cells and the immune system Flashcards
(50 cards)
1
Q
Define the term, ‘immune system.’
A
- works through a system of recognition mechanisms which enable it to distinguish native cells from pathogens (foreign bodies) —> eliminate these pathogens
2
Q
Definitions
A
- pathogens = microorganisms that cause disease
- phagocytes = macrophages/neutrophils involved in phagocytosis which is immediate
- lymphocytes = B and T cells involved in longer responses
- T-cell - involved in cell mediated response
- B-cell = involved in humoral response
- antibodies = proteins that bind to antigens to form an antigen-antibody complex
3
Q
Describe what is meant by an antigen
A
- specific molecules found of the surfaces of all cells.
- when these molecules recognised as foreign by immune system - stimulate immune response and lead production of antibodies
- huge, - proteins have variety and highly specific tertiary structure
- variety of specific 3-D structure that distinguishes one cell from another
- specific tertiary structure - diff proteins to act as specific antigens
4
Q
What does antigens allow the immune system to identify?
A
- pathogens = organisms that causes disease. Pathogens have antigens on their surface - these are identified as foreign by immune system cells - respond to destroy pathogen
- abnormal body cells = cancerous cells have abnormal antigens on their surface, triggering immune response
- toxins = poisons - some produced by bacteria. Immune system respond to toxins as well as pathogens that release them
5
Q
What are the different types of blood groups?
A
ABO system:
A - anti-B antibodies
B - anti-A antibodies
AB - no antibodies
O - anti-A and anti-b antibodies
6
Q
What is the RhD antigen
A
- a protein on surface of RBCs.
- if its present, blood group RhD positive —> if its absent, blood group is RhD negative.
- whether negative/positive depends on how many copies of RhD antigen inherited
- negative —> if you don’t inherit any copies of RhD antigen from parents as its dominant
7
Q
What is meant by a blood transfusion?
A
- when you are given blood from someone else (donor) that’s life saving
- if you have shortage of RBC, cancer, severe bleeding.
- can replace blood lost, or replace liquid of cells found in blood
8
Q
What are the risks with a blood transfusion?
A
- if donor type doesn’t match receiver and antigens on RBCs not recognised by the recipient, the immune system will generate immune response as they reject foreign cells and attack them
- allergic reactions - result anaphylactic shock.
- bloodborne diseases.
9
Q
What are antigenic variation?
A
- DNA in a pathogen mutates frequently
- if mutation occurs in gene that codes for the antigen the primary structure of the antigen will change
- alters tertiary structure of antigen causing it to change shape
- as the antigens are a new shape - previous natural immunity to this pathogen no longer effective —> memory cells specific to only one type antigen
10
Q
How do lymphocytes recognise cells?
A
1) diff types of B lymphocyte in body - each one recognises a specific antigen
2) lymphocytes made when you are a foetus - only exposed on self cells
3) lymphocytes complementary to antigens on self cells will die or the production of them will be suppressed
4) prevent your body from attacking your own cells
5) the only remaining lymphocytes are complementary to non-self cells/pathogens
6) process repeats after birth in bone marrow —> any new lymphocytes made which complementary to self cells destroyed
11
Q
Describe what is meant buy a major histocompatibility complex (MHC)
A
- protein marker on self cells used to distinguish native cells from foreign bodies.
- enable immune system to be able to specifically attack foreign pathogens as well as abnormal cells
12
Q
What are the two types of MHC molecule?
A
MHC I
- found on normal body cells
- bind to endogenous antigens + display them on cell surface membrane - identified as self-cells to immune system.
- found on immunological cells + allow them to recognise each other and communicate with each other
MHC II
- found on immune system cells
- found specifically in immunological cells - macrophages, neutrophils, dendritic cells
- bind to foreign antigens to activate immune response against invading pathogen
13
Q
Explain the role of devil facial tumour disease
A
- aggressive non-viral, transmittable parasitic cancer that affects Tasmanian Devil
- small lumps in and around mouth develop into large tumours on face/neck.
- Tasmanian Devils are genetically close to each other causing genetic bottlenecking —> develop facial tumours
14
Q
Explain what is meant by ‘defence mechanisms’
A
- human body has range defences to protect itself from pathogens —> immediate defences like skin forming barrier to entry of pathogens
15
Q
What are some examples of non specific and specific defence mechanisms
A
Non specific —> physical barrier, phagocytosis
Specific —> cell-mediated responses, humoral responses involving B lymphocytes
16
Q
Antigen presenting cells
A
- they are any cell that presents a non-self antigen on their surface
- they are the hosts own cels
- can be : phagocytes, abnormal self-cells, cancer cells, non-self cells from a transplant, infected body cells
- can trigger cell mediate response
17
Q
Describe the roles of phagocytes
A
- WBCs produced in the bone marrow
- carry out phagocytosis (engulfment of pathogens)
- first cells to respond to immune system trigger inside body
- carry out non-specific immune response
- stored in bone marrow before distributed around body in the blood
- remove dead cells and invasive microorganisms
18
Q
What are the two main types of phagocyte?
A
- neutrophils
- macrophages
19
Q
What is the role of neutrophils?
A
- short acting, initiate immediate response
- travel throughout body and leave blood by squeezing though capillary walls to ‘patrol’ body tissues
- during infection: released in large numbers from their stores
20
Q
What is the role of macrophages?
A
- adaptive immune response.
- larger than neutrophils and long-lived cells
- move into organs —> after produced in bone marrow, macrophages travel in blood as monocytes which develop into macrophages once they leave blood
21
Q
Explain the process of phagocytosis
A
- Phagocyte attracted to pathogen by chemical products of pathogen. Moves towards pathogen along increasing conc gradient of chemoattractants
- Phagocyte recognises foreign antigen on a pathogen - recognise PAMPs through specialised receptors on cell surface membranes (PRRs) —> complementary to each other
- PRRs recognise + bind to a PAMP - activates the phagocyte - signals molecules like interferons help phagocyte activation
- Pathogen coated in molecules that coat pathogen so phagocytes bind called opsonins
- Phagocyte grows cytoplasmic extensions to engulf pathogen + internalises into cytoplasms by endocytosis
- Pathogen contains phagocytic vacuole in middle cytoplasm
- Lysosome fuses with phagocytic vacuole.
- Lysozymes from lysosomes hydrolyse pathogen
- Phagocyte absorbs digestive products. Hydrolysis products absorbed by phagocyte
- Phagocyte presents pathogen antigens by sticking antigens on its surface to activate other immune system cels —> act is as antigen-presenting cell
22
Q
Describe what are lymphocytes
A
- type of WBCs - specific immune response
- slower in action first but provide long-term immunity
- smaller than phagocytes
- large nucleus that fills most of cells
- produced in bone marrow by stem cells
23
Q
What are the two types of lymphocytes?
A
- T-lymphocytes (T cells)
- B-lymphocytes (B cells)
24
Q
Explain what is meant by T-cells?
A
- type of WBC, involved in cell-mediated response
- has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes —> activates T-celll
-T-lymphocytes leave bone marrrow to mature in the thymus. Mature T-lymphocytes have specific cell surface receptors called T cell receptors - specific to 1 antigen
- T-helper cells release cytokines called interleukin-2 that stimulates B-cells to divide next phase of immune response
25
Describe what occurs during cell mediated immunity - T CELLS
1. Antigens presented after phagocytosis, phagocyte is an antigen presenting cel
2. Helper t-cells have receptors on surface to attract antigens on antigen presenting cell
3. Complementary to each other. Once antigen attached to t-cell receptors —> activates helper T cells to divide by mitosis to replicate and are clones
4. Macrophage releases cytokines which stimulates T cell to release interleukin-2 which causes the proliferation of cytotoxic T cells and B CELLS
6. Cloned T cells differentiate into dif cells/stimulate dif cells:
—> activate B cells
—> stimulate phagocytosis
—> become T memory cells of specific antigen
—> cytotoxic T cells
26
What are cytotoxic T cells?
- destroy abnormal cells - T cells bind to MHC molecules of infected cells.
- release protein embeds into cell surface membrane of infected cell makes pores so movement of substances uncontrolled
- cause cell death as water enters the cell causing cytoplasms
27
What are B cells?
- B-cells type of WBCs
- covered with antibodies - proteins that bind to antigens to form an antigen-antibody complex
- has different shaped antibody on its membrane, so diff ones bind to diff shaped antigens
- B-cells respond to antigens by producing antibodies and memory cells
- involved in specific response - response to specific antigen
- humoral response - b cells and antibody response - humour
- activated when t helper cells bind to their class II MHC molecule
28
Explain what occurs during the humoral immune response - B CELLS
1. Antigens in blood from invading pathogens recognised by specific B-cells with correct antibodies. 1 b cells that has antibody on its surface
2. B-cell binds to complementary antigen forming antigen-antibody complex and takes it up by endocytosis
3. B-cells process the antigens + present them on its surface with class II MHC molecule
4. T-helper cells bind to these processed antigens + T-cell receptor and CD4 protein to recognise and bind to class II histocompatibility molecule onto b-cell
5. Stimulates B cells bind to divide by mitosis and differentiate to form a clones of identical B cells. Antibody molecule don’t leave B-lymphocyte cells, they remain in cell surface membrane —> each clone produces specific antibody -> monoclonal antibodies
29
B cells are able to divide by mitosis and differentiate into what types of cells?
- plasma cells
- memory cells
30
What are plasma cells?
secrete specific antibodies into blood plasma
- cloned plasma cells produce antibodies that’s complementary to antigen on pathogens surface and destroy pathogen
-plasma cells responsible for immediate defence of the body against infection
- production of antibodies/memory cells = primary immune response
31
What re memory cells?
- secondary immune response. Circulate in the blood and tissue fluid
- if encounter pathogen later date, they divide rapidly + develop into plasma cells and more memory cells
- memory cells provide long term immunity against original infection
- increased quantity of antibodies is secreted faster rate than in primary immune response.
32
Briefly describe the structure of antibodies
- antibodies have proteins that bind to antigens to form antigen-antibody complex
- soluble in blood/tissue fluid
- quaternary structure - 4 polypeptides chains —> 2 short chains (light), 2 long chains (heavy)
- variable region - complementary to specific antigen
- constant group -always the same. Antibodies are flexible
33
Explain the process of antibody agglutination
- antibody binds to antigens to form antigen-antibody complex
- antibodies flexible that bind to antigens and flex to bind to another antigen
- contain 2 antigen-binding sites means —> bind to 2 pathogens at same time —> become markers
- phagocytes engulf and digest pathogens at same time, makes phagocytosis more efficient as clump easier to locate than single pathogen/antigens
34
What’s the difference between the primary and secondary immune response
Primary
- plasma cells,
- occurs when foreign antigen enters body for the first time
- slow rate of antibody production = aren’t many B-cells produce specific antibody
- has symptoms
Secondary
- memory cells
- occurs when pathogen/antigens enter body again
- faster rate than- clonal selection happens faster + memory B cells divide rapidly into plasma cells + memory T cells divide
- no symptoms - quick response so pathogen destroyed before shown symptoms
35
What is meany by the term, ‘active immunity’
- immune system makes it own antibodies after being stimulated to an antigens and antibodies and memory cells produced
36
What’s the difference between natural and artificial active immunity
- natural refers to when you become immune after catching a disease as body creates own antibodies/memory cells
- artificial - when you become immune after you’ve been given a vaccination containing a harmless dose of antigen
37
What is meant by the term, ‘passive immunity.’
- you get given antibodies made by a different organism. Your immune system doesn’t produce any antibodies of its own.
38
What’s the difference between natural and artificial passive immunity?
- natural = when a baby becomes immune due to antibodies received from its mother - through placenta/breast milk
- artificial = become immune after injected with antibodies form someone else
39
What’s meant by the term, ‘vaccination’
- a dead/weakened version of the pathogen or pathogens antigens injected - form of active/artifical immunity
40
How does a vaccination work by?
1. Phagocytosis. Macrophage presents antigens on surface.
2. T helper cell with complementary receptor binds to antigen
3. Clones and triggers response of B cells. B cell with complementary antibody on its surface stimulated to go though clonal selection: clonal expansion + differentiation
4. Creates plasma cells and memory B-cells - primary response
5. Plasma cells secrete antibodies complementary to pathogens antigens.
6. Memory B-cells remain in blood so upon reinfection they divide by mitosis to produce plasma cells rapidly in large quantities to produce specific antibody to bind to specific antigens — AGGLUTINATION; encourage phagocytosis of pathogen to destroy it
41
What’s meant by the term, ‘herd immunity’?
- if large enough number of a population get vaccinated against a a specific pathogen, the pathogen cannot spread easily.
42
What type of people are vulnerable to herd immunity?
- too young as immune system isn’t developed enough to cope with vaccine.
- already ill
- have lowered immunity
43
Why may vaccinations not eliminate a disease?
- vaccination fails to induce immunity in certain individuals, like ppl with defective immune systems
- individuals may develop the disease after vaccination but their immunity levels high enough to prevent it. - harbour pathogen and reinfect others
- pathogen may mutate frequently, antigens change suddenly rather gradually. —> ineffective vaccines as new antigens on pathogens no longer recognised by immune system
- so many varieties of particular pathogen - impossible to develop vaccine that’s effective against them all
- pathogens ‘hide’ from body’s immune system - conceal themselves inside cell or living in places out of reach.
- ppl have may objections to vaccinations - religious, ethical or medical reasons
44
What are the ethics of potentially using vaccines?
- animal testing: production vaccines, development of new ones - uses animals. How acceptable is this?
- side effects - vaccines has side effects that may cause long term harm
- cost, health risks.
45
What are HIV and AIDS?
- HIV (human immunodeficiency virus) is a virus that affects the human immune system
- lead to AIDS (acquired immune deficiency syndrome) —> immune system deteriorates and eventually fails
- HIV = spread via sexual intercourse, infected bodily fluids and HIV-positive mother to foetus
46
Describe the structure of HIV
- retrovirus
- virus particle has a spherical structure
- on the outside is a lipid envelope which is made of membrane stolen from cell membrane of previous host cell
- has matrix
- has copies of attachment protein embedded into lipid envelope that help HIV attach to host helper T-cell
- inside envelope - capsid that encloses core
- core contains genetic material RNA - catalyses production of DNA from RNA needed for replication
47
What are some enzymes found in HIV core
- reverse transcriptase - catalyses production of DNA from RNA needed for replication
- integrate - inserts its viral DNA into DNA of host CD4 cell
- protease - breakers down larger precursor into smaller proteins —> combine with HIV genetic material to form new HIV virus
48
Explain the process of HIV replication
1) attachment protein on HIV binds to CD4 protein receptor on helper T cell
2) envelope fuses with cell-surface membrane which releases capsid into the helper T cell
3) capsid and matrix digested and releases RNA and enzymes of HIV into helper T cell
4) reverse transcriptase enzyme used to make complementary strand DNA from viral RNA template —> use host cell nucleotides to convert virus RNA into strand of DNA
5) DNA strand is reverse transcribed again to form double stranded DNA
6) an integrase enzyme grabs double helix + carries through nuclear pore into nucleus
7) DNA is transcribed. RNA polymerase from host cells creates messenger RNA. - contains instructions for new viral proteins
8) translation of HIV mRNA using cells protein synthesis mechanisms to make HIV particles
49
How does HIV cause symptoms of aids
HIV causes AIDS by killing/interfering with normal functioning helpers T cells
- HIV infects + kills helper T cells as it multiples rapid
- HIV replicates + viruses increases, helper T-cell count drops, leads to AIDS
- without sufficient helper T cells, immune system can’t stimulate B cells to produce antibodies - memory cells also infected/destroyed
- B plasma cells can’t secrete antibodies for agglutination + destruction of pathogens by phagocytosis
- immune system deteriorates. As result, body unable produce immune response + susceptible to infections
- infecting immune system = HIV prevents from functioning normally. - ill health and eventual death
50
Describe the initial infection of HIV + the symptoms of AIDS
- initial stage HIV infection causes flu-like symptoms
