CSIM 1.13 - Introduction to Immunology 2

Question 1

What anatomical sites may be defined as central lymphoid tissue?

Answer 1

Bone marrow

Thymus

Question 2

Where to T-cells mature?

Answer 2

Thymus

Question 3

What anatomical sites may be defined as peripheral lymphoid tissue?

Answer 3

Lymph nodes
Spleen
Mucosa associated lymphoid tissue (Payer’s patch)

Question 4

Where is the thymus located?

Answer 4

In the thorax (anterior mediastinum)

Question 5

Describe the physical changes observed in the thymus during life?

Answer 5

Enlarges during childhood (active)

Post-puberty it in-volutes (reduction in functioning mass)

Question 6

How is the thymus defined histologically?

Answer 6

Distinctive outer cortex

Inner medulla

Question 7

What is Di-George’s syndrome?

Answer 7

Hereditary condition resulting in an inability to fight infections (immunodeficiency) in association with absence of parathyroid/thymus.

Question 8

Where do T-cell progenitors first start maturing within the thymus?

Answer 8

Cortex - (Sub-capsular region)

Question 9

The Interactions between which cells play an important part in the development of maturing T-cells?

Answer 9

T-cell receptor and MHC peptide complexes displayed by the thymus corticle epithelial cells

Question 10

The initial developing T-cell displays which receptors?

Answer 10

CD4
CD8
T-cell receptor

Question 11

How are CD8 receptor expressing T-cells created?

Answer 11

T-cells with receptors able to recognise MHC-class 1 receptor are given survival and maturation signals
Eventually they stop expressing CD4 receptors and only maintain CD8

Question 12

How are CD4 receptor expressing T-cells created?

Answer 12

T-cells with receptors able to recognise MHC-class 2 receptor are given survival and maturation signals
Eventually they stop expressing CD8 receptors and only maintain CD4

Question 13

Describe central tolerance (negative selection)?

Answer 13

Thymocytes which recognise MHC-1//MHC-2 too avidly are given signals which drives them to apoptosis
Thymocytes responding to self-peptide antigens are also eliminated in the process

Question 14

Where do lymphocytes begin to interact?

Answer 14

Lymph nodes: dendritic cells, T-cells, B-cells

Antigen presentation and Antigen recognition

Question 15

Where are lymph nodes not present?

Answer 15

CNS

Question 16

Within lymph nodes where do macrophages and plasma cells collect?

Answer 16

Medullary cords

Question 17

Within lymph nodes which specific area is T-cell dense?

Answer 17

Para-corticle area

Question 18

Within lymph nodes which specific area is B-cell dense?

Answer 18

Primary lymphoid follicle (once activated B-cell proliferation and maturation occurs here - Affinity maturation)

Question 19

What is required for dendritic cell activation from senescent form?

Answer 19

Inflammation

Question 20

Describe the clonal theory of selection?

Answer 20

One lymphocyte may have many copies of a receptor although this receptor is specific to one particular antigen only (lock and key)

Question 21

What is the fate of B-cells once activated by specific T-cells with the same antigen recognition?

Answer 21

Some become IgM secreting plasma cells
Some migrate to the B-cell rich areas of the lymph node (germinal centres) and intense proliferation occurs forming progeny with high affinity for antigen (affinity maturation)

Question 22

What are the products of germinal centres?

Answer 22

IgE
IgA
IgG
Memory B-cells

Question 23

Name the four classes of pathogens that the immune system protects against and give examples of conditions caused by each?

Answer 23

1. Extracellular bacteria/parasites/fungi - Pneumonia + Tetanus
2. Intracellular bacteria/parasites - Leprosy + Leishmansiasis + Malaria
3. Viruses (Intracellular) - Small pox + Flu + Chicken pox
4. Parasitic worms (Extracellular) - Ascariasis + Schistosomiasis