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immunology Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are antigens?

A

foreign proteins that can generate an immune response when detected by the body
found on the surface of all body cells

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2
Q

what is an antigen presenting cell?

A

any cell that presents a non-self antigen on its surface

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3
Q

what are phagocytes responsible for?

A

removing dead cells and invasive microorganisms

carry out a non-specific immune response

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4
Q

what is the name for antigens that aren’t normally found in the body?

A

foreign antigens - these are the antigens the immune system responds to

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5
Q

what are pathogens?

A

organisms that cause disease –> immune system respond to destroy the pathogen.

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6
Q

what are abnormal body cells?

A

cancerous or pathogen-infected cells have abnormal antigens on their surface which triggers an immune response

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7
Q

what are toxins?

A

poisonous molecules not cells

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8
Q

how does the immune system identify cells from other individuals from the same species?

A

when you receive cells from another person from an organ transplant, those cells will have antigens different to your own. the foreign antigens trigger an immune response which leads to the rejection of transplanted organs

for blood transfusions, if the blood donated has A or B antigens that aren’t recognised by the recipient’s immune system they will generate an immune response

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9
Q

first stage of the immune response: phagocytosis

A
  1. a phagocyte recognises the foreign antigens on a pathogen and moves towards the pathogen along a concentration gradient
  2. the cytoplasm of the phagocyte moves round the pathogen, engulfing it
  3. pathogen is contained inside a phagocytic vacuole in the cytoplasm of the phagocyte
  4. lysosome fuses with the phagocytic vacuole. lysozymes break down the pathogen
  5. phagocyte presents the pathogen’s antigens - sticks the antigens on its surface to activate other immune cells
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10
Q

second stage of the immune respose: T-cells

A

T cells have receptor proteins on its surface that bind to complimentary antigens presented to it by phagocytes, this activates T cells
helper T cells release chemical signals which activate and stimulate phagocytes
cytotoxic T cells kill abnormal and foreign cells
T cells activate B-cells which release antibodies

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11
Q

what do cytotoxic T cells do?

A
  • destroy abnormal or foreign cells
  • release a protein, perforin which embeds in the cell surface membrane and makes a pore so any substance can enter or leave cell
  • causes cell death
  • most common in viral infections
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12
Q

third stage of the immune response: B-cells

A

B-cells are covered with antibodies (proteins that bind to antigens) to form an antigen-antibody complex
when the antibody meets a complementary shaped antigen, it binds to it. this and the substance released from helper T-cells activate the B-cells –> CLONAL SELECTION
the activated B-cells divide into plasma cells

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13
Q

fourth stage of the immune response: antibody production

A

plasma cells secrete loads of antibodies specific to the antigen –> MONOCLONAL ANTIBODIES
these bind to the surface of the pathogen to form lots of antigen-antibody complexes
antibody has 2 binding sites so can bind to 2 pathogens, pathogens clump together –> AGGLUTINATION

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14
Q

describe the structure of an antibody

A
  • proteins - made up of chains of amino acids
  • specificity of an antibody depends on its variable regions which form the antigen binding sites. binding sites are different in all antibodies
  • each antibody has a variable region with a unique tertiary structure
  • all antibodies have the same constant region
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15
Q

what forms a cellular response?

A

T-cells and other immune system cells that they interact with

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16
Q

what forms a humoral response?

A

B-cells, clonal selection and the production of monoclonal antibodies

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17
Q

what is a primary immune response?

A
  • when an antigen enters the body, activates immune system
  • slow because there aren’t many B-cells that can make the antibody needed to bind the antigen
  • after being exposed to an antigen, T- and B-cells produce memory cells
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18
Q

what is the difference between a memory T- and B-cell?

A

memory T-cell remembers the specific antigen and will recognise it a second time round
memory B-cells record specific antibodies needed to bind the antigen

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19
Q

what is a secondary immune response?

A

if the same pathogen enters the body again, immune system will produce a quicker, stronger immune response
clonal selection happens faster

20
Q

what is clonal selection?

A

when the antibody meets a complementary shaped antigen, it binds to it.

21
Q

what is active immunity?

A

immune system makes its own antiboides after being stimulated by an antigen
natural - becoming immune after catching a disease
artificial - becoming immune after you’ve been given a vaccination containing a harmless dose of antigen

22
Q

what is passive immunity?

A

immunity you get from being given antibodies made by a different organism
natural - baby becomes immune due to the antibodies it receives from its mother, through placenta and breast milk
artificial - becoming immune after being injected with antibodies from someone else

23
Q

what are some differences between active and passive immunity?

A

active immunity:
- requires exposure to antigen
- takes a while for protection to develop
- memory cells are produced
- protection is long term because antibody is produced in response to complementary antigen being present in the body

24
Q

what is herd immunity?

A

if a person is vaccinated against a particular pathogen, it reduces the occurrence of the disease. those not vaccinated are also less likely to catch the disease as there are fewer people to catch it from

25
Q

what is antigenic variation?

A

when pathogens change their surface antigens
different antigens are formed due to changes in the gene of a pathogen

26
Q

what is the ELISA test?

A

allows you to see if a patient has any antibodies to a certain antigen or any antigen to a certain antibody
- an antibody is used which has an enzyme attached to it. enzyme can react with a substrate to produce a coloured product.
- this causes the solution in the reaction vessel to change colour
- if there’s a colour change then the antigen or antibody of interest is present in the sample being tested

27
Q

how does a direct ELISA work?

teardrop

A

Target antigen coated on a plate - bind to bottom of test plate
Enzyme-linked antibody added - detection antibody with attached enzyme which is complimentary to the antigen of interest is added
Antigen-antibody complexes form - antibody binds to immobilised antigen
Reaction occurs with substrate - rinse excess antibody and add substrate
Detection of coloured product - intensity of colour is directly proportional to amount of antigen
Results interpreted - compare to determine concentration of target antigen
Output recorded
Positive control used - to ensure test is working properly

28
Q

how does an indirect ELISA work?

A

using two different antibodies
1. in the test, HIV antigens are present and fixed down in a well plate
2. blood sample is added, any HIV antibodies bind and the sample is washed to remove unbound antibodies
3. antibody-enzyme complex is added which binds to the first antibody. sample is washed to remove any unbound antibodies
4. substrate is added. enzyme acts on the substrate. as a result, colour of the solution changes

29
Q

what is HIV?

A

virus that affects the human immune system. eventually leads to AIDS. AIDS is a condition where the immune system deteriorates and eventually fails. person with AIDS becomes more vulnerable to other infections

30
Q

HIV host cells

A

HIV infects and kills T helper cells which acts as host cells for the virus

31
Q

what do helper T cells do?

A

send chemical signals that activate phagocytes, cytotoxic T-cells and B-cells

32
Q

what would happen if there aren’t enough T cells?

A

the immune system would not be able to carry out an immune response because other immune system cells don’t behave as they should

33
Q

describe the initial infection of HIV

A

HIV replicates rapidly and the infected person experiences severe flu-like symptoms. HIV replication then drops to a lower level and this is the LATENCY PERIOD. during this period, the infected person does not experience any symptoms

34
Q

what are some symptoms of AIDS?

A

initial symptoms of AIDS include minor infections of mucous membrane and recurring respiratory infections

35
Q

what happens as AIDS progresses?

A

the number of immune system cells decreases further. patients become more susceptible to serious infections like tuberculosis

36
Q

what happens in the late stages of AIDS?

A

patients have a very low number of immune system cells and can develop a range of serious infections like toxoplasmosis of the brain (parasite infection)

37
Q

what are some factors affecting the progression of HIV?

A

existing infections, strain of HIV, age, access to healthcare

38
Q

describe the structure of HIV

A

spherical structure, made up of a core containing genetic material (RNA) and some proteins including reverse transcriptase Outer coating called a capsid and an extra outer layer called an envelope which is amde from a membrane stolen from the cell membrane of a previous host cell. attachemtn proteins stick out from the envelope to help HIV attach to the host helper T cell

39
Q

how does HIV replicate?

a radiant rainbow helps viruses

A

Attachment proteins attach to receptors on helper T-cells such as CD4
RNA enters the host T-cell due to capsid uncoating and releasing genetic material
Reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template
Host cell enzymes are used to make viral proteins from viral DNA found within the human DNA
Virus is assembled and released

40
Q

how is HIV replicated once inside helper T-cells?

rent

A

Reverse transciptase converts HIV RNA into DNA
Entry of DNA into helper T-cells
Nucleic acid (DNA) is transcribed into RNA
Translation of RNA into viral proteins

41
Q

why are antibiotics ineffective for curing viruses?

A

antibiotics kill bacteria by interfering with their **metabolic reactions **. they target the bacterial enzymes and ribosomes used in these reactions
viruses don’t have their own enzymes or ribosomes, instead they use the one in the host’s cell. because human viruses use human enzymes to replicate, antibiotic can’t inhibit them because they don’t target human processes
antiviral drugs are designed to target the few virus-specific enzymes that exist

42
Q

how can you control HIV infection?

A

antiviral drugs can be used to slow down the progression of HIV

43
Q

describe the role of a neutrophil

A
  • travel throughout the body and leave by squeezing through capillary walls to ‘patrol’ body tissues
  • during an infection, they are released in large numbers
  • short-lived cells
44
Q

what is the mode of action of a neutrophil?

A
  • chemicals released by pathogen attract neutrophils to where pathogen is located (response to chemical stimuli - **CHEMOTAXIS **)
  • neutrophil moves towards pathogen
  • antibodies stimulate neutrophils to attack pathogen –> neutrophils have receptor proteins which recognises antibody
  • once attached, cell surface membrane extends out and around pathogen, engulfing it (now within a phagocytic vacuole) - endocytosis
  • neutrophil secretes digestive enzymes which destroy pathogen (from lysosome)
  • after killing and digesting pathogen, neutrophil dies
45
Q

describe the role of a macrophage

A
  • larger, longer-lived cells
  • move to organs e.g. lungs, liver… instead of remaining in blood
  • after being produced, they travel in the blood as monocytes –> develop after going to organ
46
Q

describe the mode of action of a macrophage

A
  • do not destroy pathogen completely
  • instead, they cut the pathogen up do they can display antigens of the pathogens on their surface
  • displayed antigens are recognised by lymphocytes
47
Q

outline the cell mediated response

A
  • once pathogen has been engulfed and digested by a phagocyte, antigens are positioned on the cell surface - antigen presenting cell
  • helper T cells have receptors on surface which attach to the antigens
  • once attached, activates T cells to divide by mitosis to make large numbers of clones
  • cloned helper T cells differentiate into different cells - some become macrophages, memory cells or cytotoix cells

Biology (8 decks)

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