Week 4- Lymphoid Tissues

Question 1

What are the primary lymphoid tissues?

Answer 1

Bone marrow, thymus and fœtal liver

Question 2

What are the 2 hallmarks of primary lymphoid tissues?

Answer 2

1. Specificity- wide range of specific B and T cells

2. Memory- rapid response on second exposure

Question 3

Describe the characteristics of the bone marrow

Answer 3

Main site of haematopoeisis but not in a foetus (location is red bone marrow), replaced by fat as we get older (yellow bone marrow)

Question 4

Describe the route by which NK cells arise

Answer 4

Haemopoeitic stem cell goes to lymphoid progenitor goes to NK cell

Question 5

Describe the route by which B cells arise

Answer 5

Haemopoeitic stem cell goes to lymphoid progenitor goes to B cell progenitor which go to the spleen to mature

Question 6

Describe the route by which T cells arise

Answer 6

Haemopoeitic stem cells goes to lymphoid progenitor goes to T cell which can develop into one of 2 types: helper or cytotoxic

Question 7

What is an individuals repertoire?

Answer 7

The collection of B and T cells that they have

Question 8

What is the thymus?

Answer 8

Where immature T cells go to mature

Question 9

How is selection of T cells in the thymus carried out?

Answer 9

At first T cells are double negative (not CD4 or CD8)

1. Positive selection: is the receptor functional
2. Negative selection: is the cell self or non self (if it’s self it should be made to undergo apoptosis)
3. Final selection or exit (now its CD4 or CD8)

Question 10

What happens to the thymus as we age? What is the technical term for this

Answer 10

It gets smaller, as does the no of T cells we have. Known as thymic involution

Question 11

What is the main role of secondary lymphoid tissues?

Answer 11

To find the specific T cell against a pathogen

Question 12

What are the main secondary lymphoid tissues?

Answer 12

Spleen, lymph nodes, appendix, mucosal tissues

Question 13

Where can secondary lymphoid tissues be found and what systems are they connected to?

Answer 13

They are found all over the body and connected to blood the lymphatic system and blood so they can scan all antigens

Question 14

Describe the general structure of lymph nodes

Answer 14

They have distinct B and T cell zones with afferent and efferent vessels. They have connections to lymphatic vessels and arterial and venous connections.

Question 15

What do lymph node T cell zones contain and what is the function?

Answer 15

They contain fibroreticular networks that retain T cells and make chemokines to allow T cells to migrate

Question 16

What do lymph node B cell zones contain and what is the function?

Answer 16

Follicular dendritic cells that make chemokines to attract B cells and capture immune complexes

Question 17

Describe the general features of the spleen

Answer 17

Has afferent and efferent vessels, red and white pulp, very heavy connection to blood as it scans the blood thoroughly, also makes RBCs

Question 18

What are Peyer’s patches? Describe where they are found and their role

Answer 18

They are found underneath the epithelium of the ileum in the small intestine, they contain germinal centers where B cells undergo selection and mutation to form antibodies with high affinity

Question 19

Where are germinal centers found in the body?

Answer 19

Peyers patches and tonsils

Question 20

How are T cells extravased into lymph nodes?

Answer 20

They bind to selectin, activation of CD34 allows them to roll along the epithelium, then LFA-4 binding means they can migrate into the lymph node