Immunology C3 Flashcards
make sure to understand antigenic drift (extension)
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
person shows no symptom when infected by disease organism but can pass disease to another individual
4
Q
define disease reservoir
A
where pathogen is normally found
may be in humans or another animal and may be a source of infection
5
Q
define endemic
A
a disease always present at low levels in an area
6
Q
define epidemic
A
where there is significant increase in 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 against 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
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 same/very similar antigens on surface
such types are sub groups/strains of a microbial species which may be used to trace infections
usually identified by using antibodies from serum
14
Q
define antigen
A
molecule that causes immune system to produce antibodies against it
may be individual molecules or those on surface of cells
15
Q
define antibody
A
protein produced by immune cells (B cells) which binds to a specific antigen
16
Q
define disease
A
body acting as a host to other living organisms
17
Q
what does immunology concern?
A
immune system and how it protects body
studies an organisms response to invasion by foreign microbes and their products
18
Q
give examples of microbes that live on or in the body
A
fungi
protoctista
bacterial species
19
Q
what do these microbes do to the body in general?
A
cause disease in a parasitic relationship such as secreting toxins
20
Q
what is the plus side, however, of many of these microbes?
A
they contribute to our health and defend us against disease in a symbiotic or mutualistic relationship, e.g. escherichia coli in the large intestine synthesises vitamin K which is absorbed by the body
21
Q
how might E.coli benefit from humans?
A
the human body provides E.coli with a safe, comfortable and enclosed living environment in which the bacteria receives the required nutrients like sugars for reproduction and growth
22
Q
what can bacteria be infected by?
A
a DNA virus called bacteriophages
23
Q
what 5 diseases do we need to know about?
A
malaria
cholera
tuberculosis
influenza
smallpox
24
Q
what is the name of the pathogen of cholera?
A
vibrio cholerae
25
what is the type of pathogen of cholera?
gram-negative bacterium
26
where is the site of infection and the symptoms of cholera?
toxins affect the human gut lining, causing a watery diarrhoea, severe dehydration and frequently death
27
what is the mode of transmission of cholera?
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
28
how to prevent and control cholera?
treatment of wastewater, good hygiene and provision of clean drinking water
vaccine may provide temporary protection
29
what is the treatment of cholera?
antibiotic treatment is possible but oral rehydration is the main method of treatment
30
what is the name of the pathogen of TB?
mycobacterium tuberculosis
31
what is the type of pathogen of TB?
either gram-negative or positive bacterium
32
where is the site of infection and the symptoms of TB?
most commonly affect lung and neck lymph nodes
symptoms include coughing, chest pain and coughing up blood
33
what is the mode of transmission of TB?
can be spread rapidly in overcrowded conditions and is transmitted in airborne droplets through coughing and sneezing of infected individuals in close proximity
34
how to prevent and control TB?
BCG vaccination programme for children
35
how to treat TB?
a long course of anitibiotics
36
what is the name of the pathogen of small pox?
variola major
37
what is the type of pathogen of small pox?
virus
38
where is the site of infection and the symptoms of small pox?
small blood vessels of the skin, mouth, throat and lungs causing a rash and blisters
it has a 30% to 60% fatality rate
39
what is the mode of transmission of small pox?
airborne droplets of infected individuals in close proximity
it's eradicated outside labs
40
how to prevent and control small pox?
it is now extinct due to immunisation programs and was possible due to low rates of antigenic mutation/variation
in addition, there was no animal reservoir and people were keen to be immunised because of the devastating effects of the disease
41
what is the name of the pathogen of influenza?
influenza has three main subgroups, and each has many antigenic types
42
what is the type of pathogen of influenza?
virus
43
where is the site of infection and the symptoms of influenza?
upper respiratory tract, causing a sore throat, coughing and fever
44
what is the mode of transmission of influenza?
airborne droplets through coughing and sneezing of infected individuals in close proximity
45
how to prevent and control influenza?
quarantine and hygiene but it isn't easy to control
annual vaccination programs, but due to new types it is not always effective
46
what is the treatment of influenza?
antibiotics are ineffective against influenza and are only used to treat the symptoms of secondary bacterial infection
rest, keep warm, drink plenty of fluids and painkillers
47
what is the name of the pathogen of malaria?
plasmodium
48
what is the type of pathogen of malaria?
a protoctist
it has two main species with many antigenic types
49
where is the site of infection and the symptoms of malaria?
liver cells and red blood cells, causing them to burst when more parasites are produced (lysis)
symptoms include severe bouts of fever and flu-like illness, headache, muscle aches and tiredness. nausea, vomiting and diarrhoea may also occur
50
what is the mode of transmission of malaria?
by a vector- a female mosquito from the genus Anopheles when feeding on blood and it becomes endemic in sub-tropical regions
51
how to prevent and control malaria?
knowledge of life cycles, nets, clothing and repellant
vaccines are difficult to develop
drug treatment to reduce the chances of infection
52
what is the treatment of malaria?
drugs that affect plasmodium outside cells are available but limited success and has side effects
53
what is plasmodium?
a single-celled parasite
plasmodium = genus
54
when does the transmission of the parasite by the mosquito occur?
when the infected mosquito pierces the skin of a human to take a blood meal
55
why are only adult females vectors of the plasmodium parasite?
thy feed on human blood
it is the primary host and does not suffer from the presence of the parasites
56
why are male mosquitos not vectors of the plasmodium parasite?
males only feed on the nectar of plants to get sugar
57
describe the five stages of the plasmodium parasite life cycle in the human body
1 - the infected mosquito takes a blood meal, and the plasmodium parasite enters the bloodstream
2/3 - plasmodium then travels to and then invades liver cells where the parasite matures
4 - the liver cells rupture and release plasmodium parasites. then they invade red blood cells and multiply asexually. red blood cells also rupture, releasing more plasmodium parasites which invade other red blood cells
the rupture of red blood cells results in severe fever
5 - if a female mosquito feeds on an infected individual, the plasmodium parasites infect the mosquito, which acts as a vector to pass the disease onto another host
58
give five preventative measures for responding to mosquito behaviour
sleep under nets
nets are treated with the pyrethroid insecticide
spray indoor walls with insecticide
drain or cover stagnant water e.g. water tanks, ponds
film of oil on water
59
give the reasons for the five preventative measures for responding to mosquito behaviour
sleep under nets - mosquitos feed at night
nets treated with insecticide - pyrethroid kills mosquitos
spray indoor walls with insecticide - kills mosquitos as they rest on walls after feeding
drain/cover stagnant water - removes female mosquito's access to egg-laying sites
film of oil on water - prevents larvae from obtaining oxygen
60
give three preventative measures of biological control against mosquitos and the reasons why
introduce fish into water - fish eat the aquatic larvae
infect mosquitos with bacterium - bacteria infection blocks plasmodium development in the mosquito
male mosquitos sterilised with X-rays - no offspring would be produced if they mate with females
61
why have vaccines against malaria been proven difficult to develop?
the plasmodium parasite has high mutation rates, and there are many antigenic types
62
what are viruses described as when they are outside of a host cell and what does it mean?
being inert
essentially particles and have no metabolic pathways
63
where can they only replicate and what do they do to the host cell?
once they are inside a host cell where the enzyme machinery of that host cell is hijacked to make more viral copies
64
what two reproductive cycles can viruses be grouped to?
lysogenic and lytic
65
describe the lytic pathway
viruses immediately reproduce using the host's metabolism to copy their nucleic acid and synthesise new protein coat (capsid)
once new viral particles called virions have been assembled in the host cell cytoplasm, they will leave the host cell to infect new cells in two ways
66
what are the two ways viruses will leave the host cell?
lysis of the host cells e.g. common cold virus
budding from the host cell surface - when the virus becomes enclosed by part of the host cell membrane e.g. influenza virus
67
describe the lysogenic pathway
after the virus penetrates the host cell and sheds the capsid, the viral nucleic acid is integrated into the host cell genome and remains there for many cell generations/divisions with no clinical effect
then, the virus enters the lytic cycle ( due to stressful conditions where the phage DNA is excised from the bacterial chromosome), which is when symptoms are produced, e.g. Herpes simplex virus, HIV virus
68
what 4 ways can viruses be pathogenic and describe them?
cell lysis - when viruses escape from cells to infect other cells/organisms (shedding)
production of toxic substances
cell transformation - viral DNA can integrate into the host chromosome. if the DNA inserts into a proto-oncogene/tumour suppressor gene, in can result in the cell undergoing rapid and uncontrolled cell division i.e. becoming cancerous
immune suppression
69
(exam question) how are new HIV particles made?
viral DNA transcribes messenger RNA and new viral RNA
messenger RNA carries code for amino acids as triplets of bases/codons to ribosomes
viral protein is assembled
viral protein and viral RNA assembled into new virions/virus particles
70
define antibiotics
a substance produced by a fungus which diminishes the population growth of bacteria
71
what are the two modes of action of antibiotics and describe them?
1 - bacteriostatic - prevent population growth of bacteria
2 - bactericidal - kill bacteria
72
how can antibiotics treat bacterial infection without harming the patient?
they act on bacteria and not on eukaryotic cells/viruses
73
what are broad-spectrum antibiotics?
they act against a wide range of disease-causing bacteria by targeting both gram-positive and gram-negative bacterial groups
74
what are narrow-spectrum antibiotics?
they are active against a selected group of bacterial types
they can act on either gram-positive or gram-negative bacteria, but not both
75
describe the bacterial cell wall structure
contains peptidoglycan consisting of molecules of polysaccharide cross-linked by amino acid side chains, which provides strength and prevents osmotic lysis
in some bacteria, this cell wall is surrounded by an outer layer of lipopolysaccharides
the Gram stain reaction highlights cells with this additional layer (gram-negative), and they retain a counter stain and appear pink/red
the presence of this extra layer provides Gram-negative bacteria with protection from some antibacterial agents such as lysozyme and Penicillin
76
what type of antibiotic is tetracycline?
a broad-spectrum, bacteriostatic antibiotic
77
how does tetracycline work?
it affects protein synthesis
gram - and gram + bacteria carry out protein synthesis
tetracycline blocks the second tRNA binding site in the large subunit of bacterial ribosomes, preventing the binding of a tRNA molecule's anticodon to its complementary codon
therefore, amino acids won't join by peptide bonds, and translation is prevented
78
what type of antibiotic is Penicillin?
a narrow-spectrum, bactericidal antibiotic
79
how does Penicillin work?
affects the formation of cross-linkages in the peptidoglycan cell wall during growth and division of bacterial cells
it does this by binding to and inhibiting the enzyme transpeptidase which is responsible for the formation of these cross-linkages
penicillin binds irreversibly to transpeptidase, and it is not complementary to the active site of this enzyme, so the enzyme's function is permanently altered and the cell wall is weakened
80
what type of inhibitor is Penicillin?
non-competitive inhibitor as it has a shape that is not complementary to the active site and binding is irreversible
81
what effect will the weakened cell wall have as a result of penicillin on the bacteria?
the bacterial cell wall will gain water by osmosis and the cytoplasm will swell
eventually, the cell will lyse as the cell wall is not strong enough anymore
82
is gram-positive more susceptible to penicillin or gram-negative and explain why?
Gram-positive bacteria
due to their thick peptidoglycan cell wall
gram-negative bacteria only have a thin peptidoglycan cell wall and contain the outer lipopolysaccharide layer, so penicillin is less effective
83
why are viruses not affected by antibiotics?
they have no cell wall, ribosomes, or metabolic pathways to disrupt
84
what are two sources of antibiotic resistance alleles?
bacteria divide under optimum conditions and have a high mutation rate. naturally occurring mutations that confer resistance to antibiotics give these bacteria a selective advantage in the presence of antibiotics
plasmids contain the antibiotic resistance allele and it can be transferred from one bacterium to another via conjugation
85
what has overuse of bacteria caused?
in the accidental selection of bacterial strains that are completely unaffected by some antibiotics
86
when do bacteria have a selective advantage of having resistance to antibiotics?
when the antibiotic is present
so overuse only selects for resistant bacteria, and the frequency of the resistance allele increases
if there are no antibiotics in the environment, then bacteria with this resistance do not provide a selective advantage over bacteria that don't have resistance
87
give examples of clinically important bacteria that show antibiotic resistance and examples of those that are resistant to several antibiotics
bacteria that causes leprosy, TB and gonorrhoea
1- MRSA
2 - clostridium difficile
88
Give examples of 2 bacteria that are resistant to several antibiotics?
MRSA = methicillin-resistant Staphylococcus aureus
Clostridium difficile
89
What barriers and responses does the immune system have to resist disease and what must the immune system be able to distinguish?
Physical barriers
Of those fail then there are chemical and cellular responses
It must be able to detect foreign antigens and distinguish them from self antigens in its own tissues
90
Give examples of natural barriers and non-specific (passive) immune responses
Ciliated mucous membranes
Blood clotting
Localized inflammation
Tear ducts, saliva and stomach
Skin
Skin flora
Phagocytosis and antigen presenting cells
91
How does ciliated mucous membranes protect from disease and pathogens?
Inhaled air is a source of microorganisms
Mucus traps them and cilia on ciliated epithelial cells waft to bring the mucus up and out of the trachea
Cilia in the nose filter air and trap dust particles but no mucus is produced
92
How does blood clotting protect from disease and pathogens?
If capillaries are broken, blood prevent the entry of pathogens
93
How does localized inflammation protect against diseases and pathogens?
To localize breaks in the barrier e.g. skin
94
How does skin protect against diseases and pathogens?
A tough barrier and vitamin C is required to maintain strong connective tissue containing keratin and collagen
95
How does skin flora protect against diseases and pathogens?
Bacteria and fungi found on our skin offer competition for pathogenic bacteria
These natural flora don’t wash off the body as easily as pathogenic bacteria
96
How does tear ducts, saliva and the stomach protect from disease and pathogens?
Lysozyme in tears and saliva hydrolyse peptidoglycan cell walls to kill bacteria
Stomach acid kills many bacteria
97
How does phagocytosis and antigen presenting cells protect from diseases and pathogens?
A phagocyte engulfs a bacterium, enclosing it in a vacuole
Lysosomes fuse with this vacuole releasing hydrolytic enzymes that destroy the bacteria
These can then add the antigens to their own membrane becoming an antigen presenting cell supporting the specific immune response (antigens from the digested bacterium are presented on the cell surface, used by T-lymphocytes)
98
What does active immune response mean?
The body produced a specific response to a foreign antigen like lymphocytes
99
What are lymphocytes?
Subgroups of leucocytes (WBCs) that are produced from stem cells in the bone marrow
100
What are the two components of a specific immune response?
Humoral response
Cell mediated response
101
What happens in the humoral response?
B lymphocytes, originate from stem cells in the bone marrow and mature in the spleen and lymph nodes
Millions of different B cells circulate in the blood stream and lymph vessel and each has a specific receptor on its surface which bond to one type of antigen
When a foreign antigen enters the blood or lymph vessels, specific B lymphocytes bind to the foreign antigens. The B cells become activated stimulating clonal expansion (divide by mitosis)
Clonal expansion of B cells form:
- Plasma cells which secrete antibodies specific to the foreign antigen
- Memory B cells which remain dormant in the blood circulation ready to rapidly divide by clonal expansion to form more B lymphocytes of the same antigen is encountered in the future
102
describe antibodies
Y-shaped globular proteins, known as immunoglobulins and are often given the symbol Ig,
Each antibody is specific to the antigen to which they bind, forming an antigen-antibody complex
103
what happens when the antibody binds to the antigen?
they render the antigen inactive by a process called agglutination
this allows phagocytes to locate and engulf the pathogens
104
what is agglutination?
clumping together of bacteria
105
what can antibodies also bind to?
toxins
they undergo agglutination rendering them inactive
106
describe the tips of the Y structure
they are specific and complementary to a particular antigen
the antigen binding site
107
how many antigens can each antibody bind to?
two antigen molcules
108
what two regions are there in an antibody?
variable region (tips)
constant region
109
which part of the antibody is the light chain and which part is the heavy chain?
light chain - top half of the Y structure
heavy chain - bottom half of Y structure
110
where are disulphide bridges located in an antibody?
between light and heavy chains allowing them to open and close
111
what's the highest level of protein structure an antibody has?
quaternary
112
how is the structure of an antibody adapted to help agglutination occur?
there are two antigen-binding sites
113
what happens in the cell-mediated response?
T lymphocytes also originate from stem cells in the bone marrow but are activated in the thymus gland
when a phagocyte eg a macrophage, engulfs a pathogen, the pathogen is hydrolysed into component parts (lysosomes release hydrolytic enzymes to digest the pathogen)
the phagocyte can then present some of these parts on its membrane surface and becomes an antigen-presenting cell
other antigen-presenting cells are B lymphocytes and infected body cells
when a T lymphocyte detects a specific antigen on an antigen-presenting cell, it is stimulated to undergo clonal expansion
clonal expansion of T lymphocytes form:
- T helper cells produce chemicals called cytokines, which (1) stimulate more phagocytic cells to migrate to the infected tissue, which then engulfs more of the pathogens and digest them, and other lymphocytes are also stimulated; (2) stimulate clonal expansion of plasma B cells to make and secrete antibodies specific to that particular antigen
- 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
- Cytotoxic T killer cells destroy infected body cells that have specific antigens on their surface by lysing the cells, and they secrete chemicals such as hydrogen peroxide into infected cells
114
what happens in the primary immune response?
- on first exposure to the antigen, there is a latent period; phagocytes engulf the foreign antigen/cell/virus
- humoral and cell-mediated response is initiated
- antibodies are specific to the antigen and bind to it, holding the pathogen in place (agglutination)
- the B plasma cells secrete a low level of antibodies for about three weeks, after which the infection usually subsides
115
what happens 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
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, and no memory cells are produced
117
give 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 antibodies are injected into an individual eg tetanus antitoxin, rabies and small pox
118
describe active immunity
- the individual produces their own antibodies
- protection is long-lasting due to the production of antigen-specific memory cells (B and T)
119
give examples of active immunity
- natural production following infection
- artificial production following vaccination eg rubella, influenza and measles
120
describe antibody injections
- in an emergency, antibodies can be injected to provide rapid protection against a pathogen eg rabies
- this allows time for a person's immune system to develop an active immune response
- injections of antibodies are also used with people who do not develop a strong immune response to a vaccination or who have a weakened immune system
121
what four things can a vaccine be?
DNA vaccines
weak/live attenuated vaccines
subunit vaccines - antigens isolated from the pathogen
inactivated toxin or inactive/killed pathogen
122
how do vaccines work?
-often, a weakened/inactive form of the pathogen is injected into an individual
-specific antigens on the pathogen will be detected by specific B and T lymphocytes
-B and T cells will undergo clonal expansion, triggering an immune response
-the individual may show some symptoms as their body will undergo a normal immune response to the weakened pathogen
-as part of this response, memory cells will be produced
-if the same antigen is ever encountered in the future, memory cells will undergo rapid clonal expansion
-the pathogen will be destroyed before it can produce any symptoms so the person is said to be immune
123
what are the features of a successful vaccine?
- safe and has few side effects
- induces immunity and prevents the individual becoming unwell with the disease in the future
124
what kind of pathogens are more likely to be protected by a single round of immunisations?
ones that exhibit no or low levels of antigenic variation, e.g. rubella
125
what kind of pathogens are more difficult to protect against?
ones that have many antigenic types and mutate frequently, e.g influenza
protection against these organisms require repeated immunisation against the most common antigens, however even this isn't always effective
126
what type of individuals are offered flu vaccinations on the NHS?
older people, immunocompromised and people with asthma
127
how often are these individuals offered flu vaccinations and why?
annually because there are many antigenic types of influenza and new types are always occurring due to high mutation rates
annual vaccinations contain a few strains that are predicted to be the most prevalent that year
128
what is herd immunity?
if enough people in a population are vaccinated the spread of disease is controlled so even people who are not vaccinated have some protection
herd immunity relies on a certain proportion of the population being vaccinated; if the number of people vaccinated falls below a critical level, diseases may be able to spread
129
what are some ethical considerations for vaccination programmes?
-cost vs effectiveness of the vaccine
-side effects, whether real or perceived
-protection of the individual compared to the protection of the community
-the rights of the individual when considering mandatory compared to voluntary programmes
-religious objections
-mistrust of pharmaceutical companies
-safety fears
-some prefer natural/alternative medicine
130
describe human trials
when a new vaccine or drug is developed, it needs to be trialled to ensure it is safe and effective
the clinical trials involve first testing a new drug on a small number of healthy individuals to find out a safe dosage and look for side effects
The drug is then tested on a larger group of patients to see how well it works
131
what criteria should be used to select the participants for the clinical trial to ensure the results are valid?
age
ethnicities
sex
medical history
other medication
body compositions
large sample size
