C3: Immunology and disease Flashcards
Difference between endemic epidemic and pandemic
endemic: a disease, which is always present at low levels in an area
Epidemic: where there is a significant increase in the usual number of cases of a disease often associated with a rapid spread.
Pandemic: an epidemic occurring worldwide, or over a very wide area, crossing international boundaries and
usually affecting a large number of people
Define vaccine
vaccine: uses non-pathogenic forms, products or
antigens of micro-organisms to stimulate an immune
response which confers protection against subsequent
infection.
Define antibody and antigen
antibiotics: substances produced by microorganisms
which affect the growth of other microorganisms.
Antigen A molecuile that causes an immune response
Define antigenic type
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.
Cholera
Cholera is caused by a Gram negative bacterium vibrio chlolerae
Its toxins affect the gut lining causing watery diarrhoea leading to severe dehydration and frequently death.
Humans act as reservoirs or carriers and contaminate water supplies in
which the organism is transmitted, although it only multiplies in the human host.
Cholera prevention is by the treatment of water, good hygiene and the provision of clean drinking
water.
Antibiotic treatment is possible but treatment is largely by rehydration; vaccine (killed organism or possibly genetically engineered) may provide temporary protection.
tuberculosis
Tuberculosis is a bacterial disease casued by tuberculosis gram positive .
It can be transmitted by airborne
droplets when infected people cough and sneeze.
lungs and neck lymph nodes. are effected.
Symptoms include coughing, chest pain and coughing up blood.
Tuberculosis is prevented by a BCG vaccination programme for children. Treatment involves a long course of antibiotics.
Small pox
Smallpox. Is caused by the virus Variola major.
causes fluid filled blisters skin targets Mouth, throat,
lymph nodes, and
blood stream.
spread by comtaminated objects
organism is extinct (outside specialist
laboratories).
Low rate of antigenic variation/ mutation and the vaccine was highly effective.
In addition, there was no animal reservoir and people were keen to be
immunised because of the devastating effects of the disease.
Influenza
Influenza is caused by a virus of which there are three main sub-groups.
Within each subgroup there are many different antigenic types.
It infects cells lining the upper respiratory tract causing sore throat, coughing and fever.
Sufferers spread the disease by droplet infection.
Prevention includes quarantine and hygiene but influenza’s mode of spread is difficult to control.As
Antibiotics are ineffective against influenza and are only used to treat the symptoms of secondary bacterial infection.
Annual vaccination programmes are available but due to the number of types, together with the emergence of new types, they are not always effective.
Influenza
Influenza is caused by a virus of which there are three main sub-groups.
Within each subgroup there are many different antigenic types.
It infects cells lining the upper respiratory tract causing sore throat, coughing and fever.
Sufferers spread the disease by droplet infection.
Prevention includes quarantine and hygiene but influenza’s mode of spread is difficult to control.As
Antibiotics are ineffective against influenza and are only used to treat the symptoms of secondary bacterial infection.
Annual vaccination programmes are available but due to the number of types, together with the emergence of new types, they are not always effective.
Malaria
Malaria is caused by Plasmodium spp.,a protoctistan parasite. The disease is caused mainly by two species within which are many antigenic types.
The organism initially invades liver cells and then multiplies in red blood cells which burst, releasing more parasites and causing severe bouts of fever.
Female mosquitoes, feeding on
blood taken, act as vectors to transmit the parasite to new victims.
Stop the vector Nets, clothing, insect repellent, fish to eat larvae, drain breeding grounds, spray water surfaces with oil. Use insecticides,
bacterial infections of mosquitos, or
sterilisation of mosquitos.
Kill the parasite- drugs affect the parasite outside of blood cells but resistance is increasing.
Vaccine difficult as the parasite mutates, and antibodies only
help when the parasite is outside of blood cells.
How does a virus reproduce within a cell
A virus cannot reproduce on its own. It is an intracellular parasite and needs a host cell metabolism to
produce more virus particles. This causes pathogenic effects by:
- Viral DNA/RNA instructs the cell to make virus particles, when full cell lysis occurs, and the virus
escapes the cells to infect other cells/organisms (shedding) - Production of toxic substances
- Viral cell transformation, where they can trigger cells to become cancerous
- Viruses infecting white blood cells suppress the immune system (e.g. HIV).
Deescribe the difference between antigenic shift and drift
Antigenic Drift - No RNA proof reading enxymes so on average every replication a new viron has a new mutation producing a gradual change of surface proteins
Antigenic shift - when a cell is infected by a virus with two different antigeic types they can recombine giving rise to a new antigenic type with a combination of their surface proteins
Describe the difference between bacteriostaic and baactericidial
Bacteriostatic: prevents the growth of bacteria.
Bactericidal: kills bacteria.
Describe how penecillin works
Peptidoglycan bacterial cell walls are strengthened by polysaccharide cross-linked by amino acids. This stops osmotic lysis.
- Penicillin affects the formation of the cross links by inhibiting the enzyme that makes them. The wall is weakened and osmotic changes can cause cells to burst.
- Gram negative bacteria have an outer lipopolysaccharide
layer that protects the cells from penicillin.
describe how tetracycline works
Tetracycline acts as a competitive inhibitor of the second anticodonbinding site on the 30S subunit of bacterial ribosomes. It prevents the binding of a tRNA molecule to its complementary codon. This prevents protein synthesis common to all bacteria.
Tetracycline is a broader spectrum antibiotic.works on both negative and positive.
Describe the humoral response
Stem cells in the bone marrow
make B lymphocytes that mature
in the spleen and lymph nodes and
have receptors for the detection of
specific antigens on the surface of
foreign cells.
- When the B lymphocytes are
activated by a corresponding
antigen, they divide rapidly forming
antibody secreting plasma cells.
This clonal expansion is increased
by the cytokines from the cell
mediated response. - B lymphocytes also make
memory cells that remain in the
bloodstream and divide rapidly if
the antigen is encountered again
Describe the cell mediated response
Cell mediated immune response
1. Stem cells in the bone marrow make T lymphocytes, which are activated in the
thymus gland.
2. Detecting a foreign antigen causes proliferation of T lymphocytes as:
T killer cells which lysis the cell
Tmemory cells remain in the blood
T helper cells secrete cytokines
Describe the role of cytokines
Cytokines stimulate the clonal expansion of B cells and to produce antibodies.
Cytokines activate phagocytes to engulf and digest the foreign cells.
Describe Primary response
On first exposure to the antigen, there is a
latent period when antigen presenting cells
(including macrophages) carry out phagocytosis
and incorporate foreign antigen into their cell
membranes.
2. T helper cells detect these antigens and secrete
cytokines that stimulate B cells to undergo clonal
expansion and stimulate macrophages to carry out
phagocytosis.
3. Some B cells then differentiate to become antibodysecreting plasma cells with short lives. Others
become long-lived memory cells that retain the ability
to undergo mitosis in case of secondary infection.
there is a latent period then a Low level of antibody
is secreted, which
clears the infection
and
symptoms over a
period of 2 – 3 weeks.
Describe Primary response
On first exposure to the antigen, there is a
latent period when antigen presenting cells
(including macrophages) carry out phagocytosis
and incorporate foreign antigen into their cell
membranes.
2. T helper cells detect these antigens and secrete
cytokines that stimulate B cells to undergo clonal
expansion and stimulate macrophages to carry out
phagocytosis.
3. Some B cells then differentiate to become antibodysecreting plasma cells with short lives. Others
become long-lived memory cells that retain the ability
to undergo mitosis in case of secondary infection.
there is a latent period then a Low level of antibody
is secreted, which
clears the infection
and
symptoms over a
period of 2 – 3 weeks.
Describe the secondary response
Following re-exposure to the same
antigen, there is a very short latent
period due to the presence of memory cells. which undergo colonal expansion
Only a very small amount of antigen is
required to stimulate rapid production of plasma cells.
Antibody levels increase to
between 10 and 100 times
greater than the initial response
in a very short time frame.
Antibody levels stay high
for longer and no symptoms
develop.
Vaccines
- A vaccination stimulates
artificial active immunity
in an individual. - A vaccine must contain
an immunogenic antigen
that stimulates a strong
immune response. - Vaccinations for
pathogens that exhibit
low levels of antigenic
variation can protect
an organism after one
immunisation, e.g.
Rubella. - Some pathogens have
many antigenic types
and mutate frequently.
These require seasonally
repeated immunisations.
Immunisation programmes
require consideration of the
following: - cost vs effectiveness of
the vaccine - protection of the
individual compared
to protection of the
community - the rights of the
individual when
considering mandatory
compared or voluntary
programmes - side effects.
