4.5 Immunology And Disease Flashcards
Pathogenic definition
An organism that causes damage to its host
Infectious definition
A disease that may be passed or transmitted from one individual to another
Carrier definition
A person who shows no symptoms when infected by a disease organism but can pass the disease to another individual
Disease reservoir definition
Where a pathogen is normally found; this may be humans or another animal and may be a source of infection
Endemic definition
A disease, which is always present at low levels in an area
Epidemic definition
Where there is a significant increase in the usual number of cases of a disease often associated with a rapid spread
Pandemic definition
An epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people
Vaccine definition
Uses non-pathogenic forms, products or antigens of micro-organisms to stimulate an immune response which confers protection against subsequent infection
Antibiotics definition
Substances produced by microorganisms which affect the growth of other microorganisms
Antibiotics resistance definition
Where a microorganism, which should be affected by an antibiotic, is no longer susceptible to it
Vector definition
A living organism which transfers a disease from one individual to another
Toxin definition
A chemical produced by a microorganism which causes damage to its host
Antigenic types definition
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
Points to consider about the statement the human body acts as a host to other living organisms
• Many organisms live in or on the human body
• can be in a symbiotic or parasitic relationships
Type of organism does cholera involve
Gram negative bacterium
Source of infection of cholera
Contaminated food or water
Tissue affected with cholera
Gut lining
• toxins affect gut lining so chloride channel proteins are affected and water and ions aren’t absorbed into blood
• patient has severe watery diarrhoea which leads to severe dehydration and frequently death
Mode of transmission of cholera
Water supplies
• humans act as reservoirs or carriers and contaminate water supplies
• only multiplies in the human host
Prevention of cholera
• treatment of water
• good hygiene
• provision of clean drinking water
Control methods and treatment of cholera
Antibiotics
Rehydration mainly
Vaccine of cholera
• temporary protection
Numbers of cholera in the world
Endemic is some areas
Type of organism in tuberculosis
Bacillus bacterium
Source of infection of tuberculosis
Inhalation of bacteria laden droplets from coughs and sneezes
Tissue affected with tuberculosis
Lungs and neck lymph nodes
• long term lung damage
• coughing, chest pain and coughing up blood
Mode of transmission of tuberculosis
Airborne droplets
• rapid spread in overcrowded places
Prevention of tuberculosis
• identifying people with active TB to stop spread
Control methods and treatment of tuberculosis
Long course of antibiotics
Vaccine
Vaccine of tuberculosis
BCG
given to children
Numbers of tuberculosis in the world
On the rise partly due to the link with the HIV epidemic
Type of organism with smallpox
Virus
Source of infection of smallpox
Inhalation/close contact with infected person
Tissue affected with smallpox
Blood vessels of skin, mouth and throat
• dispenses around the body
• fluid filled blisters, blindness and limb deformities
Mode of transmission of smallpox
Airborne/contact
Prevention of smallpox
Eradicated since 1980
• made deliberately extinct by humans
Control methods and treatment of smallpox
Before the vaccine - isolation to stop spread
Vaccine of smallpox
Successful immunisation program
• low rate of antigenic variation
• highly effective
• produces a strong immune response
• no animal resevoir
Type of organism of influenza
Virus
3 subgroups
Each with many different antigenic types
Source of infection of influenza
Inhalation of droplets from coughs and sneezes
Tissue affected by influenza
Cells lining upper respiratory tract
• causes sore throat, coughing and fever
Mode of transmission of influenza
Airborne droplets
Prevention of influenza
Regular hand washing
using and discarding tissues for coughs snd sneezes
Control methods and treatment of influenza
Quarantine and hygiene
Mode of transmission is difficult to control
Antibiotics are ineffective - used to treat symptoms of secondary bacterial infection
Vaccine of influenza
Annual vaccine
• surface antigens on virus change - need annual vaccine
• not always effective due to the number of different types
Type of organism of malaria
Protoctistan
Name of parasite of malaria
Plasmodium
Source of infection of malaria
Biting by mosquitoes
Tissue affected by malaria
Liver and red blood cells
• initially invades liver cells
• multiplies in rbc which burst
• when rbc burst they release more parasites and toxins which cause severe bouts of fever
Mode of transmission of malaria
Vector - female anopheles mosquitos
• feeds on blood which contains sexually reproducing stage of plasmodium
• infective stage migrates from gut of mosquito to salivary gland and therefore transmit parasite to new victim
Vector of malaria
Female anopheles mosquito
Prevention of malaria
Knowledge of mosquito and plasmodium life cycle required in order to exploit their weak points
Prevention measures used to prevent malaria responding to mosquito behaviour
• sleep under nets
• nets are treated with the pyrethroid insecticide
• drain or cover stagnant water
• film of oil on the water
Reason for effect of sleeping under nets to prevent malaria
Mosquitoes feed between dusk and dawn
Reason for effect of treating nets with insecticide to prevent malaria
Kills mosquitoes
Reason for effect of draining or covering stagnant water to prevent malaria
Removes mosquitoes access to egg-laying sites
Reason for effect of making a film of oil on the water to prevent malaria
Lowered surface tension prevents larvae piercing surface to get oxygen
What is a biological control
Use of a living species to control a pest
Biological controls used to prevent malaria
• fish introduced into water
• infecting mosquitos with bacterium wolbachia
• male mosquitoes are sterilised with x-rays
Reason for effect of introducing fish into water to prevent malaria
Larvae are aquatic so the fish eat them
Reason for effect of infecting mosquitoes with bacterium wolbachia to prevent malaria
Wolbachia blocks plasmodium development in the mosquitoes
Reason for effect of sterilising male mosquitoes with x-rays to prevent malaria
After they mate, no off-spring are reduced
Control methods and treatment of malaria
•Drug treatments to mainly reduce chance of infection
•Resistance is an increasing problem
•Plasmodium is only affected by drugs outside the cells in the blood only - this limits effectiveness and there are side effects
Vaccine of malaria
• difficult to develop due to mutations
• many antigenic types
• only effective when parasite is outside body cell - there is limited target stages
What does it mean that viruses are intracellular parasites
They’re inert outside the host cell
They use a cell’s metabolic pathways to produce more virus paricles
Lytic cycle
• immediately reproduce using host metabolism to copy their own nucleic acid and synthesise new protein coat
• immediate symptoms
• release may be by lysis or host cell (eg common cold) or budding (eg influenza)
Lysogenic cycle
• integrate their nucleic acid into host cell genome - may stay there for many cell generations with no clinical effect
• enters lytic cycle at later time - symptoms are then produced
• eg herpes, HIV
What is pathogenicity?
The ability of a pathogenic agent to cause disease
Which ways can viruses be pathogenic?
• cell lysis
• toxins production
• cell transformation
• immune supression
How can a virus be pathogenic through cell lysis
• bacteria - pressure of new virus particles inside cause bacteria to burst
• animal - inflammation caused by T-lymphocytes or antibodies cause lysis
• after cell lysis viruses escape to infect other cells/organisms
How can a virus be pathogenic through toxin production
• many viral components and their by-products are toxic
• not fully understood
How can a virus be pathogenic through cell transformation
• viral DNA can integrate into host chromosome
• if it inserts into a pro-oncogene/tumor suppressor gene which cab result in the cell undergoing rapid, uncontrolled division which can become cancerous
How can a virus be pathogenic through immune suppression
• suppression of reactions that cause B and T lymphocytes to mature and so there’s a reduction in antibody formation
• reduction of phagocytic cells engulfing microbes
• eg HIV causes sufferes to be immune compromised - they’re very susceptible to infection
Antibiotics
• produced by fungi
• act on bacteria
• dont act on viruses or eukaryotic cells due to absence of metabolic pathways
• treat bacterial infection without harm to patient
What are the two mode of actions of antibiotics
Bactericidal and bacterisostatic
Bactericidal mode of action of antibiotics
• kills the bacteria
• eg penicillin
Bacteriostatic mode of action of antibiotics
• prevents growth but doesn’t cause death
• inhibits protein synthesis
• eg tetracycline
Broad-spectrum antibiotics
• affect many different gram-positive and gram-negative species
• tetracycline and ampicillin
Narrow-spectrum antibiotics
• more selective than broad spectrum
• eg penicillin G which only kills gram-positive bacteria
Penicillin mode of action and spectrum
Bactericidal
Narrow spectrum
Where penicillin produced from
The fungus Penicillium notatium
How does penicillin kill bacterial cells
• affects formation of cross linkages in the peptidoglycan of the cell wall during growth and division of bacterial cells - binds to and inhibits the enzyme responsible for the formation of these cross-linkages
• this weakens the wall
• when osmotic changes occur and water enters the cells the cells lyse and die
Which kind of bacteria is penicillin more effective against and why
Gram positive
Difference in cell wall structure
Tetracycline mode of action and spectrum
Bacteriostatic
Broad spectrum
Which fungus is tetracycline produced from
Streptomyces
How does tetracycline inhibit the growth of bacterial cells
• affects protein synthesis which is a metabolic process common to all bacteria
• tetracycline diffuses and is pumped into bacteria cells
• acts as a competitive inhibitor of the 2nd anticodon binding site on the 30s subunit of bacterial ribosomes
• this prevents the binding of a tRNA molecule to it’s complementary codon
• inhibits the translation stage of protein synthesis
What do bacteria do under optimum conditions and what does this result in
Divides rapidly
High mutation rate
How can the overuse of antibiotics result in the spread of antibiotic resistance?
• some mutations confer antibiotic resistance so that these bacteria have a selective advantage in the presence of antibiotics - when they encounter antibiotic they’re not affected by it and continue to replicate whilst other non-mutated forms die
• overuse of antibiotics results in accidental selection of bacterial strains that are completely unaffected by some antibiotics
What is the danger of the spread of antibiotic resistance among pathogenic bacteria
If they cause an infection it becomes increasingly difficult to control
How is the skin a natural barrier?
• physical barrier
• collagen in connective tissue of dermis that is maintained by vitamin C- tough
• keratin in epidermal cells to make the skin waterproof
How is skin microflora a natural barrier?
Offers protection by competing with pathogenic bacteria
• flora isn’t easily removed by washing unlike the bacteria
How is ciliated mucous membranes a natural barrier?
• mucus trap microbes in inhaled air
• cilia brush/sweep the mucus away from the lungs
How are tears, mucus and saliva natural barriers?
• contain lysozyme which is an enzyme that hydrolyses peptidoglycan in bacterial cell walls
• weakened cell wall breaks as water from tears and saliva enters microbe by osmosis which causes cells to lyse - killing the bacteria
How is stomach acid a natural barrier?
Kills ingested bacteria in food and drink
pH 2
If there is a breach of skin how do blood clots act as a natural barrier?
Seal wounds
Which prevents entry of microbes
If there is a breach of skin how does inflammation act as a natural barrier?
• to localise breaks in the barrier
• there is increased blood flow to the area which brings a large number of phagocytic cells
• broken capillaries heal
• raised temperature as it is unfavourable to microbes and decreases their growth
How does phagocytosis act as a natural barrier once skin has been breached?
They destroy invading microbes by engulfing and digesting them
Macrophages and neutrophiles
Are natural barriers specific or non-specific responses to microbes
Non-specific
Why are specific immune responses developed
As a result of antigens being recognised as foreign to the body
What is produced following humoral response
Antibodies
Which lymphocytes are involved in humoral response
B lymphocytes
Where fo B lymphocytes originate and mature
Originate - stem cells in bone marrow
Mature - spleen and lymph nodes
What do B lymphocytes contain to detect their specific antigens and what does this activation stimulate?
Each has receptors for the detection of its specific antigen
Activation stimulates the proliferation of B lymphocytes by mitotic division which differentiate to from plasma and memory cells
What do plasma cells do during humoral response
Release antibodies
What do memory cells do during immune response
Remain dormant in the circulation ready to divide if the same antigen is encountered again
What are antibodies
• Proteins - globulins, quaternary
• Specific to the antigen which they bind to to form an antigen-antibody complex
• Y-shaped
• 4 polypeptide chains
• 2 binding sites
Shape of antibody
Y shaped
How many polypeptide chains and binding sites do antibodies have
4 polypeptide chains
2 binding sites
What does the fact that antibodies have 2 binding sites mean
• 2 different antigens can be joined by 1 antibody
• hinge region is flexible so can bind to 2 antigens when they’re different distances apart
• allows for agglutination
How does agglutination increase the rate of engulfment by phagocytes
If viruses or toxins are joined by agglutination then they’re too large to enter the cell
What does the cell mediated response involve
Activation of T lymphocytes, phagocytic cells and B lymphocytes
Where do T lymphocytes originate from and where are they activated
Originate - stem cells
Activated - thymus gland
What causes the proliferation of T lymphocytes
Detection of the corresponding specific antigen
What do macrophages do in initiate response when they come across a microbe
Engulf the microbes then display the antigens of the microbe on their cell surface
They’re antigen presenting cells
What are the sub populations of T cells as T lymphocytes differentiate
T killer
T helper
T memory
What do t killer cells do
Cause lysis of the target cells
What do T memory cells do
Remain dormant in the circulation and then divide to form more T lymphocytes if the same antigen is encountered again in the future
What do T helper cells do
• release cytokines which
- stimulate B lymphocytes to initiate antibody response
- stimulate phagocytosis by macrophages
- stimulate colonal expansion of B and T lymphocytes - mitosis results in a large population of cells specific to that particular antigen
Explain primary immune response
• first exposure to a foreign antigen
• short latent period as macrophages carry out phagocytosis and incorporate the foreign antigen into their cell membrane
• t helper cells detect the antigens and secrete cytokines and stimulate B lymphocytes and macrophages
• B cells are activated and proliferate into plasma and memory cells
• low levels of antibody is secreted over 2-3 weeks as they clear the infection and symptoms disapear
Explain secondary immune response
• re-exposure to same anitgen
• very short latent period due to memory cells
• very small amount of antigen is needed to stimulate rapid plasma cell production
• antibody levels increase to between 10 and 100 times greater than initial response in a very short time
• antibody levels stay high for longer
• no symptoms develop
What is natural immunity and 2 examples
Immunity when no medical stimulation is involved
Catching the disease
Antibodies passed from mother to child
What is artificial immunity and examples
Medical intervention’s used
Vaccination programmes or in transfusion of antibodies
What is active immunity and examples
• when the individual produces antibodies
• long lasting protection due to production of memory cells
• natural - following infection
• artificial- following vaccination eg mmr
What is passive immunity and examples
• individual receives antibodies produced by another individual
• short lived protection as antibodies are recognised as non-self and destroyed so no memory cells are produced
• natural - antibodies transferred by placenta or breast milk
• artificial- pre synthesised antibody is injected into individual eg tetanus antitoxin
How do vaccines immunise people against disease eg rubella
Promotes a primary response without causing the disease as memory cells are produced
Active
What kind of injection is used to provide passive, emergency treatment against infection eg rabies
• antibodies can be injected to provide rapid protection against a pathogen
• rabies - allows time for the person’s immune system to develop an active immune response
• also used with people with a primary immune deficiency disease eg HIV, AIDS, as patients dont make enough antibodies and cannot provide enough protection against pathogens
What kind of antigenic variation will be more likely to be protected by a single round of immunisation and give example of infection that does this
Pathogens that exhibit no/low levels of it
Eg rubella
What is needed with organisms with many antigenic types and mutate frequently and what is the problem , give example of infection
• repeated immunisation against most common antigens
• wont be 100% effective
Eg influenza
What features do successful vaccines have
• they provoke a strong immune response- highly immunogenic and protect the individual from developing the disease
• they’ve little or no side effects that are mild in nature
• lead to long lasting immunity
Describe concept of herd immunity
• if enough are immune to the disease through vaccination there is a reduced reservoir of the pathogen in the population
• it provides protection to people who ate unable to be vaccinated because of compromised immune systems or illness
Which kind of ethical aspects should be taken into consideration when designing vaccination programmes?
• cost vs effectiveness
• protection of the individual compared to protection of the community
• rights of the individual when considering
- mandatory compared with voluntary
- side effects - are they real or perceived
- religious objections
- human rights
