3.6 - immunology Flashcards
what’s a pathogenic organism
organism that has ability to cause damage to a host
what’s an infectious disease
a disease that can be transmitted between indiviudals
define carrier
infected individual that is asymptomatic but can spread the disease
what is the disease reservoir
environment (host) in which an infectious pathogen is found
define endemic
disease ever-present in an area
define epidemic
rapid rise in incidence of a communicable disease at a local or national level
what’s a pandemic
epidemic that occurs worldwide, affecting large number of individuals
define vaccination
deliberate exposure of an individual to non-pathogenic forms, antigens or products of pathogens to provide artificial active immunity
what’s an antibiotic
chemical or compound produced by a living organism that kills or prevents the growth of bacteria
what’s an antigen
chemical present on the surface of a cell that induces an immune repsonse
define antibodies
immunoglobulins produced by B-lymphocytes in response to a specific immune antigen, triggering an immune repsonse
what are antibiotic-resistant bacteria
bacteria that mutate to become resistant to an antibiotic, survive + reproduce v rapidly, passing on their antibiotic resistance
define vector
living or non-living agent that transmits pathogen between organisms
what’s a toxin
substance produced by pathogen that causes damage to host
what are antigenic types
organisms that possess same or similar antigens on their surface, e.g: strains of bacteria
how are antigenic types usually identified
using antibodies from serum
what’s a host
organism from which a pathogen or parasite obtains nutrients and/or shelter
examples of bacterial infections
- cholera
- tuberculosis
what’s cholera
disease caused by strains of gram negative bacterium, vibrio cholerae
toxins of which cause severe diarrhoea leading to dehydration
how is cholera spread
- fecal/oral transmission
- ingesting contaminated food/water
how is cholera treated
- rehydration
- antibiotics
what’s tuberculosis
bacterial disease, caused by mycobacterium tuberculosis + m. bovis
damages lymph nodes in lungs + neck, weakening immune system
how is tuberculosis transmitted
airborne droplet transmission
describe the methods of tuberculosis prevention + treatment
prevention - BCG vaccination of children
treatment - extensive course of antibitoics
examples of viral infections
- influenza
- smallpox
how is the influenza virus transmitted
- droplet infection
- contact w/ contaminated surfaces
what tissue is affected by influenza
upper respiratory tract
describe the symptoms of influenza
headache, coughing, sneezing, sore throat, vomiting, fever, muscular + joint pain
may cause secondary bacterial infections
how is influenza treated
- quarantine
- antiviral medication
- antibiotics treat secondary bacterial infections
- management of symptoms, eg: painkillers
what is smallpox
disease caused by virus variola major that affects skin + multiple other organs
how is smallpox spread
- droplet transmission
- bodily fluids
describe the symptoms of smallpox
headache, fever, + pockmarking of skin
describe how smallpox has been eradicated
due to successful vaccination program
what properties of smallpox made its eradication possible
- little variation in antigens
- low rate of antigenic mutation
- immunogenic nature of antigens
- no animal resevoir
example of protoctista infection
malaria
name the malarial parasite
plasmodium spp.
outline mode of transmission + infection of plasmodium spp. parasite
- female mosquito acts as vector when transferring saliva to another organism during feeding
- parasite reproduces asexually in red blood cells in liver, causing lysis
describe effects of malaria on infected individual
causes recurrent episode of fever + can be fatal
how is endemic malaria controlled
preventing mosquito bites - mosquito nets, insect repellent
controlling mosquito numbers - pesticides, chemical treatment of standing water + sewage, introduction of predators for mosquitos
drug treatment
what are viruses
non-living infectious agents that invade host cells + take over cell metabolism, replicating within them
outline the forms that the pathogenicity of viruses can take
- cell lysis
- cell transformation
- production of toxins
- immune system suppression
what’s cell lysis
- disruption of cell membranes, destroying the cell
- virions released
describe cell transformation
viruses can stimulate healthy cells to become cancerous
example of virus that suppresses immune system of host
HIV
state the 2 types of antibiotics
- bacteriostatic
- bactericidial
how do bacteriostatic antibiotic work
prevent bacteria growing by interfering w/ processes required for growth such as metabolism or DNA replication
what are bactericidal antibiotics
antibiotics that kill bacteria
what’s a narrow spectrum antibiotic
antibiotic only effective against narrow range of bacteria
what’s a broad spectrum antibiotic
antibiotic that targets wide range of bacteria
what are bacterial cell wall made up of
3D mesh of peptidoglycan (murein), polymer of amino acids + sugars
define gram positive bacteria
bacteria that have thick peptidoglycan wall + purple appearance following gram staining
define gram negative bacteria
bacteria that have thin peptidoglycan wall + outer lipopolysaccharide membrane + red appearance following gram staining
what type of antibiotic is penicillin
narrow spectrum antibiotic
describe how penicillin affects bacteria
- kills gram positive bacteria + damages gram negative bacteria
- prevents formation of cross links between molecules in peptidoglycan wall, so when osmotic changes occur, cell undergoes lysis
how does penicillin prevent formation of cross links in peptidoglycan wall
- transpeptidase catalyses formation of cros links in peptidoglycan wall
- penicillin is competitive inhibitor of transpeptidase
why doesn’t penicillin kill gram negative bacteria
gram negative don’t completely lose cell walls due to presence of outer lipopolysaccharide membrane
what type of antibiotic is tetracycline
broad spectrum antibiotic
describe effect of tetracycline on bacteria
- inhibits translation during protein synthesis
- competitive inhibitor of anticodon binding site on 30S ribosomal subunits, preventing formation of new proteins
why do antibiotics not affect viruses
viruses dont have metabolic pathways
why are some bacteria resistant to treatment by antibiotics
- random genetic mutation, often on plasmid, confers resistance, e.g: antigen shape changes
- these bacteria have selective advantage in presence of antibiotics, reproduce + pass allele for resistance to offspring
- directional selection results in resistant strain
what are natural barriers
defences always present + same for all organisms
outline the natural defences in the body that reduce risk of infection
skin - protective layer
skin flora - protection from harmful pathogens, compete w/ them for nutrients
blood clotting - seals wounds
lysozymes - tears, hydrolyse bacterial cell walls
hydrochloric acid - stomach, kills bacteria
mucous membranes - trap pathogen + may secret antimicrobial enzymes
phagocytosis - destroys pathogens
inflammation - localises + eliminates cause of injury
describe the specific immune response
- second line of défense against pathogens triggered by foreign antigens
- 2 types: humoral immune response + cell-mediated immune response
what are T-lymphocytes
lymphocytes that mature in thymus gland
what are B lymphocytes
lymphocytes produced in bone marrow + mature in spleen + lymph nodes
outline the process of cell-mediated repsonse
- complementary T helper lymphocytes bind to foreign antigens on antigen-presenting cell
- T cells undergo clonal expansion
- three main types of T lymphocytes produced:
- T effector cells
- T helper cells
- T memory cells
explain the role of antigen-presenting cells
- macrophage displays antigen from pathogen on its surface (after hydrolysis in phagocytosis)
- enhances recognition by T helper cells, which can’t directly interface w/ pathogens/antigens in body fluid
- secrete cytokines that are involved in stimulating specific immune repsonse
what are T effector cells
- T killer cells or cytotoxic T lymphocytes
- causes lysis of damaged or infected cells
describe the role of T helper cells
- regulate immune response through release of cytokines
- cytokines stimulate proliferation of B lymphocytes
describe the role of T memory cells
remain in blood + provide immunological memory
outline the process of the humoral repsonse
- complementary T helper lymphocytes bind to foreign antigens on antigen-present T cells
- cytokines released that stimulate clonal expansion of complementary B lymphocytes
- B lymphocytes differentiate into plasma cells
- plasma cells secrete antibodies w/ complementary variable region to antigen
- antibodies destroy pathogen
describe structure of an antibody
- y shaped
- 2 light chains bonded to 2 longer heavy chains
- 2 binding sites
- specific to particular antigen
compare the primary + secondary immune responses
primary - initial response when pathogen is first encountered, small number of antibodies produced slowly
secondary - pathogen encountered for second (third, fourth… etc) time, immunological memory gives rapid production of large number of antibodies
what’s happening during latent period of primary immune repsonse
- antigen presenting cells carrying out phagocytosis
- T helper cell detect antigens + secret cytokines
- proliferation + differentiation of specific B + T cells
define active immunity
resistance in organism that has developed through production of specific antibodies in response to pathogen
provides long lasting immunity as memory cells are produced
what are the 2 types of active immunity
natural - production of antibodies by immune system following infection
artificial - production o antibodies by immune system following exposure to weakened, attenuated or dead pathogen
example of artificial active immunity
vaccination
how do vaccinations that use antigens provide long lasting immunity
- antigens in vaccine trigger primary immune response w/out infection
- if pathogen encountered, secondary immune response destroys pathogen before symptoms develop
define passive immunity
resistance in organism acquired via transfer of antibodies
provides short term immunity as no memory cells produced
what are the 2 types of passive immunity
natural - immunity acquired by infant mammal when antibodies transferred though placenta + colostrum from mother
artificial - immunity acquired from administration of specific antibodies from another organsim
example of artificial passive immunity
treatment of rabies
how do vaccinations that use antibodies provide short term immunity
- antibodies give rapid protection against harmful microorganism
- allows time for development of active immune response
describe the different levels of effectiveness of vaccination programmes against different diseases
- single round of vaccination protects against pathogens that have low level of antigenic variation/mutation, e.g: rubella
- repeated vaccinations used against pathogens that have various antigenic types + mutate frequently, e.g: influenza
outline the ethical considerations that must be considered when designing vaccination programmes
- cost of developing vaccine
- effectiveness of vaccine
- rights of individual vs rights of entire population to be protected
- possible side effects
- religious concerns
- testing on animals + unaffected individuals
