Communicable Diseases 4.1 Flashcards
What are opsonins ?
-a type of antibody
-they are proteins that bind to the antigen on a pathogen to enhance the ability of phagocytic cells to bind and engulf the pathogen
What is a neutrophil ?
-the most common phagocyte
-they have a multi-lobed nucleus
-they are manufactured in the bone marrow
-they are shorted lived
-a large amount of them will be released as a result of infection
How do neutrophils act to destroy pathogens ?
-neutrophil binds to the opsonin attached to the antigen of the pathogen
-the pathogen is engulfed by endocytosis forming a phagosome
-lysosomes fuse to the phagosome and release lytic enzymes into it
-after digestion the harmless products can be absorbed into the cell
Define a neutrophil
A type of white blood cell that engulfs foreign matter and traps it in a large vacuole (phagosome) which fuses with lysosomes to digest the foreign matter
Define an antigen presenting cell
A cell that isolates the antigen from a pathogen and places it on the plasma membrane so that it can be recognised by other cells in the immune system
The special protein complex ensures that the antigen presenting cell is not mistaken for a foreign cell and attacked by other phagocytes
Define what a cytokine is
Hormone-like molecules used in cell signalling to stimulate the immune response
What are macrophages?
-larger than neutrophils
-manufactured in bone marrow and travel in the blood as monocytes before settling in the body tissue, many found in lymph nodes
What is the role of macrophages?
-play a role in initiating the specific response to invading pathogens
-when it engulfs a pathogen it does not fully digest it
-the antigen from the surface of the pathogen is saved and moved too a special protein complex on the surface of the cell (the cell becomes an antigen-presenting cell)
-through this other cells in the immune system can recognise the antigen
-special protein complex ensures the antigen-presenting cell is not mistaken as a foreign cell and attacked
What do antigen-presenting cells do?
They move around the body where it can come into contact with specific cells that can activate the full immune response
It increases the chances that an antigen will come into contact with them
What is clonal selection ?
Selection of a specific B or T cell that is specific to the antigen
What do T helper cells do?
They release cytokines (chemical messengers) that stimulate the B cells to develop and stimulate phagocytosis by the phagocytes
What do T killer cells do?
They attack and kill host-body cells that display the foreign antigen
They do this by making holes in the cell surface membrane using perforins
What do T memory cells do?
They provide long-term immunity
What do T regulator cells do?
They shut down the immune response after the pathogen has been successfully removed.They are also involved in preventing autoimmunity.
What are B and T lymphocytes?
-white blood cells that have a large nucleus and specialised receptors on their plasma membranes.
-both are made by bone marrow stem cells
-but B cells mature in the bone marrow
-and T cells mature in the thymus
What are the two types of cells that B lymphocytes develop into?
-plasma cells
-B memory cells
What are plasma cells?
-they circulate in the blood
-they manufacture and release antibodies
-they are responsible for immediate defence
What are B memory cells?
-don’t produce antibodies directly
-they remain in the body for a number of years and act as immunological memory
What are interleukins?
Signalling molecules that are used to communicate between different white blood cells
What is cell signalling ?
The communication between cells in the specific immune response.
The communication is achieved through the release of hormone-like chemicals called cytokines.
In order to detect a signal the target cell must have a cell surface receptor complementary in shape to the shape of the signalling molecule.
What are three examples of communication using cytokines?
-macrophages release monokines. Some monokines attract neutrophils (by chemotaxix-movement of cells towards a particular chemical.) Others stimulate B cells to differentiate and release antibodies
-T cells and macrophages release interleukins which can stimulate the clonal expansion(proliferation) and differentiation of B and T cells
-many cells can release interferon, which inhibits virus replication and stimulates the activity of T killer cells
What is clonal expansion?
An increase in the number of cells by mitotic cell division
What is an antigen?
-usually proteins or glycoproteins in the plasma membrane of the pathogen
-they will be recognised by the body as foreign by the immune system they are usually a marker on the surface of a cell
-this will stimulate the production of antibodies
What is an antibody?
-are immoglobulins- complex proteins produced by the plasma cells in the immune system
-they are released in response to an infection
- they have a region with a specific shape that is complementary to that of a particular antigen
-they attach to antigens and neutralise them making them harmless
-our immune system must manufacture one type of antibody for every antigen that is detected
What do opsonins do?
-they are a group of antibodies that bind to the antigens on a pathogen
-they act as binding sites for phagocytic cells so that these can more easily bind and destroy the pathogen
What do agglutinins do?
-as each antibody molecule has 2 identical binding sites it is able to ‘crosslink’ pathogens by binding an antigen on one pathogen with one binding site and then an antigen on another pathogen with its other binding site
-when many antibodies perform this function they clump together (agglutinate) pathogens
What are advantages of agglutinating pathogens?
-the agglutinated pathogens are physically impeded from carrying out some functions e.g. entering host cells also the pathogens are readily engulfed by phagocytes. This is particularly effective against viruses
What are anti-toxins?
-they bind to molecules released by the pathogenic cells
-these molecules may be toxic and anti-toxins render them harmless
What is the primary immune response?
-when an infecting agent is first detected the immune system starts to produce antibodies
-it takes a few days before the number of antibodies in the blood rises to a level that can combat the infection successfully
-once the pathogens have been dealt with number of antibodies in the blood drops rapidly
What is the secondary immune response?
-antibodies do not stay in the blood so if the body is infected a second time by the same pathogen the antibodies must be made again
-however as a result of the specific immune response there will be B memory cells and T memory cells circulating in the blood
-meaning these cells can recognise the specific antigens and the immune system can act more quickly
-so the production of antibodies starts sooner and is much more rapid , therefore the concentration of antibodies rises sooner and reaches a higher concentration
-the secondary immune response is normally quick enough to prevent any symptoms being detected by the host
What are 2 examples of diseases caused by bacteria?
-tuberculosis
-ring rot
What are 3 examples of diseases caused by viruses?
-HIV/ AIDS
-influenza
-tobacco mosaic virus
What are diseases caused by protoctista?
-malaria
-potato/tomato late blight
What are 2 diseases caused by fungi?
-black Sigatoka
-athlete’s foot
Define a pathogen
-a microorganism that causes disease
What type of cell is bacteria?
-prokaryote
How do bacteria damage cells?
-by releasing waste products and/or toxins
What are some examples of direct transmission?
-direct physical contact e.g. touching a person who is infected or contaminated surfaces (including soil) ,sexual contact
-faecal-oral transmission- eating or drinking contaminated food and water
-droplet infection- droplets from coughing or sneezing
-transmission by spores(made by fungi), that can be carried in the air or reside on surfaces or in soil
What are some examples of direct transmission?
-direct physical contact e.g. touching a person who is infected or contaminated surfaces (including soil) , kissing, sexual contact
-faecal-oral transmission- eating or drinking contaminated food and water
-droplet infection- droplets from coughing or sneezing
-transmission by spores(made by fungi), that can be carried in the air or reside on surfaces or in soil
What are some factors that can reduce direct transmission?
-hygiene- washing hands regularly (especially after toilet), cleaning and disinfecting cuts, using condoms
-treatment of waste water and drinking water, careful preparation and cooking of food
-catch it- bin it- kill it
-washing skin after contact with soil
What are some living conditions that affect transmission?
-climate- hot climates can increase spread of pathogens as they may reproduce quicker
-social factors- overcrowding, poor ventilation, poor education about the spread of disease, an area where less vaccines or medicines are available
What is indirect transmission?
-when a pathogen is passed from host to new host, via a VECTOR
What are some methods of transmission for a plant?
-pathogens that are present in soil enter the roots of a plant and infect it
-spores of fungi may be carried by the wind
What is an example of indirect transmission in plants?
—insects may act as a vector
What are some physical passive defences in a plant?
-cellulose cell wall- physical barrier, may contain a variety of chemical defences
-waxy cuticles-prevent water collecting on plant surfaces, pathogens collect on water and need it to survive.
-bark-normally contains chemical defences
-callose- polysaccharide that is deposited around the sieve plates and blocks the flow in the sieve tube
-tylose- can act as a plug in xylem vessel -to prevent spread through water. Also have a high concentration of terpenes that are toxic to pathogens
What is callose deposition?
-the deposition of callose between the plant cell wall and cell membrane near the invading pathogen
-Callose deposits are polysaccharide polymers that impede cellular penetration at the site of infection
-it strengthens the cell wall and blocks plasmodesmata
-it is an active defense
What are some examples of active defences in a plant?
-cell walls become thickened with additional cellulose
-oxidative bursts that produce highly reactive oxygen molecules capable of damaging the cells of invading organisms
-increase in chemical production
-necrosis-deliberate cell suicide. A few cells surrounding the infection are sacrificed ,this can limits pathogens access to water and nutrients
What is active immunity ?
-where the immune system is activated (as a result of infection) and manufactures its own antibodies
-a person suffers from the disease once and is then immune
What is passive immunity?
-immunity achieved when the antibodies are passed to the individual through breast feeding
-or through an injection (artificial)
What is natural immunity?
Immunity achieved through normal life processes (in the immune system as a result of infection)
What is artificial immunity?
-immunity provided by antibodies made in the immune system as a result of vaccination
What is an autoimmune disease?
-a condition in which the immune system attacks and destroys healthy body tissue
E.g. arthritis
What is arthritis?
-an autoimmune disease
-it is a painful inflammation of a joint
-the cause is uncertain, but it starts with antibodies attacking the membranes around a joint
What is personalised medicine?
-the potential development of designer medicines for individuals
Describe the process of phagocytosis
• Damaged cells and pathogens release cell-signalling chemicals (cytokines) that attract the phagocytes (macrophages and neutrophils)to the site of infection.
•An opsonin protein can attach to pathogens to mark them and make it easier for neutrophils and macrophages to engulf them
• Phagocytes have receptors which can attach onto chemicals on the surface of pathogens.
• The phagocyte then engulfs the pathogen into a vesicle to create a phagosome.
• Within the phagocytes, there are lysosomes which contain hydrolytic lysozyme enzymes.
• The lysosome fuses with the phagsome to expose the pathogen to the lyzozyme. The lysozyme hydrolyses the pathogen and any soluble useful molecules are absorbed into the cytoplasm of the phagocyte
• The phagocytes will present the antigen of the digested pathogen on their surface - they are then called antigen-presenting cells.
Define the term parasite
3marks
-lives in host
-gains nutrition from host
-at the harm of host
Explain why the human body’s primary defences do not prevent the entry of plasmodium into the body
(2marks)
-mosquito feeds on blood
-breaks skin, skin cannot act as barrier
How does a pathogen cause harm?
-by damaging tissue
-through the release of toxins
What is a characteristic of the bacterial disease tuberculosis ?
-a disease that affects many parts of the body, killing the cells and tissues; the lungs are most often affected
-transmitted through airborne droplets -more prevalent when people live in cramped conditions
What is a characteristic of the bacterial disease ring rot?
-infects plants
-ring of decay in the vascular tissue of a potato tuber or tomato, accompanied by leaf wilting
What is a characteristic of the viral disease HIV/AIDS?
-attacks T cells and compromises immune response the host is unable to produce an adequate immune response so is vulnerable to infections and cancer
-transmitted through direct contact e.g. unprotected sex, sharing needles
What is a characteristic of the viral disease influenza?
-attacks respiratory system (it infects the ciliates cells lining gas exchange surfaces) causes muscle pains and headaches
-people with lowered immune systems at higher risk of having severe symptoms
-transmitted by airborne droplets when coughing and sneezing
What is a characteristic of the viral disease tobacco mosaic virus?
-causes mottling and discolouration of leaves
-the damage prevents the plant from growing
What is a characteristic of the protoctista disease malaria?
-caused by plasmodium and is spread to humans through mosquitoes they act as the vector
-plasmodium infects red blood cells, the liver and the brain causes headache and fever and may progress to coma and death
What is a characteristic of the protoctista disease potato/tomato late blight?
-has hyphae which enter the plant and cause damage to the leaves and fruit
-transmitted by spores which travel on the wind or are transferred by animals and insects from one plant to another
What is a characteristic of the fungal disease Black Sigatoka?
-infects bananas
-the fungal hyphae cause damage to the leaves causing leaf spots this prevents plant growth and reduces yield
-transmitted by spores from one plant to the next through the wind
What is a characteristic of the fungal disease athlete’s foot?
-only infects humans
-transmitted by direct contact
-it causes the skin to crack and become scaly, causing itchiness and soreness
What is a characteristic of the fungal disease athlete’s foot?
-only infects humans
-transmitted by direct contact
-it causes the skin to crack and become scaly, causing itchiness and soreness
What do plants produce as a defence against pathogens?
-plants produce chemicals
E.g.
Terpenoids- a range of essential oils that have antibacterial and anti fungal properties
Phenols-have antibiotic and anti fungal properties. Also can inhibit attack by insects as if an insect ingests a high amount oof tannins they will die-they deactivate digestive enzymes.
Alkaloids-gives the plant a bitter taste, act on a variety of metabolic reactions via inhibiting or activating enzyme action. Prevents larger animals from grazing ,the plant will have less damage that will enable pathogens to enter
What are 6 examples of primary non-specific defences against pathogens in animals?
-skin
-blood clotting
-wound repair
-inflammation
-expulsion reflexes
-mucous membranes
How does skin act as a primary non specific defence in animals?
-cells produced by mitosis at the base of the epidermis, these migrate to the surface of the skin
-as they migrate they dry out and the cytoplasm is replaced by the protein keratin(keratinisation)
-the KERATINISED LAYER OF DEAD SKIN CELLS ACT AS A BARRIER TO PATHOGENS
How does blood clot and how does this act as a primary non-specific defence agaimst pathogens?
-platelets release substances that via a cascade of events, results in the formation of fibrin which itself forms a network, trapping platelets and forming a clot
-this will form a new barrier to prevent pathogens from entering
How does a wound repair?
-once a clot has formed, it begins to dry out and form a scab
-the scab shrinks as it dries drawing the sides of a cut together
-makes a temporary seal under which the skin is repaired
-first stage of skin repair is the deposition of fibrous collagen under the scab
-stem cells in the epidermis then divide by mitosis to form new cells, which then migrate to the edges of the cut and differentiate to form new skin
-new blood vessels grow to supply oxygen and nutrients to the new tissues
-the tissues contract to help draw the edges of a cut together so that the repair can be completed
-as the new skin is completed, the scab will be released
What are mucous membranes and how do they act as a primary non-specific defence against pathogens in animals?
-line many body tracts e.g.passages in the airway ,the epithelial layer contains globlet cells
-the mucus produces traps pathogens
-cilia move in a coordinated way to waft the layer of mucus away from the lungs to the top of the trachea where it can enter the oesophagus and be swallowed
-most pathogens killed by the acidity of the stomach as it denatures their enzymes
How do expulsive reflexes act as a primary non-specific defence against pathogens in animals?
-e.g. sneezing, coughing and vomitting
-they are mechanisms to force pathogens out the body
How does inflammation act as a primary non-specific defence against pathogens in animals?
-inflammation occurs in localised areas where damage to cells is detected. When cells are damaged this triggers mast cells to release histamines and cytokines
-histamines are released by mast cells and it causes vasodilation so more blood is flowing to this area
-increase in blood temperature can also kill pathogens
-histamines also make the walls of the blood vessels more permeable so more white blood cells can be delivered to the site of damage
What is vaccination?
-exposure to a form of a pathogen that has been rendered harmless, to activate the specific immune response and manufacture antibodies and memory cells
What are some examples of antigenic material used in vaccines?
-a harmless or attenuated (weakened) version of the pathogenic organism
-a dead pathogen
-a preparation of antigens from a pathogen
-a toxoid which is a harmless version of a toxin
What are the principles of herd vaccination?
-when a large amount of the population is immunised to reduce the spread of the pathogen
When is ring vaccination used?
-used when a new case of disease is reported
-all people who have been in contact with/ live close to the patient are vaccinated
What is an epidemic?
-a rapid spread of disease through a high proportion of the population
Antibodies can defend the body against pathogens in a number of ways.
Outline the mode of action of antibodies in defending the body against pathogens by describing the processes of neutralisation and agglutination
(4 marks)
Neutralisation:
-cover/ block binding site/antigen on pathogen
-bind to toxins
-(prevent binding/ entry to (host) cell)
Agglutination
-clump/bind together (many)pathogens
-(clump) too large to enter (host) cell/ cross membranes
-(increase likelihood of being consumed by (neutrophil/ macrophage) )
The term immunity is often used when describing how vaccines work.
In a piece of school homework a student wrote “Bacteria can evolve quickly and many are now immune to antibiotics.”
Explain why the student’s use of the word ‘immune’ was incorrect
(3 marks)
-bacteria do not have an immune system
-correct term is that bacteria are resistant
-bacteria are unicellular / only multicellular organisms have an immune response
Draw out the structure of an antibody and label it
Viruses do not use erythrocytes as host cells, whereas the malarial pathogen Plasmodium spends part of its life cycle inside erythrocytes
Suggest why
(2 marks)
Viruses
-need to use host cell’s machinery/ DNA for protein synthesis
Plasmodium
-plasmodium use it to complete its life cycle
(For plasmodium to use as a source of food)
A
A
Explain why booster vaccinations are needed
-as memory cells have reduced in number
