Lec 4 - Adaptive - Cell Mediated

Question 1

What are thymus independent and thymus dependent antigens?

Answer 1

TI - antigens can stimulate a B cell response w/out the aid of T cells

TD - antigens require T cells to stimulate a B cell response

Question 2

What B cell activities are aided by T cells?

Answer 2

B cell somatic hypermutation and class switching

Question 3

Describe the 3 main functions of CD4+ve T helper cells

Answer 3

• helps B cell make antibodies
• aid in making cytotoxic T cells
• release of cytokines to stimulate macrophages, NK cells (leukocytes)

Question 4

What is the main function of CD8+ve cytotoxic T cell?

Answer 4

kill virally infected host cells

Question 5

Draw a Tcell receptor that recognises antigens. describe what it looks like and the exons that encode it

Answer 5

• looks like Fab arm of an Ab
• separate exons encode V & C regions, only 1 exon needed for C region whereas multiple exons for V region

Question 6

How do T cells recognise an antigen (generally) and how does this differ to B cells?

Answer 6

B cells can recognise soluble, free antigens whereas T cells recognise antigens that are present of Major Histocompatibility proteins that have been processed

Question 7

Describe what cells present and what cells recognise MHC I / II proteins

Answer 7

PRESENT

• MHC I - all nucleated cells
• MHC II - macropages , dendrites, B cells

RECOGNISE…

• MHC I - CD8+ve cytotoxic
• MHC II - CD4+ve T helper

Question 8

1. Draw a complex between a Cytotoxic T cell and a virally infected host cell
2. State how the protein gets to be on MHC I on surface

Answer 8

2. in the cytosol the pathogen components degraded (proteasome) and directed to ER where they interact w/ MHC I and are shuttled to surface and expressed

Question 9

1. Draw a complex between CD4 and macrophage
2. State how the antigen gets to be on the surface w/ MHC II

Answer 9

2. macrophage (eg) takes up the pathogenic material, endosome formation and protein interacts w/ MHC II in endosome, fuses to the surface

Question 10

T CELL EFFECTOR FUNCTION

Question 11

What are cytokines? Describe them and list 4 examples

Answer 11

cytokines are hormones of immune system, produced and act locally on cells with cytokine receptors (eg NK cells, macrophages)

• interleukins
• TNF
• interferons (virally infected host cells)
• chemokines (chemotaxis)

Question 12

Draw a diagram that illustrates the function of TH1 cells

Answer 12

Question 13

What are the 2 effects of TH1 cells and give an alternative name

Answer 13

INFLAMMATORY CD4 cells

• PRODUCTION of IL-2, TNFa, IFNy. cytokine release, activation of macrophages, promotes inflammation
• enables B cells to produce opsonising antibody IgG

Question 14

What is the function of TH2 cells and how does it do this?

Answer 14

• allow response to helminths/allergens
• TH2 cell binding to B cells allows class switching to IgE antibody
• production of IL-4,6,10

Question 15

Give an alternative name for TH2 cells

Answer 15

HELPER CD4 cells

Question 16

What are TREGs?

Answer 16

• T regulatroy cd4 cells
• produce anti-inflammatory cytokines (eg IL-10)
• reduces inflammation by B cells
• overall leads to the suppression of the immune system after infection dealt w/

Question 17

Describe the mode of action of CD8+ve cytotoxic T cells

Answer 17

• Bind to virally infected host cells via MHC I
• secrete perforin to allow protease to be secreted in and cause caspase cascade to induce apoptosis
• can also secrete IFN/TNF for recruitment of macrophages

Question 18

How do CD8 cells differ from NK cells?

Answer 18

CD8 cells can kill 100s infected cells and can only recognise specfici cells presenting MHCI