Microbiology/Immunology

Question 1

What is positive and negative selection in terms of T cell development?

Answer 1

Positive selection ensures the T cell is capable of binding MHC
Negative selection kills the T cell if it binds too strongly

Question 2

What is the role of AIRE in central tolerance?

Answer 2

It is a TF which causes medullary epithelial cells in the thymus to present tissue specific antigens to developing T cells, contributing to negative selection if bind too strong.

Question 3

How does regulation induce tolerance?

Answer 3

Induced Tregs release immunosuppressive cytokines; IL-10 and TGF-B as well as up regulating CTLA4 which outcompetes CD28 and stops costimulation

Question 4

What gene mutations can cause loss of central and peripheral tolerance?

Answer 4

AIRE in central–> APECED

Foxp3 in peripheral (no tregs)–> IPEX

Question 5

What are two ways to activate autoimmunity?

Answer 5

Molecular mimicry

Infection; releases Ag and activates DC providing a signal 2

Question 6

What are the 3 main bacteria that cause meningitis in adults?
What about in neonates under 3 months?

Answer 6

Neisseria Meningitidis
Haemophilus influenze type B
Strep penumoniae

Strep group B
E.coli
Listeria monocytogenes

Question 7

What are some specific and non-specific clinical features of meningitis?

Answer 7

Non- specific

• Fever
• Headache
• Nausea/vomiting

Specific

• Stiff neck
• Photophobia
• Non-blanching rash`

Question 8

What are the relative protein and WBC in viral, bacterial and TB meningitis

Answer 8

WBC from small to large: viral, TB, bacterial

Protein; viral, bacterial, TB

Question 9

What do we treat meningitis with usually? Is it different in children?

Answer 9

Cefotaxime, add IV pen and gentomyoicin in kids

Question 10

What is the most common cause of encephalitis?
Whats the main clinical distinction?
What do we treat it with?

Answer 10

Usually viral; HSV main cause
Altered conscious state
Treat with acyclovir

Question 11

What is the difference between neurotropic, neuroinvasive and neurovirulent?

Answer 11

Neurotropic- capable of replicating in nerve cells
Neuroinvasive- capable of infecting CNS
Neurovirulent- capable of causing disease in the NS

Question 12

What is the main cause of viral meningitis?

Answer 12

Enteroviruses

Question 13

How can viruses enter CNS without being attacked?

Answer 13

Up peripheral nerve where no MHC class 1

Question 14

In terms of rabies:

• Is it high/low neuroinvasive and neurovirulent?
• Where does it replicate?
• Where does it go after that?

Answer 14

High for both
In the nerve cells- obligatory part of its life cycle
Goes into salivary glands, it also makes you more aggressive and want to bite

Question 15

In terms of herpes simplex virus

• Is it high/low neuroinvasive and neurovirulent?
• Where does it infect and then stay latent?
• How does it cause encephalitis?

Answer 15

Low neuroinvasive but high neurovirulent
Infects mucosal surfaces, will be latent in ganglia then reinfect
When it reactivates it can also travel the other way up into the CNS causing encephalitis

Question 16

In terms of varicella-zoster virus:

• How does it enter the nerves?
• Where does it go to be latent?
• What does it reactivate as?

Answer 16

Spreads via the blood, enters nerves from the resulting rash
Latent in dorsal root ganglia
Reactivation causes shingles along a dermatome

Question 17

In terms of poliovirus:

• Is it high/low neuroinvasive and neurovirulent?
• Is nerve a part of its obligatory life cycle
• How does it enter the CNS

Answer 17

• Low neuroinvasive but high neurovirulence
• No! gets in nerves by accident
• Comes through contaminated food, absorbed by gut and enters lymph where it causes viremia. Crosses BBB to live in anterior horn of spinal cord- how it causes paralysis