Lecture 14 – Adaptive immune system - focus on β cells

Question 1

Lymphoid progenitor cells (4)

Answer 1

20-30% peripheral WBCs.
6-10 um.
Stimulated by Ag –> effector –> memory.
B (BM) / T (Thymus).

Question 2

Role of thymus in T cell development (4)

Answer 2

T cells mature in the thymus.
Immature T-cells develop in BM, migrate to the thymus to encounter self-antigen.
During this journey many T cells die via apoptosis.
Thymus enlarges during childhood and then atrophies at puberty.

Question 3

T cell subsets (5)
5
4
4
3
3

Answer 3

On sheet

Question 4

TCR - T-cell receptor (3)

Answer 4

Dimeric molecule; ab/gd chains linked by S-S.
Variable chain has hypervariable regions which are antigen binding sites.
CD3 identifier of T-cell.

Question 5

MHC (Major Histocompatibility Complex) (5)

Answer 5

Found on surface and binds peptides from antigen and present to T cell.
MHCI - All NUCLEATED cells.
MHCII - APC

MHCI - CD8 , signal for cytoxic response.
MHCII found on APC presents peptide to CD4+ T-cells to get immune response- cytoxic/humoral.

Question 6

APCs (5)

Answer 6

Dendritic cells - Irregulary shaped
Macrophages
B-cells
Endothelial cells (certain conditions)
Tissue specific
LANGERHAN cells in skin

Question 7

3 signals to get correct T cell activation (3)

Answer 7

3 signals to get correct T cell activation
• Peptide bound in MHC (I or II) ligates cognate T cell receptor.
• Costimulation by ligation of CD80/86 to CD28.
• Modulation of signal by cytokine production.

Question 8

Thymus (-ve/ve selection) (2)

Answer 8

• T-cells in the thymus enter as thymocytes not expressing either CD4 or CD8 (double negative), go through a stage of expressing both (double positive) followed by a decision be either CD4+ or CD8+.
• Are positively selected to bind to molecules called MHC and negatively selected if bind self-peptides (‘education’).

Question 9

CD4 (5)

Answer 9

T helper/regulatory cells.
Activates cytoxic cells.
Humoral immune response.
Produce g interferon
Activates B cells to produce antibodies.

Question 10

CD8 (5)

Answer 10

Eliminates intracellular infections.
Role in anti-tumour immunity/rejection of transplants.
Releases cytolytic target molecules.
Releases toxins - perforin.
Apoptosis.

Question 11

NKT cells (4)

Answer 11

• Express T cell markers and NK cell markers.
• Large cell population.
• Respond to glycolipids such as a-galactosyl-ceramide.
• Restricted through CD1d.