Disease and the immune system Flashcards
Name 4 groups of pathogen that can cause disease?
- bacteria
- fungi
- protoctista
- viruses
How does myobacterium tuberculosis cause disease?
- triggers inflammatory response by infecting phagocytes in the lungs
- infected phagocytes are sealed in waxy-coated tubercules so bacteria remains dormant (first infection is symptomless)
- if another factor weakens immune system bacteria becomes active and destroys lung tissue
How does HIV result in the symptoms of AIDS?
- attachment proteins bind to complementary CD4 receptors on TH cells
- HIV particles replicate in TH cells killing/ damaging
- AIDS develop when there are few TH cells for the immune systems function
- individuals can’t destroy other pathogens and suffer from secondary infections/ diseases
How does tobacco mosaic virus cause disease?
- affects plants (transmitted via infected cell sap)
- contains ssRNA which is transcribed by host cells to assemble new virions
- virions enter other cells through plasmodesmata then enter xylem + phloem
- causes stunted growth and mottled leaves
What causes malaria?
- female mosquitoes act as a vector for plasmodium protoctista
- parasite produces asexually in RBC in the liver causing lysis
What causes potato/ tomato blight and ring rot?
Blight = protoctista mainly transmitted via spores
Ring rot = protoctista mainly transmitted by planting infected seeds
How are communicable pathogens transmitted directly?
- inhalation (droplet infection)
- skin to skin contact/ fluid exchange
- penetrating of skin through enzymes and wounds
How are communicable pathogens transmitted indirectly?
- contaminated food and drink
- via a vector
- spores
How do living conditions affect disease transmission?
- overcrowding increases direct transmission
- climate determines which organisms can survive
- social factors influencing how quickly people are treated
Name 4 physical barriers the pathogen entry in plants?
- cellulose cell walls
-lignified layers
- waxy upper cuticle
- old vascular tissue blocking spread within the plant
Describe 2 mechanical responses to infection in plants?
- guard cells close stomata
- thick polysaccharide callose is produced and deposited between the cell wall and plasma membrane limiting spread
Name 5 barriers to animal infections?
- tough keratin skin layer
- blood clotting preventing pathogen entering body
- hydrochloric acid in stomach killing bacteria
- gut and skin bacteria compete with pathogen
- mucus membranes trap pathogen and secrete enzymes
What are expulsive reflexes?
Body’s attempt to force foreign substances out
- sneezing due to irritation of mucous membranes in nostrils
- coughing due to irritation ciliated epithelium in respiratory tract
Name 4 ways the non specific immune system responds to infection?
- inflammation
- phagocytosis
- digestive action of lysosomes
- production of antiviral agent
Outline the process of inflammation?
1) damaged vessels release histamine causing vasodilation
2) blood flow and permeability of blood vessels increases
3) WBC and plasma move into infected tissue
How does blood clotting occur?
1) blood platelets plug and release chemicals that enhance clotting (thromboplastin)
2) prothrombin changes into thrombin (it’s active form)
3) fibrinogen changes into insoluble fibrin which covers the wound
Name two types of WBC involved in phagocytosis?
- neutrophil
- macrophages
How does phagocytosis destroy a pathogen?
- phagocyte moves towards pathogen which may have been marked by opsonins
- phagocyte engulfs pathogen via endocytosis to form a phagosome
- phagosome fuses with lysosome (phagolysosome)
- lysozyme digests pathogen
- phagocyte absorb the products from pathogen hydrolysis
Explain the role of antigen-presenting cells?
- macrophage displays antigen from pathogen on it’s surface
- enhances recognition by Th cells which can’t directly interface with pathogens/ antigens in body fluid
- secrete cytokines involved in stimulating specific immune response
What are lysozymes?
Digestive enzymes found in lysosomes as well as many secretions. Damage bacteria cell walls causing osmotic lysis
Name the 2 types of specific immune responce?
- cell mediated
- humoral
Outline the process of cell mediated responce?
- complementary Th lymphocytes bind to foreign antigens on APC
- cell signalling via secretion of interleukins stimulates…
a) clonal expansion of complementary Th cells (rapid mitosis) becoming memory cells or triggering humeral responce
b) clonal expansion of cytotoxic T cells secreting perforin enzyme to destroy infected cells
Outline the process of humeral responce?
- complementary Th lymphocytes bind to foreign antigen on antigen presenting cells
- release cytokines that stimulate clonal expansion (rapid mitosis) of complementary B lymphocytes
- B cells differentiate into plasma cells
- plasma cells secrete antibodies with complementary variable region to antigen
Describe the structure and function of B lymphocytes?
- differentiate into plasma cells to secrete antibodies to destroy the pathogen
- remain in barrow until mature
Describe the structure and function of T lymphocytes?
T helper = secrete cytokine
T killer = secrete perforin
T regulator = suppress other immune cells to prevent autoimmune disease
What is an antibody?
a protein secreted by plasma cells
Describe the structure of an antibody?
Quaternary structure = 2 ‘light chains’ held by disulfide bridges with 2 ‘longer’ heavy chains
Binding sites = on variable regions of light chains have specific tertiary structure complementary to antigen
Constant region = rest of antibody
How do antibodies lead to the destruction of pathogens?
- agglutinins form antigen antibody complexes to enhance phagocytosis
- activation of complement
- opsonins mark microbes for phagocytes
- antitoxins make toxins insoluble via precipitation/ neutralisation
What are memory cells?
- specialised Th/B cells produced from primary immune response
- remain in low levels in the blood
can divide very rapidly by mitosis if organism encounters the same pathogen again
Contrast the primary and secondary responce?
- secondary responce has faster rate of antibody production than primary
- secondary responce has a shorter time lag between exposure and antibody production than primary
- secondary responce has higher antibody concentration than primary
- antibody levels remain higher after secondary responce than primary
- pathogen usually destroyed before any symptoms in secondary responce not primary
What is passive immunity?
immunity required through transfer of antibodies from one individual to another
What is active immunity?
immunity required through production of antibodies in responce to infection or through vaccination
What is the difference between active and passive immunity?
- both involve antibodies and can be natural and artificial
- passive is immediate whereas active’s a time lag
- passive has antibodies from an external source whereas active is from lymphocytes (antibody)
- passive has no direct contact with an antigen whereas active needs direct contact
- passive has no memory cells and is short term whereas active has memory cells and is long term
What is natural immunity?
natural immunity develops after an infection resulting from body’s responce to an antigen
What is artificial immunity?
when the body is given immunity to a disease by vaccination
What are examples of passive and active immunity?
Passive natural = antibodies in breast milk
Passive artificial = anti venom needle injection
Active natural = humoral responce to infection
Active artificial = vaccination
What is an autoimmune disease?
Immune system produces antibodies against it’s own tissue
Give 2 examples of autoimmune diseases?
Rheumatoid arthritis = immune system targets synovial lined joints causing inflammation
Lupus = results in inflammation throughout the body
Define endemic?
disease occurring routinely in a geographical area
Explain the principle of vaccination?
- vaccine contains dead/ inactive for of pathogen
- triggers primary immune responce
- memory cells are produced and remain in the bloodstream so secondary responce is rapid producing higher antibody concentrations
- pathogen is destroyed before causing symptoms
Define pandemic?
temporary rapid increase in incidence of disease in a geographical area
What role do vaccines play in preventing endemics?
- vaccinating 80-90% of population reduces available carriers of pathogen (herd immunity)
- vaccinating close contacts of infected individuals limits spread
What are possible natural sources of medicine?
- microorganisms
- fungi (e.g penecillin)
- plants (e.g foxglove)
What are the benefits of using antibodies to treat bacterial infections?
- reduces population of bacteria colony
- inhibit formation of nucleic acids (growth)
- prevent formation of peptidoglycan cross-links (osmotic lysis)
What are the risks of using antibiotics to treat bacterial infections?
- overuse increasing resistant strains of bacteria
- difficult to treat antibiotic resistant strains of bacteria
