the body overcomes the infection
  • in viral infecrions the temperature tends to spike shooting up high every time the viruses burst out of the cells and then dropping down to normal again
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16
Q

When get fevers be damaging or even fatal?

A

If your body rises above 40°c the denaturation of some enzymes takes place and you may suffer permenant tissye damage. If the temperature is not lowered fairly quickly death may result. Sweating is often associated with fever as the body sweats in response to the high temperature and as a coding mechanism. If the fluid and electrolytes lost in the sweat are not replaced, dangerous dehydration and even death can result

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17
Q

What are the two main types of phagocytes?

A
  • neutrophils are granylocytes and make up 70% of the leucocytes in the blood. Each neutrophil can only ingest a few pathogens before it dies. They cannot renew their lysosomes so once the enzymes are used up in the cell they cannot break down any more pathogens
  • macrophages are derived from monocytes which are agranulocytes. They make up about 4% of the leuocoytes in the blood. However the monocytes migrate to the tissues and become macrophages so there are large numbers of macrophages in the tissues. Macrophages have an enourmous capacity for ingesting pathogens because unlike neutrophils they can renew their lysosomes so last much longer. They accumulate at the site of an infection to attack the invading pathogens
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18
Q

How do phagocytes work?

A

They engulf the pathogen. The pathogen is enclosed in a vesicle called a phagosome. The phagosome then fuses with a lysosome. The enzymes in the lysosome break down the pathogen. The phagocytes can sometimes be seen as pus - a build up of dead cells which are mainly neutrophils. The pus may ooze out of a wound or spot or it may be reabsorbed by the body. When phagocytes have engulfed a pathogen they produce chemicals called cytokines in the surrounding tissues.

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19
Q

What is a phagosome?

A

The vesicle in which a pathogen is enclosed in a phagocyte

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20
Q

What are cytokines?

A

Cell signalling molecules with several roles in the immune system, including stimulating other pathogens to move to the infection site and raising body temperature

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21
Q

What are opsonins?

A

Chemucals which bind to pathogens and label them so they are more easily recognised by the receptors of the membranes of the phagocytes

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22
Q

What is the immune response?

A

The specific response of the body to invasion by pathogens

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23
Q

What are the four key characterisitics of the immune system of the body?

A
  • It can distinguish self from non-self
  • it is specific - responds to specific foreign cells
  • it is diverse - it can recognise an estimated 10 millipn different antigens
  • it has immunological memory - once you have met and responded to a pathogen you can respond rapidly if you meet it again
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24
Q

What are lymphocytes?

A

Granulocytes, made in the white bone marrow of the long bones, that make up the main cellular components of the immune system

25
Q

What are B cells?

A

Lymphocytes made in the bone marrow which are found both in the lymph glands amd free in the body once they are mature

26
Q

What are immunoglobulins?

A

Antibodies

27
Q

Give features of B cells

A
  • they have membrane bound globular receptor proteins on their cell surface membrane that are identical to the antibodies they will later produce
  • around 10p million B cells are formed as the embryo grows, each with a different membrane bound antibody. Each then divides to form a clone of cells giving a baby an immune system with the potential to recognise and tackle an enormous range of pathogens
28
Q

When a B cell binds yo an antigen what types of B cell are produced?

A
  • B effector cells - these cells divide to form the plasma cell clones
  • plasma cells - these produce antibodies to particular antigens at a rate of around 2000 antibodies per second
  • B memory cells - these provide the immumological memory to a specific antigen, allowing the body to respond very rapdily if you encounter a pathogen carrying the same antigen again
29
Q

What are T cells?

A

Lymphocytes made in the bone marrow that mature and become active in the thymus gland

30
Q

Give features of T cells?

A
  • the surface of each T cell displays thousands of identical T - cell receptors.
  • T cell receptors bind to antigens on infected body cells and then further types of T cells are produced and play different roles in the immune response
31
Q

What are the further types of T cells that are produced then the T-cell receptors bund to the antigens of infected body cells?

A
  • T killer cells produce chemicals to destroy infected body cells
  • T helper cells activate the plasma cells to produce antibodies against the antigens on a particular pathogen and also secrete opsonins to label the pathogen for phagocytosis by white blood cells
  • T memory cells are very long lived cells that make up part of the immunological memory. When they meet a pathogen for the second time they divide rapidly forming a large clone of T killer cells which then quickly destroy the pathogen
32
Q

What are major histocompatibility complex (MHC) proteins?

A

Proteins that display antigens on the cell surface membrane

33
Q

What does the humoral response of the immune system do?

A

Reacts to antigens found outisde the body cells including antigens on pathogens such as bacteria and fungi and to antigen presenting body cells. The humoral response results in the production of antibodies which are not attached to the cells but are carried through the body in the blood and tissue fluid. Although B cells produce the antibodies T cells are first involved in activating the B cells. The humoral response consists of two main stages: the T helper activation stage and the effector stage

34
Q

What happens in the T helper activation stage of the humoral response?

A

When a pathogen enters the body, chemicals are produced that attract the phagocytes, including macrophages and neutrophils. When a neurtophil engulfs a bacterium it destroys it in about 10 mins. Macrophages take longer but do more, preparing the way for the specific immune system. The macrophage seperates off the antigens from the digested pathogen and combines them with the major histocompatibility complex. The complexes move to the surface of the macrophage cell outer membrane. The macrophage with these antigen/MHC protein complexes displayed on the cell surface is now known as an antigen - presenting cell (APC)

The next step involves T cells which gave receptors on the outer membrane that bind to the specific antigen of the antigen/ MHC complex on the APC. The binding of the T cell with the APC triggers the T cell to reproduce and form a clone of cells. Most of these cells beomce active T helper cells which are then used in the rest of the immune systen. The remainer of the cloned cells form inactive T memory cells which remain in the body and rapidly becone active if the same antigen is encountered again

35
Q

What happens in the effector stage?

A

Some of the millions of different B cells will have ommunoglobulins of their surface that are specific for the antigen presented by the pathogen and will bind to it. The B cell then engulfs the whole pathogen by endocytosis. The vesicle formed fuses with a lysosome and enzymes break fown the pathogen to leave fragments of processed antigen. These fragments become attached to MHC proteine with the cell and the MHC/antigen complex is transported to the cell surface membrane where it is displayed.

A T helper cell from the active clone produced in the T helper activation stage recognises the specific antigen displayed on the MHC complex on the B cell and binds to it. This triggers the release ot cytokines from the T helper cell which stimulate the B cells to divide and form clones of identical cells. This is known as clonal selection. New clones of B effector and memory cells are produced. The B effector cells differentiate to form plasma cells (plasma cell clones).

The plasma cells produce large amounts of antibodies that are identical to the immunoglobin of the orignial parent B cell.

36
Q

What are the ways in which antibodies can cause destruction?

A
  • agglutination: when antibodies bind to the antigens on pathogens, the microorganisms agglutinate or clump together. This helps to prevent them spreading through the body and also makes it easier for them to be engulfed by phagocytes
  • Opsonisation: the antibody acts as an opsonin, a chemical which makes an antigen or pathogen more easily recognised by phagocytes
  • neutralisation: antibodies neutralise the effects of bacterial toxins by binding to them
37
Q

Give features of plasma cells

A
  • they live for only a few days bu can produce up to 2000 antibody molevules per second
  • they have an extensive ER and many ribosomes which are adaptations for their role in producing large quantities of protein antibodies.
  • the antibodies remain in the blood for varying lengths of time and the memory cells may stay in the blood for years or even life
38
Q

What happens in a cell mediated response?

A

When the pathogen is inside the host cells and the humoral response is not effective. It involves T killer cells which respond to specific antigens. T lymphocytes respond to cells that have been changed in some way, e.g. to cells infected by a virus, antigen presenting cells, cells changed by mutation to produce cancer cells or the cells of a transplanted organ. When a body cell is infected with a bacterium or virus the pathogen is digested and the surfave antigens become bound to an MHC in a similar process to that seen in macrophages. As a result the body cell effectively becomes an APC.

T killet cells in the blood have a wide range of complementary receptor proteins on the surfave of their cell surface membrane. T killer cells bind to matching antigen/ MHC complex on the surface of the body cell. If the T cells are then exposed to cytokines from an active T helper cell, produced through T helper cell activation they undergo a rapid series of cell divisions to produce a clone of identical active T killer cells which can all bind to infected body cells. The T killer cells release enzymes that make pores form in the membrane of the infected cells. This allows the free entry of water and ions so the cells swell and burst. Any pathogens that are released intact are labelled with antibodies produced by plasma cells and then destroyed. T killer memory cells are also produced

39
Q

Why do we get the symptoms of disease?

A

Because it can take days or even a week for the primary immune response to become fully active against a particular pathogen. This is why we get symptoms of disease

40
Q

What is the primary immune response?

A

It involves the production of antibodies by plasma cells produced from the B effector cells and the activation to T killer cells

41
Q

What is the secondary immune response?

A

Whe the B-cell APC divides it also produces B memory cells. B memory cells are very long lived and are important in allowing the body to respond rapidly to a second invasion by the dame antigen. B memory cells help to produce antibodies very quickly

At the same time as a clone of active T killer cells are formed some cloned T cells become T memory cells. These persist om the blood so that the body can produce a rapid response it the same pathogen invades again. These memory cells release a flood of active T killer cells to engulf and destroy infected cells

42
Q

What is natural active immunity?

A

Is when the body produces its own antibodies to an antigen encountered naturally

43
Q

What is natural passive immunity?

A

When antibodies made by the mother are passed to the baby via the placenta or breast milk

44
Q

What is immunisation?

A

The process of protecting people from infection by giving them passive or artificial immunity. It enables you to develop immunity by exposing your immune system to antigens in a safe way that does not put you at risk of developing the disease so that antibodies and memory cells can be prepared for meeting the real thing

45
Q

What is vaccination?

A

The introduction of harmless forms of organisms or antigens by injection or mouth to produce artificial immunity

46
Q

What is artificial passive immunity?

A

When antibodies are extracted from one individual and injected into another. The antibodies may be from a person who is already immune to a disease. This doesn’t create long term immunity because the antibodies are gradually broken down and not replaced but can be very valuable if someone has been exposed to a rapidly acting antigen such as tetanus

47
Q

What is artificial passive immunity?

A

When antibodies are extracted from one individual and injected into another. The antibodies may be from a person who is already immune to a disease. This doesn’t create long term immunity because the antibodies are gradually broken down and not replaced but can be very valuable if someone has been exposed to a rapidly acting antigen such as tetanus

48
Q

What is artificial active immunity and what is used to create it?

A

Small amounts of antigen (known as the vaccine) are used to produce immunity in a person. The pathogen is made non-infective without reducing it’s ability to act as an antigen. This can be done in a number of ways. If it is a toxin that causes the symptoms, a detoxified form with one or more chemical groups will be injected. Sometimes inactivated viruses or dead bacteria are used as vaccines and in other cases qttenuated pathogend are used. Increasingly fragments of the outer coats of viruses and bacteria or even DNA segments are used as vaccines. Your immune system will produce antibodies against the antigen and appropriate memory cells will be formed without you becoming ill.

49
Q

What are attenuated pathogens?

A

Viable pathogens that have been modified so that they don’t cause the disease but still have an immune response that results in the production of antibodies and immunity

50
Q

What are the features that made the eradication of smallpox possible?

A

It was very recognisable, had no non-human hosts, a long incubation period and a visible scar as evidence of immunisation

51
Q

What is elimination?

A

Where the disease disappears but the pathogen remains in animals, the environment or in mild infections which are mot recognised and so immunisation must continue even when no clinical cases are being seen.

52
Q

What does it mean when a disease is controlled?

A

It occurs but not frequently enough to be a significant health problem

53
Q

What is herd immunity?

A

When a high proportion of a population is immune to a pathogen, usually by vaccination, lowering the rism of infection to all, including those not vaccinated as they are less likely to encounter the pathogen

54
Q

Who are the people that may not be able to be vaccinated?

A

Very young babies, very old people, people with comprimised immune systems or people who are very ill with other diseases

55
Q

What does the percentage of the population that needs to be vaccinated to give herd immunity depend on?

A

Factors such as how the disease is spread and how infectious it is

56
Q

What does the percentage of the population that needs to be vaccinated to give herd immunity depend on?

A

Factors such as how the disease is spread and how infectious it is

57
Q

What are the pros of vaccination programmes?

A
  • the child and the adult it grows into is protected against diseases that could otherwise disable or kill it
  • society benefits as the potential pool of infection is reduced with every vaccinated child through herd immunity, protecting children that can’t be vaccinated because of allergies of immune system diseases
  • the cost of treating serious diseases and caring for those left permenantly damaged by them is kept to a minimum for a relatively small price (vaccines are quite cheap)
58
Q

What are the cons of vaccination?

A
  • some of the live, attenuated vaccines are cultures in egss to which a small number of children may suffer a violent allergic reaction. To avoid this children wuth egg allergies are not given vaccines grown in eggs and are protected by herd immunity
  • a tiny minority of children become extremely ill after a vaccination with what may be an extreme immune response. Some of these children may die and others have been left severely brain damaged. It is very difficult to prove a direct link between the vaccine and the damage to a child because all children can get serious illnesses that affect them rapidly
  • some scientists have suggested that mass vaccination programmes are linked to the recent rise in childhood asthma and allergies
  • some vaccines such as rubella for boys are given more for the benefit of society than the direct benefit of the child. When girls are vaccinated against cervical cancer, it benefits both individuals and society but if boys are vaccinated the main benefit is to society

Biology Year 13 (16 decks)

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