5: Cell recognition and the immune system Flashcards
(120 cards)
1
Q
What is an infection?
A
Interaction between a pathogen and the body’s various defence mechanisms
2
Q
What is a pathogen?
A
Disease causing organism
3
Q
What type of cells form the responses of the body to pathogens?
A
Lymphocytes
4
Q
What type of lymphocytes and responses are there?
A
T lymphocytes - cause cell-mediated responses
B lymphocytes - cause humoral responses
5
Q
Why is it important a cell can be recognised as the body’s own cells?
A
To prevent the lymphocytes from destroying their own cells
6
Q
What molecules allow lymphocytes to recognise cells?
A
Proteins - as there is a variety of specific 3D tertiary structure
7
Q
What can the immune system identify?
A
Pathogens
Non-self materials from other organisms
Toxins produced by pathogens
Abnormal body cells such as cancer cells
8
Q
How is the identification of non-self cells disadvantageous?
A
Organ transplants as immune system wants to destroy these cells
This causes rejection of the tissue
9
Q
What is done to prevent tissue rejection?
A
Donor tissue normally matched as close to recipient
Immunosuppressant drugs lowering the response
10
Q
What are the best matches of tissues?
A
Relatives that are genetically close
11
Q
What are the two different types of defence mechanism?
A
Non-specific - response is immediate and same for all pathogens
Specific - response is slower and specific to each pathogen
12
Q
Why is there a good chance that there is a specific lymphocyte for a pathogen?
A
10 million different types of lymphocytes - good chance one will have the complementary protein shape
13
Q
Are the lymphocytes produced in response to pathogens?
A
Not in response, they are already there
14
Q
How do lymphocytes recognise the body’s cells?
A
In the fetus, lymphocytes constantly collide with different cells
Lymphocytes that have complementary shapes with the body’s cells die or are suppressed
Only ones left fight non-self materials
15
Q
Where are lymphocytes produced?
A
Bone marrow
16
Q
What happens in adult cells to prevent the destruction of self cells?
A
If lymphocytes show an immune response to self cells they undergo apoptosis (cell death)
This prevents them maturing and means no more of this type will form
17
Q
What is a self-antigen?
A
Antigens found on the surface of a self cell
18
Q
What is apoptosis?
A
Programmed cell death
19
Q
What are the two types of non-specific defence mechanisms?
A
Physical barrier
Phagocytosis
20
Q
What are the two types of specific defence mechanisms?
A
Cell-mediated response (T lymphocytes) Humoral response (B lymphocytes)
21
Q
What are some examples of physical barriers?
A
Skin - prevents entry of some pathogens
Nose/throat/digestive tract - membrane lining secretes sticky mucus trapping microbes
22
Q
What is the first line of defence?
A
Physical and chemical barriers
23
Q
What are some examples of chemical barriers?
A
Eyes - tears have lysozyme enzyme kills bacteria
Ear - wax has antimicrobial properties
Stomach - hydrochloric acid kills bacteria
24
Q
What are the two types of white blood cell?
A
Lymphocytes and Phagocytes
25
What is the function of phagocytes?
Ingest and destroy pathogens before it can cause harm (phagocytosis)
26
What is the second line of defence?
Phagocytosis
27
Explain the process of phagocytosis
Phagocytes attracted to pathogen by their chemical products
Receptors on phagocytes recognise and attach to chemicals on the surface of the pathogen
They engulf the pathogen to form a vesicle (phagosome)
Lysosomes fuse with vesicle and release lysozymes which destroy the pathogen
Soluble products are assimilated into cytoplasm of phagocyte
28
How do lysozymes affect pathogens?
Hydrolysis of cell wall, means it produces small soluble products
29
What is an Erythrocyte?
Red blood cell
30
What is a leukocyte?
White blood cell
31
What is an autoimmune disease?
When lymphocytes think self cells are pathogens and attack them
E.g. Type 1 diabetes
32
What is the innate system?
Physical barriers
Inflammation
Innate leukocytes (phagocytes)
33
What is the advantage of the non-specific response?
Immediate response
34
What is the advantage of a specific response?
Specific to each epitope
35
What is an epitope?
Specific area on a specific antigen
36
What are the two branches of the acquired immune system?
Natural
| Artificial
37
What are the two types of artificial acquired responses?
Active - immunisation/vaccination
| Passive - antibody transfer
38
What are the two types of natural acquired immune responses?
Active - cell mediated or humoral
| Passive - maternal
39
How is an element of the acquired immune system maternal?
Antibodies through placenta and milk
| Same environment makes it effective
40
What is immunity?
Ability to resist an infection from pathogen or toxins
41
What is an antigen?
Molecule that is recognised by the adaptive immune system via antigen receptors such as antibodies
42
What is assimilation?
Broken down products are used in the cell
43
Where are lymphocytes made and matured?
Made in bone marrow
B - matured in bone marrow
T - matured in thymus gland
44
Where is the thymus gland?
Behind the sternum
45
What are the two types of B lymphocytes?
Plasma cells
| B memory cells
46
What are the two major types of T lymphocytes?
T helper
| T cytotoxic
47
What are the types of T cytotoxic cells?
Active
| Memory
48
What are the types of T helper cells?
Active
| Memory
49
What is the humoral response?
Production of antibodies by B lymphocytes
50
How is T helper cell activated?
Presented antigen on self cells
Non-self non-pathogenic cells
Cancerous cells which present abnormal antigens
51
What happens when a T helper cell is activated?
Mitotic cloning & cytokine released
Activate: cytotoxic T cells, phagoytes, B lymphocytes
Produces some T Helper memory cells
52
How do cytotoxic T cells work?
They bind to the pathogenic cell and release perforin in to the cell
This ruptures the cell wall, causing water to rush in and cause cell bursting
53
What process causes the creation of different lymphocytes?
Haemotopeosis
54
Where can antibodies travel in the human body?
Anywhere in bodily fluid
| Except spinal cord & brain
55
What is the specificity of B lymphocytes?
Specific for epitope & antigen
Releases specific antibody
Multiple for each pathogen as many epitopes
56
How do B lymphocytes activate?
Interacts with antigen by B cell receptor
Endocytosis of antibody-antigen complex
Antigen presentation
T Helper interacts and stimulates mitosis of specific B cell
Plasma & B Memory produced
57
What is the process whereby T Helper cells cause the mitosis of specific cells?
Clonal selection
58
What is a plasma cell?
Cell that produces many antibodies
2000 antibodies / second
Only alive for a few days
59
What does a B memory cell do?
Doesn't produce antibodies
Can identify and cause secondary immune response
Survives for decades
60
What is the advantage of the secondary immune response?
Response is larger and faster
61
How do B memory cells cause the secondary immune response?
When activated, they divide rapidly and produce plasma cells
62
What organelles are required for plasma cells and why?
Mitochondria - energy for protein synthesis
Rough Endoplasmic reticulum - needed for protein synthesis
Golgi body - provides vesicles for exocytosis
63
What type of molecules are antibodies?
Glycoproteins synthesised by B cells
64
What is an antibody made up of?
4 polypeptide chains - 2x Heavy chain
| 2x Light chain
65
How do antibodies cause pathogen death?
Do not kill cells, enhances phagocytosis by
Viral neutralisation
Agglutination
Precipitation of soluble antigens
66
What is viral netralisation?
Blocks antigen binding sites
| Cannot bind to host
67
What is agglutination?
Forms clumps of the pathogen
68
What is precipitation of soluble antigens?
Antibodies bind to soluble antigens making them insoluble
69
What is formed when an antibody binds to an antigen?
An antigen-antibody complex
70
What are the two regions of antibodies?
Variable region
| Constant region
71
What are the binding sites of antibodies?
Antigen binding sites located in the variable region
72
What does the binding site consist of?
Sequence of amino acids, specific 3-D shape
| Binds to specific antigen epitope
73
What is HER2 and where is it found?
Receptor over-expressed on breast cancer cells
74
What is the treatment for breast cancer cells with over-expressed HER2?
HER2 antibody produced in lab (herceptin)
Neutralises growth receptor
Flags cell for destruction
75
What is an antibody-drug conjugate?
Many molecules of a drug bonded to the constant region of an antibody
76
How is using an antibody-drug conjugate advantageous?
Drug is more specific
77
What do the drugs in antibody-drug conjugates typically do to destroy the target cells?
Prevents microtubule formation in mitosis
78
What is the drug called in an antibody-drug conjugate?
Cytotoxic agent
79
What does the cytotoxic agent have to be in an antibody-drug conjugate?
Non-immunogenic (immune system won't destroy)
Non-toxic to self cells
Highly potent in small quantities
80
What does the Ab have to be in an antibody-drug conjugate?
Maintains characteristics
Targets well known antigen on target cell
Minimises non-specific binding
81
What is a linker?
The bond between the drug and the antibody in an antibody-drug conjugate
82
What is the properties of the linker?
Stable so the antibody-drug conjugate remains intact
| Ensures cytotoxic agent is functional
83
What does ELISA stand for?
Enzyme Linked Immunosorobant Assay
84
What is an assay?
Biochemical test
85
What are the two types of ELISA test?
Indirect ELISA - tests for antibodies (Ebola Ab)
| Sandwich/direct ELISA - tests for antigen (Insulin)
86
What is the process of a Sandwich/Direct ELISA?
Antibody bound to well
Sample added
Wash with distilled water to leave specific antigen
Secondary antibody with enzyme added
Washed & substrate added
Colour change caused by enzyme on secondary antibody
Colour measured
87
What is the process of a Indirect ELISA?
Antigen bound to well
Sample added
Washed with distilled water to leave specific Ab
Secondary antibody with enzyme attaches to 1st antibody
Washed & substrate added
Colour change caused by enzyme on secondary antibody
Colour measured
88
What is a monoclonal antibody production?
Antibodies which bind to a specific epitope
89
What is the process of monoclonal antibody production?
Inject specific antigen into mouse
Plasma cells stimulated & isolated from spleen
Cultured with myeloma cells induced in mouse (immortal)
Hybridoma cells formed (B cell, myeloma cell + polyethylene glycol)
Cells are separated & cloned under microscope
Harvest antibodies & humanised for human cells
90
What are the ethical issues of monoclonal antibody production?
Production involves use of mice, causing cancer in their cells. Reservations on animal testing
Deaths associated with treatments, risks & benefits so patient permission required
Testing caused near death of trial patients, concerns of conduct in drug trials
91
Why are myeloma cells used in antibody production?
Plasma cells only live for 3-4 days
| Myeloma cells are immortal
92
What type of response does vaccination cause?
Acquired --> Artificial --> Active
93
What does a vaccine contain?
Inactivated or attenuated pathogen/toxins
| Response against antigen caused
94
What does a vaccine cause?
Memory (T&B) cells produced
| Triggers primary immune response, boosters trigger secondary
95
Why are vaccines used?
Economically viable
Limited side affects
Ease to produce, store & transport
Potential to produce herd immunity
96
What is herd immunity?
Reduced transmission by high proportion of population being immune due to vaccination
Protects those who are not immunised
97
Who does herd immunity protect?
Those who are not immunised
| E.g babies/very young
98
When is herd immunity ineffective?
Patient develops illness following vaccination
Patient has defective immune system
Antigenic variability (mutation)
Pathogen species variability
Pathogens concealed inside cells/ outside body
Patient objects to vaccination
99
What are the ethical concerns of vaccines?
Development: use of animals, human trials, insufficiently tested
Side effects
Expense: spending money on this instead or something else
100
What is the pregnancy testing for?
Human chorionic gonadotrophin (hCG)
| Produced by women during fetal development
101
What is the process for pregnancy testing?
Free monoclonal antibodies specific to hCG are conjugated to enzyme on the reaction site
Fixed antibodies which traps hCG are found on the test site, and that which traps the free antibody at the control site
hCG binds to free antibodies and causes colour change at test site
Free antibodies cause colour change at control site
102
What does HIV stand for?
Human Immunodeficiency Virus
103
What does AIDS stand for?
Acquired Immune Deficiency Syndrome
104
What is AIDS?
A condition whereby the immune system deteriorates and fails
Makes them more vulnerable to other infections
Develops when T-helper cell numbers reach a critically low number, by HIV
105
What does HIV do to the body?
Infects & kills T-helper cells which are host cells
| Without T-helper cells it is difficult to mount an effective immune response
106
What is the structure of HIV?
Core than contains RNA and proteins (reverse transcriptase & intergrase)
Coating called a capsid (around core)
Outer layer called envelope made of membrane from host cell
Attachment proteins sticking out from envelope
107
What is an attachment protein?
Protein that attaches to a receptor molecule on the cell membrane on T-helper cell (CD4)
108
Why does HIV & other viruses need host cells to replicate?
They have no ribosomes or other organelles required for reproduction
109
What is the process of HIV replication?
Attachment protein attaches to receptor molecule on T-helper cell membrane
Capsid released into the cell, uncoats and releases contents
Reverse transcriptase converts ssRNA -> ssDNA -> dsDNA
Intergrase inserts viral DNA into the host DNA
Host cell makes viral proteins from viral DNA
Viral proteins assemble new viruses, which bud from the host and form new viral cells
110
What is the latency period?
Time whereby HIV replication drops to a lower level after initally diving rapidly
111
Why does HIV kill T-helper cells?
They undergo apoptosis
112
How long does HIV take to cause AIDS to develop?
10 years without treatment
113
What are the initial symptoms of AIDS?
Minor infection of mucous membranes & recurring respiratory infects
114
What are the mid-stage symptoms of AIDS?
Immune system cells decreases
| More susceptible to more serious infections
115
What are the late stage symptoms of AIDS?
Range of serious infections that can kill the patient
116
What drugs are used for HIV?
No cure/vaccine for HIV
| Antiviral drugs slow down the progression of HIV infection
117
What is the best way to control HIV infection?
Reducing the spread via unprotected sex, or from mother to fetus
118
How do antibiotics kill bacteria?
Interfering in their metabolic reactions by targeting their bacterial enzyme & ribosomes
119
Why can antibiotics not kill viruses?
They use human ribosomes & enzymes which antibiotics don't harm
120
What are antiviral drugs?
Drugs which target virus-specific enzymes
| E.g HIV has the enzyme reverse transcriptase
