Feb. 7th (Exam 1) Flashcards
What are the general ways that pathogens try to evade the immune system?
- Genetic variation
- Mutation and recombination
- Gene conversion
- Hiding
- Sabotage and subversion
What do we call different strains of a pathogen?
Serotypes
How do we identify the serotypes?
Antibody based serological assays.
What is the blood serum?
This is just the clear liquid with all proteins and no cells.
In the mutation and recombination, how does this happen?
Normally we gain antibodies that provide us protective immunity against the glycoproteins of the viral envelope.
But when an epidemic happens, we can see long term survival of the pathogen due to new mutant strains that avoid the protective immunity.
What is the idea of antigenic drift?
When we see long term survival of the pathogen due to new mutant strains that avoid the protective immunity.
What is gene conversion?
When gene at the expression site is cleaved and replaced by another homologous
Describe an example of gene conversion as put in the notes.
African trypanosome that causes sleeping sickness has a surface formed by a glycoprotein.
There are over 1000 variable surface glycoproteins but only one is expressed at a time.
How does this work during the course of an infection?
There is an antibody response to the dominant trypanosome and we see clearance, causing selection of minority forms.
One eventually becomes dominant and it causes severe symptoms over time.
What is the human virome?
This is the sum of all the viruses that exist within the human host that provide more benefit than harm
What is latency?
What type of avoiding mechanism does this constitute?
Dormant state that doesn’t cause disease.
Hiding
Explain what happens in Epstein Barr Virus in reference to hiding.
It will infect B cells which will proliferate and produce the virus.
Then we see stimulation of EBV specific T cells.
The result is a large amount of mononuclear WBCs.
Most get cleared by the CD8 T-cells but some of the B cells still have it.
Reactivation can cause malignant transformation.
Explain how HHV-5 or CMV can sabotage and subverbe the immune system.
There are like 10 proteins that exist that can interfere with NK and CD8 T-cell activation.
How does sabotaging a macrophage work?
Tuberculosis - when it is phagocytized, it prevents the fusion of the phagosome with lysosome.
Listeria something will escape the phagosome and hang out in the cytosol.
What are some other examples of sabotage?
- The cause of syphilis coats itself with human proteins
- The capture of cellular genes that encode cytokines and their receptors
- Making proteins that interfere with the complement system or the MHC presentation.
What are superantigens?
These are toxins that are produced by bacteria that can activate many different T cell clones
This can activate up to 20% of the T cells.
We see a cross link between the antigen presenting cells MHC2 and the T-cell receptor of the CD4 type that leads to an ineffective T cell response.
What are staphylococcal super-antigen like proteins (SSLPs)?
This is similar to the superantigens, but instead the protein binds to an antibody on the pathogen, preventing the terminal complement protein C5 from starting the pathway.
