4.1 Communicable Diseases, Disease Prevention And The Immune System Flashcards
What organisms are pathogens?
Bacteria, viruses, fungi, protoctista.
What communicable diseases are caused by bacteria?
Ring rot (potatoes and tomatoes)
Tuberculosis
Bacterial meningitis
What communicable diseases are caused by viruses?
Tobacco mosaic virus
HIV/AIDS
Influenza
What communicable diseases are caused by fungi?
Black Sigatoka (bananas)
Ring worm
Athletes foot
What communicable diseases are caused by protoctista?
Malaria
Potato/tomato blight
Examples of communicable disease transmission in animals
Vectors (animals/water)
Fomites (inanimate objects)
Direct contact
Inoculation (break in skin)
Ingestion
Droplet infection
Factors affecting transmission of communicable diseases in animals.
Overcrowding
Poor nutrition
Compromised immune system
Poor waste disposal
Climate change
Culture/infrastructure
Socioeconomic factors
Examples of transmission of communicable disease in plants
Direct contact of healthy plant with any part of a diseased plant
Soil contamination (infected plants leave spores or pathogens in soil)
Vectors (wind, water, animals, humans)
Factors affecting transmission of communicable diseases in plants.
Planting varieties of crops susceptible to disease
Over-crowding
Poor mineral nutrition
Damp, warm conditions
Climate change
What is an example of a physical defence in plants and how does it work?
High production levels of callose.
Minutes following an attack, it’s synthesised and deposited between cell walls + cell membrane in cells next to infected cells.
Act as barrier and prevent pathogens spreading to other cells.
Lignin added, making barrier thicker + stronger
Sieve plates blocked, sealing infected region.
Deposited into plasmodesmata.
List examples of chemical defences in plants.
Insect repellents
Insecticides
Antibacterial compounds (antibiotics)
Antifungal compounds
Anti-oomycetes
General toxins
What are the body’s barriers to entry of pathogens as part of non-specific defences?
Skin
Body tracts lined by mucous membranes that secrete sticky mucus (which has phagocytes) and contains lysozymes
Lysozymes in tears and urine
Acid in stomach
Expulsive reflexes (coughing/sneezing, vomiting/diarrhoea)
Non-specific defences in animals, blood clotting, explain
Blood clotting and wound repair
- thromboplastin, enzyme that triggers cascade of reactions, forms blood clot
-serotonin makes smooth muscle in walls of blood vessels contract, narrow and reduce supply of blood
- clot dries, collagen fibres deposited to give new tissue strength
How do fevers act as a non-specific defence mechanism in animals?
Cytokines stimulate hypothalamus and temperature goes up
Higher temperatures inhibit pathogen reproduction
Specific immune system works faster at higher temperatures
How does phagocytosis act as a non-specific defence mechanism in animals?
Pathogens produce chemicals that attract phagocytes, they recognise non-human proteins on the pathogen
Phagocyte engulfs pathogen and encloses it in phagosome
Phagosome combines with lysosome to form phagolysosome
Enzymes from lysosome digest and destroy pathogen.
Macrophages digest the pathogen and combine antigens with glycoproteins called the major histocompatibility complex .
MHC complex moves antigens to macrophages’s surface membrane, becomes an antigen-presenting cell.
How are cytokines part of the non-specific animal defence?
Phagocytes that have engulfed a pathogen produce them
Act as cell-signalling molecules, inform phagocytes the body is under attack, stimulate them to move to site of infection
Increase body temp, stimulate specific immune system
How are opsonins part of the non-specific animal defence?
Bind to pathogens, tag them to be easily recognised by phagocytes
Receptors on cell membranes that bind to common opsonins
Phagocyte engulfs opsonins then pathogen
Structure of antibodies
Y-shaped glycoproteins, immunoglobulins
2 identical long polypeptide chains, heavy chains
2 shorter identical chains, light chains
Chains held together by disulfide bridges
Disulfide bridges within the polypeptide chains, holding them in shape.
Variable region, binding site
Constant region, rest of it
How do antibodies defend the body?
Antibody of antigen-antibody complex acts as an opsonin so it’s easily engulfed and digested by phagocytes
Most pathogens can’t invade host cells once part of complex
Act as agglutinins, cause pathogens carrying the complexes to clump together
Prevents spreading through body, easier for phagocytes to engulf number of pathogens at the same time
Act as anti-toxins, bind to toxins produce by pathogens, makes them harmless
How do T helper cells contribute to the specific immune response?
Have CD4 receptors, bind to antigens on APCs
Produce interleukins, type of cytokine, stimulate activity of B cells, increases antibody production, stimulates production of other types of T cells, attracts and stimulates macrophages to ingest pathogens w complexes
How do T killer cells contribute to the specific immune response?
Destroy the pathogen carrying the antigen
Produce perforin, kills pathogen by making holes in cell membrane so its freely permeable
How do T memory cells contribute to the specific immune response?
Part of the immunological memory
If they meet an antigen a second time, divide rapidly to form huge number of clones of T killer cells
How do T regulator cells contribute to the specific immune response?
Suppress the immune system, acting to control and regulate it
Once a pathogen has been eliminated, they make sure the body recognises self antigens and no autoimmune response occurs
How do plasma cells contribute to the specific immune response?
Produce antibodies to particular antigen, release them into circulation
Only lives for few days but produces around 2000 antibodies per second
How do B effector cells contribute to the specific immune response?
Divide to form plasma cell clones
How do B memory cells contribute to the specific immune response?
Live for a long time, provide immunological memory
Programmed to remember specific antigen and enable body to have rapid response when pathogen carrying that antigen is encountered again
What is cell mediated immunity?
T lymphocytes respond to cells of organism that have been changed (virus infection, antigen processing, mutation)
Describe the process of cell mediated immunity
Macrophages engulf and digest pathogens, become APCs
Receptors on some of T helpers fit antigens, become activated and produce interleukins, stimulate more T cells to divide rapidly by mitosis, clones of activated T helpers, carry right antigen to bind to particular pathogen
Cloned T cells either
- develop into T memory cells
- produce interleukins that stimulate phagocytosis
-produce interleukins that stimulate B cells to divide
-develop into T killer cells and destroy infected cells
What is humoral immunity?
Body responds to antigens found outside cells (bacteria, fungi, APCs)
Describe the process of humoral immunity (primary response)
B cell with complementary antibody binds to pathogen, engulfs it and processes it to be APC
Activated T helper cells bind to APC, clonal selection, B cell with correct antibody selected for cloning
Interleukins produced activate the B cells
B cell divides by mitosis, clonal expansion, clones of plasma cells and B memory cells
Plasma cells produce antibodies, bind to antigens, disable them or act as opsonins/agglutinins
Describe the process of humoral immunity (secondary response)
Some cloned B cells develop into B memory cells
If body is infected with same pathogen again, B memory cells divide to form plasma cell clones
Produce correct antibody and wipe out pathogen before it can cause symptoms of disease
Non-specific defences in animals, inflammation, explain
Inflammatory response
- mast cells activated in damaged tissue, release histamines and cytokines
- histamines make blood vessels dilate makes it hotter so pathogens can’t reproduce
- histamines make walls more leaky, tissue fluid forced out
- cytokines attract phagocytes
