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Biology AS > Immune System > Flashcards

Immune System Flashcards

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1
Q

Antigens

A
  • Glycoproteins
  • Found on the cell surface membrane of cells
  • Stimulate an immune response which produces antibodies
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2
Q

Lymphocytes

A
  • Involved in the immune system

- Detect the bodies on antigens (self) and foreign ones (non-self)

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3
Q

Immune System Identifies

A
  • Pathogens: organisms that cause disease
  • Abnormal body cells: pathogen infected/cancerous cells with abnormal antigens
  • Toxins: chemicals produced by bacteria
  • Non-self Material: e.g. cells from donors such as organs or blood
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4
Q

Phagocytes

A
  • White blood cell

- First cells to respond to an immune system trigger

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5
Q

Phagocytosis

A
  • Phagocyte recognises the non-self antigen on the pathogen
  • Engulfs pathogen into its phagocytic vacuole
  • Lysosomes fuse with the phagocytic vacuole
  • Hydrolytic enzymes (lysozyme) digest the pathogen
  • Phagocyte presents the pathogens antigens on it’s cell surface membrane
  • Becomes an antigen presenting cell (activates T-cells when they bind to the presented antigens)
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6
Q

T-Lymphocytes

A
  • White blood cell

- Involved in the cell mediated response

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7
Q

Helper T-cells

A
  • Have specific receptors
  • These are complementary to antigens on the antigen presenting cell
  • They release chemical signals that activate and stimulate phagocytes and B-cells
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8
Q

Cytotoxic T-cells

A
  • Kill host cells
  • By producing a protein called perforin
  • The protein makes holes in the cell membrane
  • Making it permeable to all substances
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9
Q

B-Lymphocytes

A
  • White blood cell

- Involved in the humoral response

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10
Q

B-cell Activation

A
  • Activated when a complementary antigen binds to their surface
  • Antigen enters the cell by endocytosis
  • B-cell presents the antigen on the surface so T-helper cells can bind to it
  • B-cell divides by mitosis
  • Forming either plasma cells or memory cells during clonal selection
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11
Q

Plasma Cells

A
  • Clones of B-cells

- Secrete antibodies specific to the antigen

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12
Q

Monoclonal Antibodies

A
  • Antibodies produced from a single B-cell
  • Bind to antigens on the surface of the pathogen
  • Forms antigen-antibody complexes
  • Have two binding sites so bind to two antigens at a time
  • Pathogens become clumped together [agglutination]
  • Leads to destruction of pathogens that carry this antigen in the body
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13
Q

Antibodies

A
  • Proteins produced by B-cells and secreted by plasma cells
  • Made up of chains of amino acids [heavy and light polypeptide chains]
  • Each antibody is specific; it has a variable region with a unique tertiary structure
  • This is complementary to one specific antigen
  • All antibodies have the same constant regions
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14
Q

Cellular Immune Response

A
  • Involves T-cells and phagocytes
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15
Q

Humoral Immune Response

A
  • Involves B-cells, clonal selection and production of monoclonal antibodies
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16
Q

Immunity

A
  • When the immune system can respond quickly to a second infection
17
Q

Primary Response

A
  • Pathogen enters the body for the first time
  • This activates the immune system
  • Response is slow; there are not enough B-cells
  • Therefore not enough antibodies needs to bind to antigens on the pathogen
  • Person shows symptoms
  • Memory cells are produced by T-cells and B-cells after the body is exposed to the antigen (stay in the body for a long time allowing the person to be immune)
18
Q

Memory Cells

A
  • Stay in the body for a long time allowing the person to be immune
  • Memory T-cells: remember the specific antigen on the pathogen and recognise it a second time
  • Memory B-cells: remember specific antibodies needed to bind to the antigen
19
Q

Secondary Response

A
  • During a second infection if the same pathogen enters the body
  • It’s antigens are recognised
  • Immune system is quicker so clonal selection occurs faster
  • Memory B-cells are activated and they divide into plasma cells producing the right antibody for the pathogen
  • Memory T-cells are activated and divide into the correct type of T-cells to kill the pathogen carrying the antigen
  • Secondary response removes the antigen before symptoms show; the body is immune to the pathogen
20
Q

Vaccines

A
  • Protect individuals and populations against disease
  • Reduce disease occurrence
  • Contain antigens which cause the body to produce memory cells against a particular antigen
  • Allowing for immunity without symptoms
  • The antigens are free or attached to a dead/attenuated (weakened) pathogen
21
Q

Successful Vaccine

A
  • Sufficient quantities for herd immunity (those unprotected are less likely to come in contact with the disease)
  • Few side effects
  • Means for producing, storing, transporting and administrating vaccines are available
  • Must be possible to vaccinate most of the population
22
Q

Antigenic Variation

A
  • Some pathogens can change their surface antigens
  • Making it difficult to develop vaccines against some pathogens
  • Therefore during a second infection memory cells produced from the first infection won’t recognise the new antigens
  • Primary response is carried out again and the person becomes ill as this takes time
23
Q

Active Immunity

A
  • Immunity you get when your immune system makes its own antibodies after exposure to antigen
  • Natural Active: becoming immune after infection
  • Artificial Active: becoming immune after getting a vaccination containing a harmless dose of the antigen
  • Requires: exposure to antigen, protection takes a while to develop, protection is long-term as memory cells are produced
24
Q

Passive Immunity

A
  • Immunity you get from being given antibodies made by a different organism; your immune system can’t produce it’s own
  • Natural Passive: a baby becomes immune by receiving antibodies from it’s mother through the placenta and breast milk
  • Artificial Passive: becoming immune by being injected with antibodies from someone else e.g. blood donations
  • Requires: no exposure to antigen, protection is immediate but short term, as antibodies are broken down and memory cells aren’t produced
25
Q

Targeting Drugs To A Cell Type [Cancer Cells]

A
  • Cancer cells have antigens called tumor markers (not found on normal body cells)
  • Monoclonal antibodies are made which can bind to the tumor markers
  • Anti-cancer drugs are attached to the antibodies
  • When an antibody come into contact with a cancer cell it binds to the tumor markers
  • This allows the anti-cancer drug to accumulate in the body where the cancer cells are located
  • Side effects of an antibody-based drug are lower; they accumulate near specific cells
26
Q

Targeting A Substance For Medical Diagnosis [Pregnancy Testing]

A
  • The hormone hCG is found in urine of pregnant women and detected by a pregnancy test
  • The application area has antibodies with a blue bead attached and the antibodies bind to hCG present in the urine
  • This forms an antigen-antibody complex
  • Urine moves up the stick and carries the beads to the test strip
  • There are immobilised antibodies which are complementary to hCG on the test strip
  • If hCG is present in the urine the hCG-antibody complex with the blue bead attached becomes concentrated and the test strip area turns blue
  • If no hCG is present the urine and beads pass through the test area without binding to anything so the colour does not change
27
Q

HIV

A
  • A virus that affects the immune system
  • Eventually leads to AIDS when helper T-cell numbers in the body reach a critically low level
  • HIV infects helper T-cells by using them as host cells for the virus
  • This weakens the immune system as helper T-cells are needed to send chemical signals for activating phagocytes, cytotoxic T-cells and B-cells
28
Q

Structure Of HIV

A
  • Spherical
  • Core containing genetic material (RNA) and proteins (Reverse Transcriptase)
  • Outer coating of protein called a capsid
  • Extra outer layer envelop with attachment protein sticking out (help the HIV attach to the host helper T-cells)
29
Q

Replication Of HIV

A
  • Replicates in host helper T-cell; it doesn’t have it’s own enzymes or ribosomes
  • Attachment proteins attach to a receptor molecule on the cell membrane of a host cell
  • Capsid is released into the host cell, it uncoats and releases genetic material (RNA) into the cell
  • Reverse Transcriptase makes a complementary strand of viral DNA from the viral RNA template
  • Double-stranded viral DNA forms and is inserted into human DNA
  • Host cell enzymes make viral proteins from the viral DNA that is now in the human DNA
  • Viral proteins assemble into new viruses which detach from the host cell and infect other cells in the body
30
Q

Symptoms Of HIV

A
  • During infect period HIV replicates quickly and produces flu like symptoms
  • Replication rate drops and symptoms stop [latency period]
  • After the latency period it becomes AIDS
  • Symptoms include minor infections e.g. respiratory
  • Immune cells decrease and there is more susceptibility to serious infections e.g. tuberculosis or toxoplasmosis
  • Death comes from the infections e.g. pneumonia as immune system cells are too low
31
Q

Antivirals

A
  • Slow the progression of HIV as there is no cure

- They are drugs that target the virus-specific enzymes that exist e.g. reverse transcriptase

32
Q

Antibiotics & Viruses

A
  • Antibiotics kill bacteria
  • By interfering with their metabolic reactions
  • Through targeting the bacterial enzymes and ribosomes used in these metabolic reactions
  • Viruses don’t have their own enzymes and ribosomes so antibiotics can’t inhibit them or their host cells (as these have human enzymes and ribosomes)
33
Q

ELISA Test

A
  • This is used to see if a patient has antibodies to a certain antigen or antigens to a certain antibody
  • Direct ELISA: uses a single strand of antibody that is complementary to the antigen being tested for
  • Indirect ELISA: uses two different antibodies
34
Q

ELISA Test For HIV

A
  • Indirect
  • HIV antigen is bound to bottom of well plate
  • Patient blood plasma is added to the well
  • If HIV specific antibodies are present in the blood they bind to the antigen in the well
  • Well is washed out to remove unbound antibodies
  • Second antibody is added to the well as has a specific enzyme attached to it
  • Second antibody binds to the HIV specific primary antibody if it is present in the well
  • Well is washed out to remove unbound secondary antibody
  • A solution with a substrate that can react with the enzyme attached to the secondary antibody is added to produce a coloured product

Biology AS (7 decks)

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