Lymphoid tissues

Question 1

Function of primary lymphoid tissues

Answer 1

Lymphopoieses - production of lymphocytes

Question 2

3 examples of primary lymphoid organs

Answer 2

1. Thymus
2. Bone marrow
3. Foetal liver

Question 3

Where is the B cell repertoire generated?

Answer 3

Bone marrow

Question 4

Where do immature T cells mature?

Answer 4

Thymus

Question 5

What is the difference between positive and negative selection?

Answer 5

Positive selection - if the T cell receptor can signal properly it is given signals to survive

Negative selection - if T cells are self reactive they are given signals to undergo apoptosis.

Question 6

What is thymic involution?

Answer 6

The shrinking of thymus with age causing much reduced output of new T cells.

Question 7

What is the function of secondary lymphoid tissues?

Answer 7

Secondary lymphoid organs are where lymphocytes can interact with antigens and other lymphocytes.

Question 8

Give 5 examples of secondary lymphoid organs

Answer 8

1. Spleen
2. Lymph nodes
3. Appendix
4. Mucosal associated
5. Lymphoid tissue

Question 9

Where is lymphoid tissue located?

Answer 9

Located all around the body e,g, lymph nodes and distinct regions within tissue e,g, spleen.

Question 10

How are lymphoid tissues interconnected?

Answer 10

By blood and lymphatic system

Question 11

What is the structure of lymph nodes and spleen?

Answer 11

Distinct T and B cell zones.

Afferent and efferent lymph

Arterial and venous connection

Question 12

What are peyer’s patches and where are they found?

Answer 12

They are specialised secondary lymphoid tissue found below the epithelium of the ileum. They contain follicles highly enriched with B cells and a high frequency of germinal centres.

Question 13

What are germinal centres?

Answer 13

Anatomically restricted sites where B cells undergo mutation and selection to generate high affinity antibodies.

Question 14

What is the Waldeyer ring?

Answer 14

4 tonsils - pharyngeal, tubular, palantine and lingual tonsils encircling the oral and nasal cavity

Question 15

How often does a naive T cell recirculate?

Answer 15

Once every 24 hours

Question 16

How does extravasation of naive T cells into lymph nodes occur?

Answer 16

First rolling adhesion by binding to selectin, This is followed by firm activation by chemokines then firm adhesion by binding to integrin. Finally the T cell escapes the vascular wall by diapedeses.

Question 17

How are antigens transported to lymph nodes?

Answer 17

Carried by professional antigen presenting cells such as dendritic cells. These move from the skin for example into afferent lymph into lymph nodes. They can also enter the venule to enter circulation.