L8-9-10 immunity against infection

Question 1

When viruses infect cells, what type of innate response occurs early in infection?

Answer 1

Type 1 interferons are produced. IFN-alpha and IFN-beta. These interferons bind to an uninfected cell and induces synthesis of anti viral molecules.

Question 1

In viral infections, Type 1 interferons induce synthesis of antiviral molecules. What else do they induce synthesis of?

Answer 1

1. 2’-5’ oligoadenylate synthetase is made, which then synthesises adenine trinucleotide, which activates endonucleases, which degrades viral mRNA.
2. Protein kinase which phosphorylates and inactive eIF-2 which inhibits protein synthesis.

Question 2

In viral infections, the early response to infection is using type 1 interferons. Type 2 interferons are then activated. Which interferon is type 2 and what does it activate?

Answer 2

IFN gamma.

This is secreted by T cells and NK cells. It inhibits TH2 response (antibodies not needed to kill viruses). Promotes TH1 response and recruits macrophages.

Question 3

Interferons are used to target virus infections. What is the therapeutic interferon?

Answer 3

recombinant IFN-alpha

Question 4

What are the two innate defences against viruses?

Answer 4

Interferons and NK cells

Question 5

How do NK cells kill?

Answer 5

They are granular cells which release granules of perforin and granzyme.

Question 6

How do NK cells distinguish between virally infected and uninfected cells?

Answer 6

They have activating and inhibitory receptors.

Activating receptors will recognise carbohydrate ligands and will trigger killing. When cells are infected, viruses cause MHC expression to be reduced. So virally infected cells tend not to have MHC molecules. Without MHC, the inhibitory receptors which normally recognise MHC molecules can’t inhibit NK cells as there are no MHC molecules to recognise!

Question 7

Which components of the acquired immunity target viruses?

Answer 7

1.Cytotoxic T cells - recognise MHC class 1
2. Cytokines eg IFN gamma which activate macrophages
3. Antibodies

Question 8

Cytotoxic T cells kill virally infected cells by inducing apoptosis or by releasing cytokines. What are the two mechanisms of CTLs that induce apoptosis?

Answer 8

1. Secretion of cytotoxic granules (perforin and granzyme)
2. Binding of Fas ligand on CTL to Fas on target cell.

Question 9

What cytokine do CTLs release in response to virally infected cells, and what does this cytokine do?

Answer 9

IFN gamma - type 2 interferon.

Inhibits viral rep
Upregulated MHC 1 and 2 expression
Increases macrophages
Promotes NK killing

Question 10

how do antibodies protect against flu?

Answer 10

Antibodies recognise antigens on surface of flu virus - haemagluatnin and neuraminidase.

Question 11

What is involved in the response to influenza?

Answer 11

Both antibodies and CTL response. This is different to HIV, which only involves CTLs. Antibodies do not seem to protect against HIV.

Question 12

What type of virus is Covid 19?

Answer 12

ss postive RNA virus

Question 13

Leishmania is a parasite that survives inside macrophages and therefore is hidden from antibodies. Which type of response, either TH1 or TH2 would cause the infected organism to die?

Answer 13

TH2 as this is an antibody response, and antibodies cannot fight leishmania.