Lecture 9: Challenges faced by the immune system and overview Flashcards
Tuesday 29th October 2024
What are the different types of pathogen?
Bacteria, viruses, protozoa, parasites, fungi
What do pathogens vary in?
size, location (intracellular/extracellular), biochemical composition
Order pathogens in size order
Viruses
Intracellular bacteria
Extracellular bacteria, archaea, protozoa
Fungi
Parasites
Name 3 extracellular pathogens
Streptococcus pneumonia
Clostridium tetani
Pneumocystis carinii
What type of pathogen is Streptococcus pneumonia
Gram positive bacteria
How many different serotypes are there of Streptococcus pneumonia?
More than 90
What sorts of conditions can Streptococcus pneumonia cause?
acute sinusitis, otitis media, meningitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis … as well as pneumonia.
is it true that Streptococcus pneumonia is part of the normal upper respiratory tract flora but can become pathogenic under the right conditions (e.g., immunosuppression)?
Yes
What does Streptococcus pneumonia compete with?
Haemophilus influenzae (a Gram negative bacterium that can also cause pneumonia and meningitis)
How does Streptococcus pneumonia compete with Haemophilus influenzae?
by attacking it with hydrogen peroxide.
How does Haemophilus influenzae respond to attack from Streptococcus pneumonia ?
by signalling to our immune system to attack the S. pneumoniae
What type of pathogen is Clostridium Tetani?
Gram-positive, spore-forming anaerobic bacterium.
Describe the spores of Clostridium Tetani
extremely hardy, resistant to heat and most antiseptics, widely distributed in manured soils, on human skin and in contaminated heroin.
What biological toxin is produced by Clostridium Tetani?
tetanospasmin
What disease does Clostridium Tetani cause?
Tetanus
What are the features of tetanus?
- risus sardonicus (a rigid smile),
- trismus (commonly known as “lock-jaw”),
- opisthotonus (rigid, arched back).
In what percentage of cases is tetanus fatal in?
Around 40% of cases
Is it true that a typical dose of tetanospasmin is too small to provoke an immune response?
Yes
Give 3 examples of extracellular pathogens
Ascaris
Schistosoma
Trypanosoma brucei
What type of pathogen is Ascaris?
Nematode roundworm parasite
What disease is caused by Ascaris?
Ascariasis
What type of pathogen is Schistosoma?
Trematode platyhelminth flatworm parasite
Is it true that the pathogens in Ascariasis bury their way through the intestines and make their way up the lungs?
Yes
What type of pathogen is Pneumocystis carinii?
Yeast- like fungus
What type of disease is caused by Pneumocystis carinii?
Pneumocystis pneumonia
What is the main type of ilness caused by Streptococcus pneumonia?
Pneumonia
What disease does Schistosoma cause?
Schistosomiasis
What type of pathogen is Trypanosoma brucei?
A protozoa
What disease does Trypanosoma brucei cause?
Sleeping sickness
What is the protozoan Trypanosoma brucei carried on?
Tsetse flies.
Why is it difficult for our immune system to attach to the epithelial cells of protozoan Tsetse flies?
because they acquire a dense layer of glycoproteins that continually change, allowing the parasite to dodge
an attack from the host’s immune system.
What do the general symptoms of african sleeping sickness include?
Drowsiness, sleepiness (may be uncontrollable)
Insomnia at night
Anxiety, mood changes
Fever, headache, sweating
Swollen lymph nodes all over the body
Weakness
Without treatment, death may occur within 6 months from cardiac failure
Name some intracellular pathogens
Mycobacterium leprae
Leishmania donovani
Plasmodium falciparum
Variola
Influenza
Varicella
What type of pathogen is variola?
Virus
What disease does variola cause?
Smallpox
What type of pathogen is influenza?
Virus
what disease does influenza cause ?
The flu
What type of pathogen is varicella?
Virus
What disease does varicella cause ?
Chickenpox
What type of pathogen is Mycobacterium leprae?
Gram positive bacterium
What cells does Mycobacterium leprae
infect?
Infects macrophages and Schwann cells
What disease does Mycobacterium leprae
cause?
Leprosy
What type of pathogen is Leishmania donovani?
Protozoan
What cells does Leishmania donovani infect?
macrophages
what disease does Leishmania donovani
cause?
Leishmaniasis
What type of pathogen is Plasmodium falciparum?
Protozoan
What cells does plasmodium falciparum infect?
erythrocytes
What disease does plasmodium falciparum cause?
Malaria
Is it true that viruses evolve and mutate very quickly?
Yes
What 2 things can viruses do to avoid host immune responses?
They can mutate or recombine
How does HIV evolve by mutation?
- HIV inserts its DNA into our cells when reverse transcriptase converts RNA to DNA
- The viral DNA in our nucleus can then be transcribed into viral proteins
Does HIV have a high mutation and antigenic drift rate?
Yes
How does the flu evolve?
by recombination
What is recombination?
Flu recombination refers to a process called genetic reassortment that occurs when two different strains of the influenza virus infect the same host cell and exchange genetic material. This can lead to the creation of a new hybrid virus with characteristics from both parent strains.
When was the spanish flue first introduced?
In 1918
What caused the 1918 spanish flu?
a bird crossing the species barrier and transferring H1N1 bird flu
Which influenza infects humans?
Influenza type A
What triggered the 1957 Asian ‘flu epidemic?
Recombination events
What is antigenic shift?
When pathogens alter their antigens, making it harder for the immune system to deal with them
What pathogen undergoes antigenic shift?
Plasmodium falciparum
Why do we have to rely on our innate immune system for the first few days after being infected with a pathogen?
Because the primary response and the secondary response are slow
What does the immune system find it difficult to distinguish between?
Self, non-self, and altered self
What do ‘altererd self’ include?
malignant cells, apoptotic cells, oxidised proteins
What are the typical features of non-self?
Bacterial cell wall structures
Protein and peptide
structures/sequences from pathogens
Yeast carbohydrates Pathogen DNA Viral antigens on host cells
What does the blood brain barrier do?
It separates circulating blood from the brain extracellular fluid.
