lecture 9 Flashcards
immunology challenges faced by the immune system structure of the immune system
challenges faced by the immune system – pathogens vary
it has to protect against a wide variety of pathogens like viruses bacteria fungi protozoa and parasitic worms
pathogens vary considerably in size location and in biochemical composition
what are the 4 major classes of pathogens that the immune system protects against
- extracellular pathogens: bacteria, parasites, fungi
- intracellular pathogens like bacteria and parasites
- intracellular pathogens like viruses
- extracellular pathogens like parasitic worms
define serotype
a variation of the bacteria that can be recognised by specific antibodies
extracellular pathogens examples (4)
- streptococcus pneumoniae is a gram-positive bacterium that causes pneumonia
it has more than 90 different stereotypes - clostridium tetani is a gram-positive spore-forming bacterium that causes tetanus
sports are extremely Hardy and resistant to heat and antiseptics
it produces a potent biological toxin called tetanospasmin, which one reaches the ends of motor neurones interferes with the neurotransmitter release and causes muscle spasms
a typical dose of tetanospasmin is too small to provoke an immune response - trypanosoma brucei is a protozoan that causes sleeping sickness
it is carried by tsetse flies and acquires a dense layer of glycoproteins that continually change allowing the parasite to dodge an attack from the hosts immune system
is causes drowsiness sleepiness insomnia anxiety and weakness - pneumocystis carinii is a yeast like fungus that causes pneumocystis pneumonia
intracellular pathogens bacteria/parasites examples (3)
mycobacterium leprae is a gram positive bacteria that infects macrophages and schwann cells (causes leprosy)
leishmania donovani is a protozoan that infect macrophages causes (leishmaniasis)
plasmodium falciparum is a protozoan that infected recites and causes malaria
intracellular pathogens viruses examples (3)
variola causes smallpox
influenza causes the flu
varicella causes chickenpox
it is always intracellular because the use of ribosomes to make proteins which means they initially had proteins that look like ours which makes it harder for immune system to distinguish between them
extracellular pathogens parasitic worms (2)
ascaris is a nematode roundworm and causes ascariasis
schistosoma is a trematodes platyhelminth flatworm which causes schistosomiasis
challenges faced by the immune system – rapid viral evolution
rapid viral evolution is a virulence strategy which means it’s a way that viruses subvert and avoid our immune system by making brand new forms
pathogens can mutate very quickly sore immune system can’t recognise them and they become resistant to antibodies
rapid evolution of HIV by mutations
HIV has an RNA genome associated with an RNA replicase and the mutation rate during copying is very fast. but it is very easy to spot because of its characteristic shape of its capsule.
the flu evolves rapidly by recombination of its RNA segments. Haemagglutinin and Neuraminidase are surface spikes which we can recognise
describe the steps of the Spanish flu epidemic in 1918
at the end of World War 1 people died of cytokine storms which is an over responsive immune system attack
flu is a pathogen of aquatic birds (they get it in their guts we get it in our lungs)
recombination events triggered the Asian flu epidemic when 3 rnas transferred from bird flu to human flu
recombination events triggered the Hong Kong flu but fortunately this had a low death rate and it’s innate response is very quick
it started as H1N1 bird flu 8 RNAs transferred became H1N1 human flu 3 RNAs transferred from H2N2 bird flu became H2N2 human flu 2 RNAs transferred from H3N? bird flu became H3N2 human flu
challenges faced by the immune system – antigenic variation/shift as a virulence strategy
during an initial infection the Host immune system generates an immune response that normally protects against persistent or repeat infections
some pathogens can alter the surface proteins to avoid host immune responses
describe the life cycle of the human malaria parasite plasmodium falciparum
The mosquito bit an infected human Mosquito’s gametes are infected Fuse to form zygotes Invade the gut Invade the salivary glands Forms sporozoites
Bites human Sporo infects humans Replication in liver Infects RBC Gametocytes are formed in the blood
challenges faced by the immune system – the exposure to pathogens is common
this means that the immune response must have a memory
the primary response to a new challenge takes 10 days
the secondary response upon re-exposure it’s much more powerful but still takes 6 days to peak
memory improves the secondary response
this is how vaccines work to give us a stronger and faster response
challenges faced by the immune system – pathogens grow and divide quickly
pathogens grow and divide quickly so in immune response must be rapid
the primary response in the secondary response or to slow
we therefore rely on our innate immunity during the first few critical hours after exposure to new pathogen
challenges faced by the immune system – recognition of self, non self and altered self
the immune system has to distinguish non-self from self
typical non-self: bacterial cell wall structures protein and peptide structures sequences from pathogens yeast carbohydrates pathogen DNA viral antigens on host cells
the immune system also has to process altered self such as malignant cells, apoptotic cells, oxidized proteins
challenges faced by the immune system – immune responses have to be tissue-specific
the composition of the immune system constituents are tailored to specific tissues
different tissues display different immune responses
our brain uses entirely innate responses
the blood brain barrier separates circulating blood from the brain extracellular fluid to form an obstacle to macromolecules of the adaptive system like antibodies
