4.1 Communicable diseases, disease prevention and the immune system Flashcards
bacteria facts
smaller than eukaryotic cells
reproduce rapidly (20 minutes in optimal conditions)
damage cells through release of toxins
e.g. tuberculosis, meningitis, ring rot (potatoes, tomatoes)
fungi facts
often live in skin
hyphae form mycelium
reproductive hyphae grow into skin and releases pores (redness to skin)
live in vascular tissue in plants to gain nutrients
hyphae release extra cellular digestive enzymes to break down cellulose (decays plant)
e.g. black sigatoka (plants), ringworm (cattle), athlete’s foot
protoctista facts
enter host cell and feed on contents of cell
malaria parasite Plasmodium has immature forms that feed on haemoglobin
e.g. malaria, potato/tomato later blight
viruses facts
invades cell and rakes over genetic machinery and other organelles
causes cells to manufacture more copies of virus
host cell eventually bursts, releasing new viruses to invade new host cells
e.g. HIV, influenza (animals), tobacco mosaic virus (plants)
direct transmission definition
passing a pathogen from host to new host with no intermediary
indirect transmission definition
passing a pathogen from host to new host, via a vector
transmission definition
passing a pathogen from an infected to an uninflected individual
vector definition
organism that carries a pathogen from one host to another
means of transmission
direct physical contact (touching infected people or contaminated surfaces)
faecal-oral transmission (intaking contaminated food or water)
droplet infection (pathogen carried in tiny water droplets in air)
spores (resistant stage of pathogen carried in air or reside on surfaces or soil)
social factors of transmission
overcrowding
poor ventilation
poor health (person who has HIV/AIDS more likely to contract other diseases)
poor diet
homelessness
living with people who migrated from areas where a disease is more common
factors affecting direct physical contact (transmission)
hygiene (wash hands regularly) keeping surfaces clean clean and disinfect cuts and abrasions sterilise surgical instruments use condoms during intercourse
factors affecting faecal-oral transmission
treatment of drinking water
thoroughly wash food (with treated water)
prepare and cook food carefully
factors affecting droplet infection (transmission)
catch it (cover mouth when coughing or sneezing) bin it - kill it (use and dispose tissue)
factors affecting spore transmission
use mask
wash hands after being in contact with soil
indirect transmission of malaria method
gametes of plasmodium in person with malaria
female Anopheles mosquito sucks blood
Plasmodium develops and migrates to mosquito’s salivary glands
uninfected person is bitten
Plasmodium migrates to liver then blood
cycle starts again
direct transmission of plant pathogens
pathogens in soil enter roots of plant (especially if damaged)
fungi produce spores may be carried by wind
may infect vascular tissue
distributed back to soil when leaves shed
may enter fruit and distributed with seeds (so offspring also afflicted)
indirect transmission of plant pathogens
pathogen attaches to insects (vector) when they attack infected plant
they attack uninfected plants and transmit disease
how climate affects disease
grow and reproduce quicker in warm, moist conditions
more common with greater variety in warmer climates
pathogens damaged or killed in cold (winter) weather and stunts rate of reproduction
passive defence definition
defence present before infection and prevents entry and spread of pathogen in organism
physical defences in plants
cellulose cell wall (physical barrier)
lignin thickening of cell walls (waterproof and almost completely indigestible)
waxy cuticle (prevents water that may contain pathogens collecting on cell surface)
bark (physical barrier)
stomatal closure (blocks potential point of entry for pathogen)
callose (large polysaccharide deposited in sieve tube to prevent spread of pathogen around plant)
tylose formation (balloon-like swelling that plugs xylem vessels when full to block spread of pathogens through xylem)
chemical defences in plants
plant tissue contain variety of chemicals with with anti-pathogenic properties
some may be present before infection (terpene in tyloses, tannins in bark)
most are in active defence as chemical production requires a lot of energy
active defence definition
initiated when pathogen is detected inside the organism
active defences in plants
cell walls thicken with more cellulose
deposition
callose deposited between plant cell wall and cell membrane (impedes cellular penetration)
also strengthens cell walls and blocks plasmodesmata
oxidative bursts (highly reactive oxygen molecules, damages cells of invading organisms)
increase production of chemicals
necrosis - deliberate death of infected cells to stop spread
primary defence definition
prevents pathogens entering the body / bloodstream
inflammation definition
swelling and redness of tissue caused by infection
blood clot formation
blood vessel is damaged
platelets bind to exposed collagen to form temporary platelet plug
platelets release clotting factor (activates enzyme cascade)
enzyme cascade causes fibrinogen to form insoluble fibres (attaches to plug)
RBCs trapped (forms clot, dries to form scab)
scab pulls skin together
collagen deposited under skin
stem cells in epidermis divide and differentiate to from new skin cells at edge of cut
new blood vessels form
repair complete when edges of cut drawn together
mucous membrane definition
specialised epithelial tissue covered by mucus
expulsive reflexes
coughing, sneezing, vomiting
irritation caused by presence of microorganisms or their toxins
causes sudden expulsion of air
carries microorganisms causing irritation
inflammation method
mast cells detect microbes and release histamines
causes vasodilation in arterioles (makes capillaries more permeable so WBCs can leave into tissue fluid)
more tissue fluid formed (more plasma leaves)
causes oedema (swelling)
tissue fluid can drain into lymph vessels (pathogens more likely to come into contact with lymphocytes, causing specific immune response)
primary defences in humans examples
skin (physical barrier) blood clotting and skin repair mucous membranes coughing and sneezing (expulsion reflexes) inflammation enzymes in tear fluid (lysozyme) mucous plug in cervix maintaining acidic conditions in vagina
secondary defence definition
combats pathogens that have already entered body/bloodstream
first line of secondary defence
phagocytes (specialised cells in blood and tissue fluid that engulf and digest pathogens)
neutrophil facts
leukocyte / phagocyte travel around body in blood often squeezed into tissue fluid short-lived most common phagocyte (40-60%) die soon after digesting few pathogens dead neutrophils can collect to form pus
neutrophil distinguishable features
multi-lobed nucleus
receptors (complementary to antigen)
more lysozymes
phagocytosis method
receptor on phagocyte’s cell surface membrane binds to antigen on pathogen’s cell cell surface membrane
pathogen engulfed by endocytosis (pseudopodium surround it first)
produces phagosome
lysozymes fuse with phagosome (releasing lysins into it)
digested into amino acids
products absorbed into cytoplasm by diffusion
looking at blood smears
RBCs = red, biconcave disc monocytes = largest WBC, large kidney-shaped nucleus neutrophil = multilobed nucleus lymphocytes = smaller, nucleus almost fills cells
macrophage facts
travel in blood as monocytes
produced in bone marrow
mature in lymph nodes
when engulfing pathogen, saves its antigen and moves it to special protein complex in surface of cell
becomes antigen-presenting cell
special protein complex makes sure antigen-presenting cell isn’t attacked by other phagocytes
antigen presentation (active immunity)
antigen-presenting cell moved around body
comes in contact its specific cells (that can activate full immune response - T and B lymphocytes)
only one T and B lymphocytes
antigen-presenting cells increase chances antigen will come in contact with them
specific immune response
activation of B and T cells = clonal selection
initiates complex series of events that leads to production of antibodies and memory cells (for long-term immunity)
series of events coordinated by cytokines (hormone-like chemicals)
stimulates differentiation and activity of macrophages, clonal expansion (B and T cells)
specialised T cells
T helper cell: releases cytokines (stimulates clonal expansion of B cells)
T killer cell: kills host-body cells displaying foreign antigen
T memory cell: stays in blood stream for long term immunity
T regulator cell: shuts down immune response after pathogen successfully removed
specialised B cell
plasma cell: circulate in blood, making and releasing antibodies
B memory cell: remain in body for immunological memory
cell signalling definition
communication between cells
cell signalling in immune response
antigens on pathogens state they are foreign to body cells
infected cells with foreign antigen on plasma membrane communicate to lymphocytes for clonal selection and T killer cells they need to be killed
macrophages ingest and incorporate antigens on plasma membrane (antigen-presenting cell), for lymphocytes for clonal selection
T helper cells release cytokines (stimulates B cells for clonal expansion)
autoimmune disease definition
immune system attacks part of the body
examples of autoimmune diseases
lupus - swelling and pain (antibodies attack nuclei of cells)
arthritis - painful inflammation (antibodies attack membranes around joint)
where B and T lymphocytes made and mature
both made in bone marrow
B lymphocytes mature in bone marrow
T lymphocytes mature in thymus
clonal selection method
foreign antigen detected by T and B lymphocytes with complementary shape receptors
helped by antigen-presenting cells, infected cells with foreign antigen on membrane
antibody definition
immunoglobulins, complex proteins they bind to specific antigens, released by plasma cells
structure of antibody
heavy and light polypeptide chains held together by disulphide bond hinge region (for flexibility so can attach to multiple antigens) variable region (specific shape complimentary to specific antigen) constant region (same in all antibodies, may have site to bind to phagocytic cells)
types of antibodies
opsonins
agglutinins
antitoxins
opsonin role
opsonisation
bind to antigens on pathogen
act as binding site for phagocytes (easier phagocytosis)
may bind to specific antigens with specific role (neutralisation)
some may stick to molecule not present in host cell e.g. peptidoglycan
agglutinin role
agglutination bind to multiple pathogens (cross link) clumps pathogen together become too big to enter host cell more likely to encounter and be engulfed by phagocyte
antitoxin role
binds to toxic molecules released by pathogen, renders them useless
primary vs secondary immune response
primary:
time delay to trigger immune response after first infection
no memory cells (slower and less antibody production)
secondary:
antibody production immediate (faster clonal selection and expansion due to memory lymphocytes)
more and faster antibody production
why new drugs need to be developed
new drugs needed to combat new diseases
new antibiotics needed due to antibacterial resistance
different medications to suit different people (e.g. allergies or lifestyle choices)
maintain biodiversity (new sources of drugs)
how drugs are made
microbes and some plants produce compounds with medicinal properties
personalised medicine
possible to screen genome of plants / microorganisms to identify how medicinal compounds produced
eventually able to sequence genes from individuals and develop specific drugs for each person
synthetic biology
development of new molecules that mimic biological molecules e.g. enzymes
antibiotic definition
used to treat / avoid bacterial infection
benefits of antibiotics
prevents infection after surgery (reduces complication / death rates)
treat infections body can’t “fight off”
risks of antibiotics
overuse / misuse allows bacterial strains to become resistant to antibiotics (reduces effectiveness)
types of immunity
artificial
natural
passive
active
active immunity definition
through activities of person’s own immune system
more long term
passive immunity definition
without activation of lymphocytes (antibodies made by another person)
eventually lost
artificial immunity definition
gained by deliberate exposure to antigens or antibodies
natural immunity definition
gained in normal cause of living
example of natural active immunity
result of infection
example of natural passive immunity
antibodies provided via placenta or breast milk
example of artificial active immunity
infection of weakened version of disease / antigenic material
example of artificial passive immunity
injection of antibodies
vaccination definition
deliberate exposure to antigenic material, activating immune system to make immune response and provide immunity (due to memory lymphocytes in bloodstream)
epidemic definition
disease spread quickly, affecting large proportion of population
pandemic definition
disease spread worldwide over many countries and continents
examples of antigenic material
harmless / dead version of disease
microbes with very similar-shaped antigens
antigens themselves
herd vaccination
using vaccine to provide immunity to (almost) all of population at risk
stops infection spreading
ring vaccination
vaccinate all people living with or near victim
requires people to report victims
contains spread within ring
people who need to be immunised
elderly/young children (weak immune system / little time to build up immunity to many diseases)
people with HIV/AIDS (weak immune system, can’t produce many antibodies themselves)
pregnant women (foetus underdeveloped immune system)
health workers/people living near outbreak (higher risk of getting disease)
people with chronic diseases / had chemotherapy/transplant (already in poor health, can’t withstand further disease)
why people choose to not get immunised
too busy / lazy to go to doctors media scare stories concerned about side effects allergic to vaccine dear of needles religious reasons cost of vaccine too expensive
why government want people to be vaccinated aside health benefits
prevention of disease can minimise sick days off work (minimises damage to economy)
costs less to immunise than treat people
health service may not be able to cope if large people became infected
why elderly et al. encouraged to get vaccine for influenza every year
vaccine changed every year
different strains each year
new strains have different antigens
old antibodies not complementary to new antigen
new vaccine encourage new antibodies to be made
