Lecture 7

Question 1

What are the 5 types of t helper cells

Answer 1

Tfh, TH1, TH2, TH17, treg cells

Question 2

What do treg cells do

Answer 2

dampen inflammatory responses and secrete cytokine IL-10

Question 3

What does Th17 do

Answer 3

stimulate inflammation by secreting interleukin 17- helps trigger recruitment of neutrophils and macrophages

Question 4

What does Th2 do

Answer 4

recruit eosinophils to combat parasitic infections and inhibit Th1 proliferation

Question 5

What does Th1 do

Answer 5

assist in activation of cytotoxic t cells

Question 6

What does Tfh do

Answer 6

drives B cell differentiation into antibody secreting plasma cells. They secrete different combinations of cytokines that trigger antibody isotype class switching

Question 7

What do t helper cells do and their receptor

Answer 7

Augment/ help immune responses. Have CD4+ve

Question 8

What do T cytotoxic cells do

Answer 8

They specifically kill infected host cells. CD8+VE

Question 9

General structure of a t cell receptor

Answer 9

Made of two chains, an alpha chain and a beta chain. Structure is very similar to the FAB arm of an antibody.

Within each variable region, there are 3 hypervariable loops or complementary determining regions

Question 10

What does expression of t cell receptors on the cell surface require

Answer 10

Requires the association with additional proteins (Cluster differentation/ CD3)

Question 11

What do CD3 subunits contain

Answer 11

ITAMs in their cytoplasmic regions. When the whole complex bind to antigen, these motifs can be phosphorylated and we get down stream signalling.

Question 12

What are T cell receptor genes like

Answer 12

They’re very similar to antibody genes. There are two gene loci

Question 13

What’s the main difference between t cell receptor rearrangement compared to antibody rearrangement

Answer 13

Occurs in the thymus rather than the bone marrow

Question 14

Stages of t cell receptor diversity

Answer 14

1. Multiple copies of V region gene segments
2. a x b chain combination (junctional diversity)

CDR1 and CDR2 are encoded in the germline by the V segments. CDR3 corresponds to the V chain or the VDJ join so its very diverse

Question 15

What is B cell immunity important for

Answer 15

In defence against extracellular pathogens. They recognise free, “native” antigens that haven’t been processed

Question 16

What is T cell immunity for

Answer 16

Important in extracellular bacteria but also important in defence against intracellular pathogens.

Question 17

What do T cells require

Answer 17

Antigen presentation by cells expressing Major histocompatibility proteins

Question 18

What does histocompatibility mean

Answer 18

Determines whether a given antigen is recognised as coming from the host or from another source

Question 19

What are the two classes of MHC proteins

Answer 19

Class 1: expressed by all nucleated cells - non professional APCS. These present peptides derived from endogenous proteins to cytotoxic t cells.

Class 2: They’re expressed by certain leukocytes- professional APCs. They present peptides derived from exogenous proteins to helper t cells.

Question 20

Structure of MHC1 proteins

Answer 20

They’re made up of an alpha chain and a beta chain - they stabilize the molecule on the membrane. These genes are polymorphic. They are heterodimer made of an alpha chain and a b2-microglobulin.

Question 21

What’s the structure of MHC2 proteins

Answer 21

They’re made of two chains, the ones closest to the membrane are immunoglobulin like, the domains furthest away are the most polymorphic and bind to peptide. Alpha and beta subunits both contribute to the antigen binding cleft.

Question 22

Whats the structure of the peptide binding groove

Answer 22

The bottom is made of beta pleated sheets and the alpha helical region comes up out of the surface to form the sides of the domain

Question 23

Where do anchor residues bind

Answer 23

They bind to specificity pockets formed by polymorphic residues

Question 24

What’s a proteosome

Answer 24

A multi-subunit complex that breaks down misfolded proteins. They’re present in all cells

Question 25

Stages of antigen presentation of MHC1

Answer 25

1. Antigen processing to peptides in the proteosome
2. Peptide transport into endoplasmic reticulum (ER)
3. Peptide binding by MHC class 1
4. MHC class 1 presents peptide at cell surface

Question 26

Why is cross presentation important

Answer 26

Allows antigen presentation to cytotoxic t cells without the dendritic cells themselves being infected
Important in cytotoxic t cell responses in many tumours

Question 27

H