communicable diseases Flashcards
1
Q
What are communicable diseases?
A
Diseases that can be passed from one organism to another, of the same or different species • Caused by infective organisms known as pathogens
2
Q
What are pathogens?
A
Microorganisms that cause disease
• Bacteria, viruses, fungi, and
protoctista
3
Q
What are vectors?
A
A living or non-living factor that transmits a pathogen from one organism to another, e.g. malaria mosquito • Common vectors include water and insects
4
Q
Describe bacteria
A
• Prokaryotes, so have no membrane-bound nucleus or organelles Classified in two main ways • By basic shapes: bacilli, cocci, vibrios, spirilla, spirochaetes • By their cell walls: the two main types of cell walls have different structures and react differently with gram staining • Gram positive bacteria look purple-blue e.g. MRSA • Gram negative bacteria appear red e.g. E.coli
5
Q
What are antibiotics?
A
A chemical or compound that kills or
inhibits the growth of bacteria
• The type of cell wall of the bacteria
reactive to different antibiotics
6
Q
What are viruses?
A
• Non-living infectious ages • 0.02-0.3 μm in diameter, so 50x smaller than the average bacterium • Considered by many scientists to be the ultimate parasite
7
Q
Describe viruses
A
• Basic structure is genetic material (DNA or RNA) surrounded by protein • Invade living cells where the genetic material of the virus takes over the biochemistry of the host cell to make more virsuses • All natural viruses are pathogenic - they cause disease in every other type of organism
8
Q
What are bacteriophages?
A
Viruses that attack bacteria • Take over the bacteria cells and use them to replicate, destroying the bacteria at the same time • Can be used to identify and treat some disease, and are very important in scientific research
9
Q
What are protoctista?
A
A group of eukaryotic organisms with a wide variety of feeding methods. Include single-celled organisms and cells group colonies • A small percentage of protoctista act as pathogens, causing diseases in both plants and animals
10
Q
Describe the protists that cause disease
A
They are parasitic - they use people or animals as their host organism • Pathogenic protists may need a vector to transfer them to their hosts e.g. malaria and sleeping sickness • May enter the body directly through polluted water e.g. amoebic dysentery and Giardia
11
Q
What are fungi?
A
Eukaryotic organisms that are often multicellular, although yeasts which cause human diseases e.g. thrush are single-celled • Cannot photosynthesise and digest their food extracellularly before absorbing nutrients • Many are saprophytes (feed on dead and decaying matter) • Some are parasitic (feeding on living plants and animals)
12
Q
Describe the fungi that cause disease
A
Fungal diseases are not a major problem in animals, but they can cause devastation in plants • Pathogenic fungi which cause communicable diseases are parasitic • They often affect the leaves of plants, stopping them photosynthesising, which quickly kills the plant • When fungi reproduce, they produce millions of spore which can spread huge distances, allowing them spread rapidly and widely through crop plants
13
Q
What is the mode of action of viruses?
A
Damaging the host tissues directly • Viruses take over the cell metabolism; the viral genetic material gets into the host cell and is inserted into the host DNA. The host cell is used to make new viruses which the burst out of the cell, destroying it, and then spread to infect other cells
14
Q
What is the mode of action of protoctista?
A
Damaging the host tissues directly • Take over cells and break them open as the new generation emerge, but don’t take over the genetic material of the cell • Digest and use the cell contents as they reproduce e.g. protoctists which cause malaria
15
Q
What are the modes of action of fungi?
A
Damaging the host tissues directly, and producing toxins which damage host tissues • Digest living cells and destroy them • This combined with the response of the body to the damage caused by the fungus gives the symptoms of disease • Some fungi also produce toxins which affect the host cells and cause disease
16
Q
What is the mode of action of bacteria?
A
Producing toxins which damage host tissues • Some bacterial toxins damage the host cell by breaking down the cell membranes • Some damage or inactivate enzymes • Some interfere with the host cell genetic material so that the cells cannot divide • These toxins are a by-product of the normal functioning of the bacteria
17
Q
List some examples of plant diseases
A
- Ring rot (bacterial)
- Tobacco mosaic virus (TMV)
- Potato blight (protoctist)
- Black Sigatoka (fungal)
18
Q
Describe ring rot
A
• Bacterial disease of potatoes, tomatoes and aubergines • Caused by the gram positive bacterium Clavibacter michiganesis • Damages leaves, tubers and fruit • Can destroy 80% of the crop and there’s no cure • Once infected, field can’t be used to grow potatoes again for 2 years
19
Q
Describe Tobacco Mosaic Virus (TMV)
A
Virus that infects tobacco plants, tomatoes, peppers, cucumbers, petunias, and delphiniums • Damages leaves, flowers and fruit, stunting growth and reducing yields • Resistant crop strains are available but there is no cure
20
Q
Describe potato blight
A
• Also tomato blight, late blight • Caused by the fungus-like protoctist oomycete Phytophthora infestans • Hyphae penetrate host cells, destroying leaves, tubes and fruit • No cure but resistant strains, careful management and chemical treatments can reduce infection risk
21
Q
Describe Black Sigatoka
A
Banana disease caused by the fungus Mycosphaerella fijiensis, which attacks and destroys leaves • They hyphae penetrate and digest the cells, turning the leaves black • No cure, but resistant strains are being developed, and good husbandry and fungicide can control the spread of the disease
22
Q
List some examples of animal diseases
A
- Tuberculosis (TB)
- Bacterial meningitis
- HIV/AIDS
- Influenza (flu)
- Malaria
- Ring worm
- Athlete’s foot
23
Q
Describe Tuberculosis (TB)
A
• Bacterial disease • Humans, cows, pigs, badgers and deer • Caused by; Mycobacterium tuberculosis and M. bovis • Damages and destroys lung tissue and suppress the immune system • Curable by antibiotics, and preventable by improving living standards and vaccination
24
Q
Describe Bacterial Meningitis
A
• Bacterial infection of the meninges of the brain • Can spread to the rest of the body causing septicaemia (blood poisoning) and rapid death • Many affects very young children and teenagers • Symptoms: blotchy red/purple rash that doesn’t disappear when a glass is pressed against it • Antibiotics cure it if delivered early • Vaccines protect against some forms of it
25
Describe HIV/AIDS
```
• AIDS (acquired immunodeficiency
syndrome) is caused by HIV
(human immunodeficiency virus)
• Targets T helper cell in the immune
system of the body
• Gradually destroys the immune
system, so affect people of open
to other infections e.g. TB,
pneumonia, and some types of
cancer
• Affects humans and some nonhuman
primates
• HIV is a retrovirus with RNA as its
genetic material
• Contains the enzyme reverse
transcriptase, which transcribes
the RNA to a single strand of DNA
to produce a single strand of DNA
in the host cell
• This DNA interacts with the
genetic material of the host cell
• The virus is assed from one person
to another in bodily fluids e.g.
unprotected sex, shared needles,
contaminated blood products, and
from mother to child during
pregnancy
• No vaccine and no cure, by antiretroviral
dress slow the progress
of the disease
```
26
Describe Influenza (flu)
```
• Viral infection
• Kills the ciliated epithelial cells in
the gas exchange system, leaving
the airways open to secondary
infection
• Can be fatal to young children, old
people, and people with chronic
illnesses
• Many of the deaths are from
severe secondary bacterial
infection on top of the original viral
infections e.g. pneumonia
• Affects mammals including
humans, pigs, birds (inc. chickens)
• 3 Strains (A,B,C); A are the most
virulent
• Flu viruses mutate regularly
• Vulnerable groups are given a
vaccine annually to protect against
changing strains
• No cure
```
27
Describe Ring Worm
```
• Fungal disease
• Mammals including cattle, dogs,
cats and humans
• Different fungi affect different
species
• Causes grey-white, crusty,
infectious circular areas of skin
• Not damaging, but looks unsightly
and may be itchy
• Anti fungal creams are an effective
cure
```
28
Describe Athlete’s Foot
```
• Human fungal disease
• Caused by Tinia pedia, a form of
human ring worm that grows on
and digests the warm, moist skin
between the toes
• Causes cracking and scaling,
which is itchy and may become
sore
• Anti fungal creams are an effective
cure
```
29
Describe Malaria
```
• Caused by the protoctista
Plasmodium, and spread by the
bites of infected Anopheles
mosquitoes
• Plasmodium parasite has a
complex life cycle with two hosts -
mosquitoes and people
• Reproduce inside the female
mosquito
• The female needs to take two
blood meals to provide her with
protein before she lays her eggs -
this is when Plasmodium is
passed onto people
• Invades red blood cells, liver and
brain
• No vaccine, limited cures
• Killing the mosquito through
insecticides
• Removing standing water,
mosquito nets, wind and door
screen, long sleeved clothing etc
```
30
What is direct transmission (animals)?
```
When a pathogen is transferred
directly from one individual to
another by:
• Direct contact (contagious
diseases)
• Inoculation
• Ingestion
```
31
Give details of the methods of direct transmission
```
Direct contact (contagious
diseases):
• Kissing or any contact with the
body fluids of another person e.g.
bacterial meningitis and many
STDs
• Direct skin-to-skin contact, e.g.
ring worm, athlete’s foot
• Microorganisms from faeces
transmitted not the hands, e.g.
diarrhoea diseases
Inoculation
• Through a break in the skin, e.g.
during sex (HIV/AIDS)
• From an animal bite (e.g. rabies)
• Through a puncture wound on
through sharing needles, e.g.
septicaemia
Ingestion
• Taking in contaminated food or
drink, or transferring pathogens to
the mouth from the hands, e.g.
amoebic dysentery, diarrhoeal
diseases
```
32
What is indirect transmission (animals)?
```
Where the pathogen travels from
one individual to another indirectly
• Fomites
• Droplet infection (inhalation)
• Vectors
• Transmission between animals and
humans
```
33
Give details of the methods of indirect transmission
```
Fomites:
• Inanimate object e.g. bedding,
socks or cosmetics, can transfer
pathogens such as athlete’s foot,
gas gangrene, and
Staphylococcus infections
Droplet infection(inhalation):
• Minute droplets of saliva and
mucus expelled from the mouth as
you talk, cough or sneeze
• If droplets contain pathogens,
when healthy individuals breathe
them in, they may become
infected e.g. TB, influenza
Vectors:
• Transmit communicable
pathogens between hosts
• e.g. mosquitoes transmit malaria,
rat fleas transmit bubonic plague,
dogs, foxes and bats transmit
rabies
Between animals and humans
• e.g. Bird flu strain H1N1, and
brucellosis (sheep to people)
• Minimising close contact with
animals and washing hands
• Vice versa e.g. foot-and-mouth
disease
```
34
What are the factors affecting
the transmission of
communicable diseases in
animals?
```
Overcrowded living and working
conditions
• Poor nutrition
• Compromised immune system,
e.g. having HIV/AID, or needing
immunosuppressant drugs after
transplant surgery
• (in humans) Poor disposal of
waste, providing breeding sites for
vectors
• Climate change - can introduce
new vectors and diseases, e.g.
increased temperatures promote
the spread of malaria
• Culture and infrastructure - in
many countries, traditional medical
practises can increase
transmission
• Socioeconomic factors - e.g. lack
of trained health workers and
insufficient public waning when
there is an outbreak of disease
```
35
What is direct transmission in plants?
The direct contact of a healthy plant
with any part of a diseased plant
e.g. TMV, tomato and potato blight,
and black Sigatoka
36
What are the types of indirect transmission in plants?
* Soil contamination
| * Vectors
37
Describe soil contamination
```
Infected plants often leave
pathogens (bacteria or viruses), or
reproductive spores from
protoctista or fungi in the soil
• Theses can infect the next crop
• e.g. black Sigatoka spores, ring rot
bacteria, spores of P. infestans,
and TMV
• Some pathogens (often as spores)
can survive the composting
process, so the infection cycle can
be completed when contaminated
compost is used
```
38
Describe vectors in plants
```
Wind
• Bacteria, viruses and fungal or
oomycete spores my be carried on
in the wind
• e.g. Black Sigatoka blown
between Caribbean islands, P.
Infestans sporangia form spores,
which are carried by the wind to
other potato crops/ tomato plants
Water
• Spores swim in the surface film
water on leaves
• Raindrop splashes carry
pathogens and spores etc
• e.g. spores of P. infestans (potato
blight) which swim over films of
water on leaves
Animals
• Insects and birds carry pathogens
and spores from one plant to
another as they feed
• Insects such as aphids inoculate
pathogens directly into plant
tissues
Humans
• Pathogens and spores are
transmitted by hands, clothing,
fomites, farming practices and by
transporting plants and crops
around the world
• e.g. TMV survives for years in
tobacco products
• Ring rot survive on farm
machinery, potato sacks etc.
```
39
What are the factors affecting
the transmission of
communicable diseases in
plants?
```
• Planting varieties of crops that are
susceptible to disease
• Over-crowding increases the
likelihood of contact
• Poor mineral nutrition reduces
resistance of plants
• Damp, warm conditions increase
the survival and spread of
pathogens and spores
• Climate change - increased rainfall
and wind promote the spread of
diseases; changing conditions
allow animal vectors to spread to
new areas; drier conditions may
reduce the spread of disease
```
40
Give basic ways in which plants defend themselves
| against pathogens
Waxy cuticle of leaves, bark on trees
and cellulose cell walls of individual
cells all act as barriers preventing
pathogens from getting in
41
What is the difference between plant and animal responses to diseased tissue?
```
Unlike animals, plants don’t heal
diseased tissue - they seal it off and
sacrifice it
• Because they are continually
growing at the meristems, they
can then replace the damaged
parts
```
42
How do plants recognise an attack?
```
1. Receptors in the cells respond
rapidly to pathogen attacks
2. Receptors in the cells respond to
molecules from the pathogens,
or to chemicals produced when
the plant cell wall is attacked
3. This stimulates the release of
signalling molecules that appear
to switch on genes in the
nucleus
4. This triggers cellular responses
including:
• Producing defensive chemicals
• Sending alarm signals to
unaffected cells to trigger their
defences
• Physically strengthening the cell
walls
```
43
What is callose?
```
A polysaccharide containing ß 1-3
linkages and ß 1-6 linkages between
the glucose monomers that is
important in the plant response to
infection
```
44
What role does callose play in plant physical defences?
```
Callose papillae:
• Within minutes of an initial attack
callose is synthesised and
deposited between the cell walls
an cell membrane in the cells
adjacent to infected cells
• These act as barriers, preventing
the pathogens entering the plant
cells around the site of infection
• Large amounts of callose continue
to be deposited in cell walls after
the initial infection. Lignin is
added, making the mechanical
barrier to invasion even thicker
and stronger
• Callose blocks sieve plates in the
phloem, sealing off the infected
part and preventing the spread of
pathogens
• Callose is deposited in the
plasmodesmata between infected
cells and their neighbours, sealing
them off from the healthy cells and
helping to prevent the pathogen
spreading
```
45
What happens in xylose formation?
```
This is when the xylem is blocked
from carrying water by a terpenefilled
swelling called a xylose. This
prevents pathogens moving through
the xylem
```
46
Give examples of plant chemical defences
```
• Insect repellents e.g. pine resin
and citronella from lemon grass
• Insecticides e.g. pyrethrins (made
by chrysanthemums and act as
insect neurotoxins) and caffeine
(toxic to insects and fungi)
• Antibacterial compounds including
antibiotics
• Antifungal compounds
• Anti-oomycetes e.g. glucanases
(enzymes made by some plants
that break down glucans;
polymers found in the cell walls of
oomycetes e.g. P. infestans)
• General toxins - some plants
make chemicals that can be
broken down to form cyanide
compounds when the plant is
attacked
```
47
Describe the antibacterial compounds made by plants
```
• e.g. phenols - antiseptics made in
many different plants
• Antibacterial gossypol produced
by cotton
• Defensins - plant proteins that
disrupt bacterial and fungal cell
membranes
• Lysosomes
```
48
Describe the antifungal compounds made by plants
```
• e.g. phenols - antifungals madden
many different plants
• Antifungal gossypol produced by
cotton
• Caffeine - toxic to fungi and
insects
• Saponins - chemicals in many
plant cell membranes that interfere
with fungal membranes
• Chitinases - enzymes that break
down the chitin in fungal cell walls
```
49
Describe what animal nonspecific responses are
• Always present or activated very
rapidly
• Defends against all pathogens in
the same way
50
What are non-specific defences keeping pathogens
| out?
```
Skin
• Covers the body and prevents the
entry of pathogens
• Skin flora: healthy microorganisms
that outcompete pathogens for
space on the body surface
• Produces sebum - oily substance
stops the growth of pathogens
Mucous membranes
• Lines many of the body tracts,
including the airways of the gas
exchange system
• Secrete sticky mucus
• Traps microorganisms and
contains lysozymes, which destroy
bacterial and fungal cell walls
• Also contains phagocytes, which
remove remaining pathogens
• Lysozymes in tears, urine and
stomach acid also help to prevent
pathogens entering the body
Expulsive reflexes:
• coughs and sneezes eject
pathogen-laden much from the
gas exchange system
• Vomiting and diarrhoea expel the
contents of the gut along with any
infective pathogens
```
51
What happens when you cut yourself?
```
• The skin breached and pathogens
can enter the body
• The blood clots rapidly to seal the
wound
• When platelets come into contact
with collagen in skin or the wall of
the damaged blood vessel, they
adhere and begin secreting several
substances
```
52
What are the substances secreted by platelets?
```
• Thromboplastin - an enzyme that
triggers a cascade of reactions
resulting in the formation of a
blood clot (or thrombus)
• Serotonin - makes the smooth
muscle in the walls of the blood
vessels contract, so they narrow
and reduce the supply of blood to
the area
```
53
What happens to the clot next?
```
1. The clot dries out forming a
hard, tough scab that keeps
pathogens out
2. Epidermal cells below the scab
begin to grow, sealing the wound
permanently, while damaged
blood vessels regrow
3. Collagen fibres are deposited to
give the new tissue strength
4. Once the new epidermis reaches
a normal thickness, the scab
sloughs off, and the wound is
healed
```
54
What is an inflammatory response?
```
A localised response to pathogens
(or damage or irritants) resulting in
an inflammation at the site of a
wound
• Inflammation - biological response
of vascular tissues to pathogens,
damaged cell or irritants, resulting
in pain, heat, redness and swelling
```
55
Describe the steps in an inflammatory response
```
1. Mast cells are activated in
damaged tissue and release
chemicals called histamines and
cytokines
2. Histamines make the blood
vessels dilate, causing localised
heat and redness. The raised
temperature helps prevent
pathogens from reproducing
3. Histamines make blood vessel
walls more leaky, so blood
plasma is forced out. This tissue
fluid causes swelling (oedema)
and pain
4. Cytokines attract phagocytes to
the site, and dispose of
pathogens by phagocytosis
Widespread infections can cause a
whole body rash
```
56
What are the non-specific defence methods for getting
| rid of pathogens?
* Fevers
* Phagocytosis
* Helpful chemicals
57
Describe fevers
```
When a pathogen invades the body,
cytokines stimulate your
hypothalamus to reset the
thermostat and your temperature
goes up
• Higher temperatures inhibit
pathogen reproduction
• The specific immune system
works faster at higher
temperatures
```
58
What is phagocytosis?
```
The process by white white blood
cells called phagocytes recognise
non-self cells, engulf them, and
digest them within a vesicle called a
phagolysosome
• Phagocytes build up at the site of
an infection and attack pathogens
• Pus consists of dead neutrophils
and pathogens
```
59
What is a phagosome?
The vesicles which a pathogen or
damaged cell is engulfed by a
phagocyte
60
What are the stages of phagocytosis?
```
1. Pathogens produce chemicals
that attract phagocytes
2. Phagocytes recognise nonhuman
proteins on the
pathogen. This is a respondent
to a specific type of pathogen,
but simply a cell or organism that
is non-self
3. The phagocyte engulfs the
pathogen and encloses it in a
vacuole called a phagosome
4. The phagosome combines with
a lysosome to form a
phagolysosome
5. Enzymes from the lysosome
digest and destroy the pathogen
```
61
What happens when a macrophage has digested a
| pathogen?
```
1. It combines antigens from the
pathogen surface membrane
with special glycoproteins in the
cytoplasm called the major
histocompatibility complex
(MHC)
2. The MHC complex movs these
pathogen antigens to the
macrophage’s own surface
membrane, becoming an
antigen-presenting cell (APC)
3. These antigens now stimulate
other cells involved in the
specific immune system
response
```
62
What are the helpful chemicals?
* Cytokines
| * Opsonins
63
How do cytokines help?
```
• Phagocytes that have engulfed a
pathogen produce chemicals
called cytokines
• Cytokines act as cell-signalling
molecules, informing other
phagocytes that the body is under
attack and stimulating them to
move to the site of infection or
inflammation
• Cytokines can also increase body
temperature and stimulate the
specific immune system
```
64
How do opsonins help?
```
Opsonins are chemicals that bind to
pathogens and tag them so they are
recognised more easily by
phagocytes, e.g. antibodies
• Phagocytes have receptors on
their cell membranes that bind to
common opsonins and the
phagocyte then engulfs the
pathogen
• Different opsonins, but antibodies
such as immunoglobulin G (IgG)
and immunoglobulin M (IgM) have
the strongest effect
```
65
How can counting blood cells indicate what type of response is taking place?
```
• Examine microscope slides of
blood smears
• Stain to show the nuclei of
lymphocytes
• Identifying the numbers of different
types of lymphocytes in a blood
smear indicates if a non-specific
or a specific immune response is
taking place
```
66
# Define the following:
1. Antibodies
2. Antigen
3. Antigen-antibody complex
```
1. Y-shapes glycoproteins made by
B cells of the immune system in
response to the presence of an
antigen
2. Identifying chemical on the
surface of a cell that triggers an
immune response
3. The complex formed when an
antibody binds to an antigen
```
67
Describe the specific immune system
```
aka active or acquired immunity)
• Slower than non-specific
responses
• Immune memory cells mean that it
reacts very quickly to a second
invasion by the same pathogen
```
68
Describe antibodies in detail
```
• Y-shaped glycoproteins called
immunoglobulins
• Bind to a specific antigen on the
pathogen or toxin that has
triggered the immune response
• Specific antibody for each antigen
• Made up of two identical long
polypeptide chains called heavy
chains, and two much shorter
chains called the light chains
• The chains are held together by
disulphide bridges, and there are
also disulfide bridges within the
polypeptide chains holding them in
shape
```
69
How do antibodies bind to antigens?
```
With a protein-based ‘lock-and-key’
mechanism similar to the
complementarity between the active
site of the enzyme and its substrate
• Binding site is an area of 110
amino acids on both the heavy
and the light chains known as the
variable region
• Variable region is a different shape
on each antibody and gives the
antibody its specificity
• The rest of the antibody molecule
is always the same, so is called
the constant region
```
70
What happens when an antibody binds to an antigen?
```
It forms an antigen-antibody
complex
• The hinge region of the antibody
provides the molecule with
flexibility
• This allows it to bind to 2 separate
antigens, one at each of its
antigen-binding sites
```
71
How do antibodies defend the body?
```
1. The antibody of the antigenantibody
complex acts as an
opsonin so the complex is easily
engulfed and digested by
phagocytes
2. Most pathogens can no longer
effectively invade the host cells
once they are part of an antigenantibody
complex
3. Antibodies act as agglutinins
causing pathogens carrying
antigen-antibody complexes to
clump together. This helps
prevent them spreading through
the body and makes it easier for
phagocytes to engulf a number
of pathogens at the same time
```
72
What are agglutinins?
Chemicals (antibodies) that cause
pathogens to lump together so they
are eager for phagocytes to engulf
and digest
73
What are lymphocytes?
```
White blood cells that make up the
specific immune system
• B lymphocytes mature in the Bone
marrow
• T lymphocytes mature in the
Thymus gland
```
74
What are the main types of T lymphocytes?
* T helper cells
* T killer cells
* T memory cells
* T regulatory cells
75
Describe the T helper cells
```
• Have CD4 receptors on cellsurface
membranes, which bind to
the surface antigens on APCx
• Produce interleukins (type of
cytokine)
• The interleukins made stimulate
the activity of B cells, which
increases antibody production,
stimulates production of other
types of T cells, and attracts and
stimulates macrophages to ingest
pathogens with antigen-antibody
complexes
```
76
Describe T killer cells
```
• Destroy the pathogen carrying the
antigen
• Produce a chemical called
perforin, which kills the pathogen
by making holes in the cell
membrane so it is freely
permeable
```
77
Describe T memory cells
```
• Live for a long time and are part of
the immunological memory
• If they meet an antigen a second
time, they divide rapidly to form a
huge number of clones of T killer
cells that destroy the pathogen
```
78
Describe T regulator cells
```
• Suppress the immune system,
acting to control and regulate it
• Stop the immune response once a
pathogen has been eliminated
• Makes sure the body recognises
self antigens and doesn’t set up an
autoimmune response
• Interleukins are important in this
control
```
79
What are the main types of B lymphocytes?
* Plasma cells
* B effector cells
* B memory cells
80
Describe Plasma cells
```
• Produce antibodies to a particular
antigen and release them into the
circulation
• An active plasma cell only lives for
a few days
• Produces around 2000 antibodies
per second whilst alive and active
```
81
Describe B effector cells
These divide to form the plasma cell
| clones
82
Describe B memory cells
```
• Live for a very long time and
provide the immunological
memory
• Programmed remember a specific
antigen and enable the body to
make a very rapid response when
a pathogen carrying that antigen is
encountered again
```
83
What happens in cell-mediated
| immunity?
```
T lymphocytes respond to the cells
of an organism that have been
changed in someway, e.g. by a virus
infection, by antigen processing or
by mutation (e.g. cancer cells) and
cells from transplanted tissue
```
84
When is the cell-mediated response particularly
| important?
Against viruses and early cancers
85
What are the stages in cell mediated immunity?
```
1. In the non-specific defence
system, macrophages engulf
and digest pathogens in
phagocytosis. They process the
antigens from the surface of the
pathogen to form APCs
2. The receptors on some the T
helper cells fit the antigens.
These cells become activated
and produce interleukins which
stimulate more T cells to divide
by mitosis. They form clones of
activated T helper cells that all
carry the right antigen to bind to
a particular pathogen
3. The cloned T cells may:
• Develop into T memory cells
• Produce interleukins that stimulate
phagocytosis
• Produce interleukins that stimulate
B cells to dive
• Stimulate the development of a
clone of T killer cells that are
specific for the presented antigen
and then destroy infected cells
```
86
What happens in humoral immunity?
```
The body responds to antigens
found outside the cells e.g. bacteria
and fungi, and to APCs
• The humoral immune system
produces antibodies that are
soluble in the blood and tissue
fluid are not attached to cells
```
87
How does humoral immunity work?
```
• B lymphocytes have antibodies on
their cell surface membrane
• When a pathogen enters the body
it will carry specific antigens, or
produce toxins that act as
antigens
• A B cell with the complementary
antibodies will bind to the antigens
on the pathogen, or to the free
antigens
• The B cell engulfs and prowesses
the antigens to become an APC
```
88
What are the steps in humoral immunity?
```
1. Activated T helper cells bind to
the B cell APC. This is clonal
selection - the point at which the
B cell with the correct antibody
to overcome a particular antigen
is selected for cloning
2. Interleukins produced by the
activated T helper cells activate
the B cells
3. The activated B cell divides by
mitosis to give clones of plasma
cells and B memory cells. This
clonal expansion
4. Primary immune response:
Cloned plasma cells produce
antibodies that fir the antigens
on the surface of the pathogen,
bind to the antigens and disable
them, or act as opsonins or
agglutinins
5. Secondary immune response:
Some cloned B cells develop
into B memory cells. If infected
by the same pathogen again, the
B memory cells die rapidly to
form plasma cell clones
```
89
What is an autoimmune disease?
A condition or illness resulting from
| an autoimmune response
90
What is an autoimmune response?
```
Response when the immune system
acts against its own cells and
destroys healthy tissue in the body
• Genetic tendency in some families
• Sometimes the immune system
responds abnormally to a mild
pathogen or normal body
microorganisms
• In some cases the T regulator cells
don’t work effectively
```
91
What can be used to treat autoimmune diseases?
```
Immunosuppressant drugs, which
prevent the immune system from
working, but they also deprive the
body of its natural defences against
communicable diseases
```
92
Describe 3 autoimmune diseases
```
Type 1 diabetes - The insulinsecreting
cells of the pancreas
• Insulin injections
• Pancreas transplants
• Immunosuppressant drugs
Rheumatoid arthritis: Jointsespecially
in the hands, wrists,
ankles and feet
• No cure
• Anti-inflammatory drugs
• steroids
• Immunosuppressants
• Pain relief
Lupus: Often affects skin and joints
and causes fatigue. Can attack any
organa in the body including
kidneys, liver, lungs or brain
• No cure
• Anti-inflammatory drugs
• Steroids
• Immunosuppressants
• Various
```
93
What is natural active immunity?
```
Immunity which results from the
response of the body to the invasion
of a pathogen
• It is known as active because the
body has itself acted to produce
antibodies and/or memory cells
```
94
What is natural passive immunity?
```
The immunity given to an infant
mammal by the mother through the
placenta and the colostrum
• Within a few days of birth, a
breast-fed baby will have the same
level of antibody protection
against disease as the mother
• Lasts until the immune system of
the baby begins to make its own
antibodies
• The antibodies the baby receives
from the mother are likely to be
relevant to pathogens in its
environment, where the mother
has acquired them
```
95
What is colostrum?
```
The first milk a mammalian mother
makes
• Very high in antibodies
• The infant gut allows these
glycoproteins to pass into the
bloodstream without being
digested
```
96
What is artificial passive immunity?
```
Immunity which results from the
administration of antibodies from
another animal against a dangerous
pathogen
• Temporary immunity but can be
lifesaving
• e.g. used in tetanus and rabies
```
97
How can tetanus be treated with artificial passive
| immunity?
```
Tetanus is caused by a toxin
released by the bacterium
Clostridium tetani, found in soil and
animal faeces
• Causes the muscles to go into
spasm so you cannot swallow or
breathe
• People who might be infected will
be injected with tetanus antibodies
extracted from the blood of horses
• This prevents the development of
the disease, but doesn’t provide
long-term immunity
```
98
What is artificial active immunity?
```
Immunity which results from
exposure to a safe form of a
pathogen, e.g. by vaccination
• The body is stimulated to make its
own antibodies to a safe form of
an antigen (a vaccine), which is
injected into the bloodstream
(vaccination)
```
99
What type of pathogen may vaccines contain?
```
• Killed or inactivated bacteria and
viruses, e.g. whooping cough
(pertussis)
• Attenuated (weakened) strains of
live bacteria or viruses e.g. rubella,
BCG against TB, polio (vaccine
taken orally)
• Toxin molecules that have been
altered and detoxified, e.g.
diphtheria, tetanus
• Isolated antigens extracted from
the pathogen e.g. the influenza
vaccine
• Genetically engineered antigens
e.g the hepatitis B vaccine
```
100
What are the main steps in vaccination?
```
1. The pathogen is made safe so
that the antigens are intact but
there is no risk of infection
2. Small amount of safe antigen,
known as the vaccine, are
injected into the blood
3. The primary immune response is
triggered by the foreign antigens
and your body produces
antibodies and memory cells as
if you were infected with a live
pathogen
4. If you come into contact with a
live pathogen, the secondary
immune response is triggered
and you destroy the pathogen
rapidly before you suffer
symptoms of the disease
```
101
What is an epidemic?
When a communicable disease
spreads rapidly to a lot of people at
a local or national level
102
What is a pandemic?
When a communicable disease
spreads rapidly to a lot of people
across a number of countries
103
What is herd immunity?
```
When a significant number of people
in the population have been
vaccinated, this gives protection to
those who do not have immunity.
This is known as herd immunity, as
there is minimal opportunity for an
outbreak to occur
```
104
Give examples of diseases that cannot yet be prevented by vaccination
```
Malaria
• Plasmodium, the protoctist that
causes malaria
• It is very evasive - spends its time
inside the erythrocytes so it is
protected by self antigens from the
immune system, and within an
infected individual, its antigens
reshuffle
HIV (which causes AIDS)
• It enters the macrophages and T
helper cells, so it has disabled the
immune system itself
```
105
Describe the history of Penicillin
```
The first widely used, safe antibiotic,
derived from a mould, Penicillium
notatum
• Discovered by Alexander Fleming
in 1928, when he found it growing
on bacteria cultures
• Howard Florey and Ernst Chain to
develop an industrial process for
making the new drug, which has
since saved millions of lives
around the world
```
106
How are drugs designed nowadays?
```
Using complex computer
programmes
• They can build up 3D models of
key molecules in the body, and of
pathogens and their antigen
systems
• Models of potential drug
molecules are built up which are
targeted at specific areas of a
pathogen
• Computers are used to search
through libraries of chemicals to
isolate any with a potentially useful
action against a specific pathogen
```
107
What is pharmacogenomics?
```
The science of interweaving
knowledge of drug actions with
personal genetic material
We know that genotypes and drugs
interact
```
108
What does synthetic biology
| involve?
```
Using the techniques of genetic
engineering, we can develop
populations of bacteria to produce
drugs that would otherwise be
unavailable.
• Synthetic biology enables the use
of bacteria as biological factories
• Nanotechnology is another strand
of synthetic biology where tiny,
non-natural particles are used for
biological purposes e.g. to deliver
drugs to very specific sites within
the cells of pathogens or tumours
```
109
What is selective toxicity?
```
The ability to interfere with the
metabolism of a pathogen without
affecting the cells of the host
• e.g. antibiotics interfere with the
metabolism of the bacteria without
affecting the metabolism of the
human cells
```
110
What are antibiotic-resistant bacteria?
Bacteria that undergo mutation to
become resistant to an antibiotic
and then survive to increase in
number
111
How does antibiotic resistance occur in bacteria?
```
If a random mutation during
bacterial reproduction produces a
bacterium that is not affected by the
antibiotic, that is the one which is
best fitted to survive and reproduce,
passing on the antibiotic resistance
mutation to the daughter cells
```
112
What are the causes for the rise in antibiotic resistance?
```
• Over prescription of antibiotics to
people
• Adding antibiotics animal feed to
prevent losing animals due to
bacterial conditions and reducing
business profits
```
113
Describe MRSA
Describe MRSA
114
Describe C.difficile
```
Bacterium in the guts of about 5%
of the population
• Produces toxins that damage the
lining of the intestines, leading to
diarrhoea, bleeding and even
death
• Not a problem for healthy people,
but when commonly-used
antibiotics kill off much of the
‘helpful’ gut bacteria, it survives,
reproduces and takes hold rapidly
```
115
How can antibiotic-resistant infections be reduced in the long-term?
```
• Minimising the use of antibiotics,
and ensuring the every course of
antibiotics is completed to reduce
the risk of resistant individuals
surviving and developing into a
resistant strain population
• Good hygiene in hospitals, care
homes and in general - this has a
major impact on the spread of all
infections, including antibioticresistant
strains
```
