immunology Flashcards
1
Q
define pathogen
A
an organism that causes a disease, damaging the host
2
Q
define infectious
A
a disease that may be passed or transmitted from one individual to another
3
Q
define carrier
A
a person who shows no symptoms when infected by a disease organism but can pass the disease to another individual
4
Q
define disease reservoir
A
where a pathogen is normally found, this may be in humans or another animal and may be a source of infection
5
Q
define endemic
A
a disease which is always present at low levels in an area
6
Q
define epidemic
A
where there is a significant increase in the usual number of cases of a disease often associated with rapid disease spread
7
Q
define pandemic
A
an epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people
8
Q
define vaccine
A
uses non-pathogenic forms, products or antigens of micro-organisms to stimulate an immune response which confers protection again subsequent infection through memory cells
9
Q
define antibiotics
A
substances produced by microorganisms which affect the growth of bacteria
10
Q
define antibiotic resistance
A
where a microorganism which should be affected by an antibiotic is no longer susceptible to it
11
Q
define vector
A
a living organism which transfers a disease from one individual to another
12
Q
define toxin
A
a chemical produced by a pathogen which causes damage to cells and tissues of the host
13
Q
define antigenic types
A
organisms with the same or very similar antigens on the surface
- such types are sub groups or strains of a microbial species which may be used to trace infections.
- they are usually identified by using antibodies from serum
14
Q
define antigen
A
a molecule that causes the immune system to produce antibodies against it
- these may be individual molecules or those on the surface of cells
15
Q
define antibody
A
a protein produced by immune cells (B cells) which binds to a specific antigen
16
Q
what is immunology?
A
immunology concerns the immune system and how it protects the body.
- studies an organisms response to invasion by foreign microbes and their products
17
Q
what is a disease?
A
the body acting as a host to other living organisms
18
Q
how might E coli benefit from humans?
A
the human body provides E-coli with a safe, enclosed and comfortable living environment in which the bacteria receive the required nutrients (sugars) for reproduction and growth
19
Q
what is the name and type of cholera?
A
NAME: vibrio cholerae
TYPE: gram negative bacterium
20
Q
what is the site of infection and symptoms of cholera?
A
toxins affect the human gut lining causing a watery diarrhoea, severe dehydration and frequently death
21
Q
what is the mode of transmission of cholera?
A
humans act as reservoirs or carriers and can contaminate water supplies with the pathogen
- the pathogen is transmitted by drinking contaminated water, although it only multiplies in the human host
22
Q
how is cholera prevented and controlled?
A
- treatment of waste water
- good hygiene
- provision of clean drinking water
- vaccine (killed organism or possibly genetically engineered) may provide temporary protection
23
Q
what is the treatment for cholera?
A
antibiotic treatment is possible but oral rehydration is the main method of treatment
24
Q
what is the name and type of pathogen for tuberculosis?
A
NAME: mycobacterium tuberculosis
TYPE: bacterium
25
what is the site of infection and symptoms for tuberculosis?
- most commonly affects lung and neck lymph nodes
- symptoms include: coughing, chest pain and coughing up blood
26
what is the mode of transmission for tuberculosis?
- can be spread rapidly in overcrowded conditions
- transmitted in airborne droplets through coughing and sneezing of infected individuals in close proximity
27
how is tuberculosis prevented and controlled?
- BCG vaccination programme for children
28
what is the treatment for tuberculosis?
a long course of antibiotics
29
what is the name and type of smallpox?
NAME: variola major
TYPE: virus
30
what is the site of infection and symptoms for smallpox?
- small blood vessels of the skin, mouth, throat and lungs, causing a rash and blisters
- 30 to 60% fatality rate
31
what is the mode of transmission for smallpox?
airborne droplets of infected individuals in close proximity
32
how is smallpox prevented and controlled?
- now extinct due to immunisation programme. this was possible due to low rate of antigenic variation / mutation
- in addition, there was no animal reservoir and people were keen to be immunised because of the devastating effects of the disease
33
what is the name and type of pathogen for influenza?
NAME : 3 main subgroups e.g H1N1
TYPE : virus
34
what is the site of infection and symptoms for influenza?
upper respiratory tract, causing:
- sore throat
- coughing
- fever
35
what is the mode of transmission for influenza?
airborne droplets through coughing and sneezing of infected individuals in close proximity
36
how is influenza prevented and controlled?
- quarantine and hygiene but difficult to control
- annual vaccination programmes, but due to new types this is not always effective
37
what is the treatment for influenza?
- antibiotics are ineffective against influenza and are only used to treat the symptoms of secondary bacterial infection
- rest, keep warm, drink water and take painkillers
38
what is the name and type of pathogen for malaria?
NAME : plasmodium spp.
TYPE : protoctistan
39
what is the site of infection and symptoms for malaria?
- liver cells and red blood cells, causing them to burst when more parasites are produced
symptoms:
- severe bouts of fever and flu-like illness
- headache
- muscle aches
- tiredness
- nausea
- vomiting
- diarrhoea may also occur
40
how is malaria prevented and controlled?
- knowledge of life cycles. nets, clothing & repellent
- vaccines difficult to develop
- drug treatment to reduce the chances of infection
41
what is the treatment for malaria?
drug that affect plasmodium outside cells are available but limited success and have side effects
42
how does transmission of malaria occur?
when the infected mosquito pierces the skin of a human to take a blood meal.
43
why are male mosquitos not vectors of the Plasmodium parasite?
- male mosquitos feed on the nectar of plants to get sugar
- they do not feed off blood like females
44
what is the primary and secondary host of malaria and describe.
primary host : adult female mosquito
- does not suffer from presence of parasites
secondary host : humans
- do show symptoms of infection
45
outline the life cycle of malaria
1. the infected mosquito takes a blood meal and the plasmodium parasite enters the bloodstream
2. plasmodium travels to and then invades liver cells, where the parasite matures
3. liver cells rupture and release plasmodium parasites. they then invade red blood cells and multiply asexually. red blood cells then also rupture, releasing more plasmodium parasites, which invade other red blood cells. the rupture of red blood cells results in severe fever.
4. if a female mosquito feeds on the blood of an infected individual, the Plasmodium parasites infect the mosquito, which acts as a vector to pass the disease onto another host
46
name preventative measures in relation to responding to mosquito behaviour
- sleep under nets
- nets are treated with the pyrethroid insecticide
- spray indoor walls with insecticide
- drain or cover stagnant water
- film of oil on the water
47
name preventative measures in relation to responding to biological control
- fish introduced into water
- infecting mosquitos with bacterium
- male mosquitos sterilised with x-rays
48
give a reason for sleeping under nets
mosquitos feed at night
49
give a reason for why nets are treated with the pyrethroid insecticide
pyrethroid kills mosquitos
50
give a reason for spraying indoor walls with insecticide
kills mosquitos as they rest on walls after feeding
51
give a reason for draining or covering stagnant water
removes female mosquitos access for egg-laying sites
52
give a reason for filming of oil on water
prevents larvae piercing surface for oxygen
53
give a reason for fish being introduced into water
larvae are aquatic and fish eat them
54
give a reason for infecting mosquitos with bacterium
bacteria infection blocks plasmodium development in the mosquito
55
give a reason for male mosquito being sterilised with x-rays
after they mate with females, no offspring are produced
56
why have vaccines for malaria proved difficult to develop?
the plasmodium parasite has high mutation rates and there are many antigenic types
57
what does inert mean, regarding viruses?
viruses outside the host cells
58
how many types of reproduction cycle for viruses?
what are they?
TWO TYPES:
- lysogenic cycle
- lytic cycle
59
describe what occurs in the lytic cycle
- viruses immediately reproduce using the host's metabolism to copy their nucleic acid and synthesise new coat protein
- once new viral particles have been assembled in the host cell cytoplasm, they will then leave the host cell
60
in what way do the virions leave the host cell cytoplasm?
- lysis of the host cell e.g common cold virus
- budding from the host cell surface (virus becomes enclosed by part of the host cell membrane) e.g influenza virus
61
describe what occurs in the lysogenic cycle
- following penetration of the host cell and shedding of the capsid, the viral nucleic acid is integrated into the host cell genome
- this may remain there for many cell generations with NO EFFECT
- the virus may then enter the lytic cycle at some later time, when symptoms are produced
62
list how viruses can be pathogenic?
- cell lysis
- production of toxic substances
- cell transformation
- immune supression
63
describe how cell transformation as a means of viruses being pathogenic
viral DNA can integrate into host chromosome
- if the DNA inserts into a proto-oncogene or tumour suppressor gene it can result in the cell undergoing rapid and uncontrolled cell division i.e becoming cancerous
64
describe how new HIV particles are made after they enter the host cell
(4 marks)
- viral DNA transcribes messenger RNA (mRNA) and new viral RNA
- messenger RNA carried code for amino acids as triplets / codons to ribosomes
- viral protein assembled
- viral protein and viral RNA assembled into new viriones
65
define antibiotic
a substance produced by a fungus which diminishes the population growth of bacteria
66
what are the 2 modes of action for antibiotics.
describe them and give examples
1. BACTERIOSTATIC - prevent population growth of bacteria e.g tetracyclin
2. BACTERICIDAL - kill bacteria e.g penicillin
67
describe broad-spectrum antibiotics
act against a wide range of disease-causing bacteria by targeting both gram positive and gram negative bacterial groups
68
describe narrow spectrum antibiotics
active against a selected group of bacterial types
- they can act on either gram positive or gram negative but not both
69
outline the structure of bacterial cell wall
- contains peptidoglycan consisting of molecules of polysaccharide cross-linked by amino acid side chains. this provides strength and prevents osmotic lysis
- in some bacteria this cell wall is surrounded by an outer layer of lipopolysaccharides
70
how are gram negative and gram positive bacteria identified?
- the gram statin reaction highlights cells with the addition layer in gram negative and they retain a counter stain and appear red
- this layer gives protection from some antibacterial agents such a lysozyme and penicillin
71
describe tetracycline
an antibiotic that affects protein synthesis, a metabolic process common to all bacteria
this means it is effective against a broader range of baceria, including gram +ve and some gram-ve species
72
how does tetracycline affect protein synthesis?
acts as a competitive inhibitor preventing codon-anticodon complexes forming at the second anti-codon binding site on the smaller subunit of bacterial ribosomes
- prevents the binding of a tRNA molecule to its complementary codon
73
what effect does the prevention of the binding of a tRNA molecule to its complementary codon?
adjacent amino acids won't join by peptide bonds and translation and protein synthesis is prevented
74
what does penicillin affect?
- affects the formation of cross-linkages in the peptidoglycan cell wall during growth and division of bacterial cells
75
how does penicillin affect the formation of cross linkages in the cell wall?
- by binding to and inhibiting the enzymes (transpeptidase) responsible for the formation of these cross linkages.
- binds irreversibly to transpeptidase and it is not complementary to the active site of the enzyme
76
explain what type of inhibitor penicillin is.
penicillin is a non competitive inhibitor, as binding is irreversible.
- penicillin has a shape that is not complementary to the active site
77
as a result of the penicillin the cell wall is weakened.
what effect would this have if the cells were placed in a hypotonic solution?
water will enter in by osmosis, the cell becomes turgid and eventually lysis occurs at
78
why are viruses not affected by antibiotics?
viruses have no cell wall or metabolic pathway to disrupt
79
why are gram positive bacteria more susceptible to penicillin?
due to their thick peptidoglycan cell wall
80
what are the two sources of antibiotic resistance alleles?
1. bacteria divide under optimum conditions and have a high mutation rate. naturally occurring mutations that confer resistance to antibiotics have given these bacteria a selective advantage in the presence of antibiotics
2. plasmids containing the antibiotic resistance allele can be transferred from one bacterium to another via conjugation
81
what is the passive immune response?
enables the body to resist disease.
82
what does the passive immune response allow the body to do?
able to detect foreign antigens and distinguish them from self antigens in its own tissues
83
name some natural barriers in the body
- ciliated mucous membranes
- blood clotting
- tear ducts, saliva
- stomach
- phagocytosis
- skin flora
- skin
84
describe ciliated mucous membranes as a natural barrier
mucus traps inhaled pathogens and cilia waft the mucus up and out of the trachea
85
describe blood clotting as a natural barrier
prevents the entry of pathogens through broken capillaries
86
describe tear ducts and saliva as a natural barrier
lysozyme
hydrolyses cell walls to kill bacteria
87
describe the stomach as a natural barrier
stomach acid kills bacteria
88
describe the skin as a natural barrier
covers the external surface of body
89
describe phagocytosis as a natural barrier
a macrophage (phagocytosis) engulfs bacteria into vacuoles, which fuse with lysosomes which release hydrolytic enzymes into the vacuole
90
describe skin flora as a natural barrier
commensal microorganisms on our skin compete with pathogenic bacteria
- the natural flora doesn't wash off the body as easily as pathogenic bacteria
91
what is the specific immune response?
what provides this?
in the adaptive immune response, the body produces a specific response to a foreign antigen
- lymphocytes provide this response
92
what are lymphocytes?
a type of leucocyte (white blood cell)
93
what are the two components to the adaptive immune response?
- the humoral response
- cell mediated response
94
where do B lymphocytes originate from and where do they mature?
originate from = stem cells in the bone marrow
mature = spleen and lymph nodes
95
describe the humoral response
- B cells circulate in the blood stream and lymph vessel. each has a specific receptor on its surface which bind to one type of antigen
- when a foreign antigen enters the blood or lymph vessels, specific B lymphocytes bind to the foreign antigens.
- this causes B cells to activate which stimulates clonal expansion
96
what does clonal expansion of B cells form?
- plasma cells
- memory B cells
97
what do plasma cells do?
secrete antibodies specific to the foreign antigen
98
what do memory B cells do?
remain dormant in the blood circulation ready to rapidly divide by clonal expansion to form more B lymphocytes if the same antigen is encountered in the future
99
what are antibodies?
Y shaped globular proteins (immunoglobulins)
- made from four polypeptides and has two antigen binding sites
100
what is the highest level of protein structure an antibody has?
quaternary
101
what type of bond (covalent) holds the polypeptide chains together between sulphur containing variable groups?
disulphide bridges
102
explain how the structure of an antibody ensures it only binds to one type of antigen?
complementary
103
In agglutination microbes are clumped together. This allows them to be destroyed more efficiently.
How is the structure of an antibody adapted to help agglutination occur?
there are 2 binding sites so the antibody can bind to two antigens at once
104
what is formed when the specific antibody binds to the antigen?
antigen-antibody complex
105
what does agglutination prevents?
prevents antigens infecting cells/producing toxins and allows phagocytic cells to engulf them in phagocytosis
106
where do T-lymphocytes originate from?
where are they activated?
originate - stem cells in bone marrow
activated - thymus gland
107
how are antigen presenting cells formed?
- when macrophages engulf a pathogen, the pathogen is hydrolysed into component parts
- the macrophage can then present some of these parts (antigens) on its membrane surface
- it is now an antigen presenting cell
108
what are some other cells that can present antigens on their surfaces?
- B lymphocytes
- infected body cells
109
what stimulates a T lymphocyte to go under clonal expansion?
when a T lymphocyte detects a specific antigen on an antigen presenting cell
110
how many different types of cells are made when T lymphocytes undergo clonal expansion?
what are they?
THREE
1. T helper cells
2. T memory cells
3. Cytotoxic T cell (killer cells)
111
describe T helper cells
produce chemicals called cytokines
cytokines:
- stimulate more phagocytic cells to migrate to the infected tissue, which then engulf more pathogens
- stimulate clonal expansion of plasma B cells to make and secrete antibodies specific to that particulate antigen
- (attracts T killer cells)
112
describe T memory cells
remain dormant in the circulation and then divide rapidly by clonal expansion to form more T lymphocytes if the same antigen is encountered in the future
113
describe cytotoxic T cell (killer)
destroy infected body cells (that have specific antigens on their surface) by LYSING the cells
e.g a normal body cell infected by a virus
114
explain why the latency period is much shorter and the antibody production much greater in the secondary immune response
- on re-exposure to the same antigen, after a very short latent period, memory cells undergo rapid clonal expansion
- a small amount of antigen stimulates rapid production of plasma B cells
- antibodies are made much more quickly and more concentrated than in the primary response
- the antibodies remain at high concentrations for longer and no symptoms develop
115
outline the steps in primary immune response
1. antigen-presenting cells engulf pathogens and display antigens
2. these antigen presenting cells activate specific T cells which undergo clonal expansion to form T helper cells which release cytokines
3. cytokines stimulate B cells to undergo clonal expansion forming B plasma cells which secrete antibodies against the antigen. memory cells produced
4. B lymphocyte with a specific receptor can also bind to an antigen on the pathogen and is stimulated to undergo clonal expansion
5. antibodies are specific to antigen and bind to it, holding the pathogen in place
6. the B plasma cells secrete a low levels of antibodies for about 3 weeks, after which the infection usually subsides
116
describe passive immunity
the body may receive antibodies that have been produced by another individual
- protection is short lived because the antibodies are recognised as non-self and are destroyed so no memory cells are produced
117
name examples of passive immunity
- when antibodies are transferred to the foetus via the placenta, or to the baby in breast milk
- artificial when pre-synthesised antibody is injected into an individual
118
describe active immunity
the individual produced their own antibodies
- protection is long-lasting due to production of antigen-specific memory cells
119
name some examples of active immunity
- natural production following infection
- artificial production following vaccination e.g against Rubella
120
why are antibody injections used?
- provide rapid protection against a pathogen
- used with people who do not develop a strong immune response to a vaccination or who have a weakened immune system
