B & T cells

Question 1

Where do T cells come from and where do they mature?

Answer 1

From haemapoeitc stem cell in bone marrow

& mature in thymus

Question 2

Where do B cells come from and where do they mature?

Answer 2

From haematopoietic stem cell in bone marrow

& mature in bone marrow

Question 3

Where are dendritic cells located in the body?

Answer 3

• Lymph node = follicular dendritic cells (B cell specific presenters)
• spleen = dendritic cells (T cell presenter)

Question 4

the difference b/w follicular dendritic cells (DC) & DC

Answer 4

FDC: derived from embryonic tissue
DC: derived from BM haematopoietic stem cell

Question 5

Which type of dendritic cell is a specific B cell presenter? Which type of APC presents to T cells?

Answer 5

• B cell presenter: follicular dendritic cells

- T cell presenter: dendritic cells in spleen

Question 6

What type of antigens do B cells interact with? What type of antigens do T cells interact with? Do both react to native antigen?

Answer 6

a) B cells intetract w/ T cells
b) T cells interact w/ processed Ag
c) No, only B cells react to native Ag

Question 7

What is the biological role of the CD4 and CD8 antigens on T cells?

Answer 7

• CD4: present on Th cells & holds the synapse tog. (on MHC II w/ Ag)
• CD8: present on Tcytotox. cells & holds the synapse tog. (on MHC I w/ Ag)

Question 8

Which class of MHC receptor do CD4+ and CD8+ T cells bind to? Which cells express class I and II?

Answer 8

• CD4+ binds to MHC II (on WBC)

- CD8+ binds to MHC I (on nucleated cells except neurons)

Question 9

List the three types of T helper cell (other than CD4+ T reg cells) that can be produced following antigen presentation by an APC to a naïve Thelper cell?

Answer 9

• Th1
• Th2
• Th17

Question 10

List the key effector function of Th1 cells with respect to humoral immunity?

Answer 10

secrete IFNgamma (cytokine) to:
> enhance macrophage activity
> stimulate B cells to produce IgG1 & igG3
> Activate cytotoxic T cells

Question 11

List the key effector function of Th2 cells with respect to humoral immunity?

Answer 11

secrete IL 4 (cytokine) to:
> enhance macrophage activity
> inc. intestinal mucus & peristalsis
> isotope switching of B cells => igG4, IgE, IgA

Question 12

Do B cells present antigen to Th1/Th2 cells or do these T helper lymphocytes present antigen to the B cells?

Answer 12

Th1/Th2 cells present Ag to B cells

Question 13

What is the main function of activated CD8+ lymphocytes (irrespective of T helper involvement in their activation)?

Answer 13

kill viable bacteria in cytosol of phagocytes & infected cells = kill cell to kill pathogen bc can’t be broken down in phagocyte

Question 14

What is T dependent humoral immunity? Explain what the benefit of this process is over T independent stimulation of B cells by antigen?

Answer 14

a) presentation of proetin/peptide Ag by B cells to primed T cells (Th1, Th2) in spleen/lymphoid tiss.
b) Benefit: can make long-lived Ab (IgA, IgG, IgE) compared to short-lived Ab (IgM)

Question 15

What process/cellular interactions are required to produce long lived plasma cells and memory B cells?

Answer 15

adaptive IR: B cell interact w/ Ag via BCR IgM, IgD => activated to form plasma cells & memory B cells

Question 16

Outline the steps/processes involved in the adaptive immune response to an extracellular infection?

Answer 16

1. APC present peptide Ag via MHC II to CD4+ naive Th cell (~ 8hrs)
2. Th cell => Th1, Th2, Th17 (2-3days)
3. Th1 release IFNgamma => enhance macrophage activity; B cell produce IgG1 & IgG3; activate Tcytotox. cells
4. Th2 release IL-4 => enhanced tiss repair; inc peristalsis; make IgG4 & IgE
5. Th2 release IL-5 => B cell proliferate & make IgA
6. Th17 release IL-17 => recruit neutro. & mono.

Question 17

Role of Th1, Th2 & Th17 summarised (cytokines; role; defence against)

Answer 17

. slide 29