Lymphoid tissues

Question 1

Why is the lymphoid system vital?

Answer 1

Despite the abundance of T cells and B cells due to their specific TCR or BCR receptors it is unlikely the cells could detect threats around the whole body.

Question 2

Where does lymphopoieses occur?

Answer 2

Primary lymphoid organs are where lymphocytes are produced.

Question 3

Name some primary lymphoid organs?

Answer 3

Bone marrow
Thymus
Foetal Liver

Question 4

What are the hallmarks of the adaptive immune system?

Answer 4

Specificity – provided by a vast range of unique T cell and B cell receptors

Memory – rapid expansion in response to secondary encounter

Question 5

What is the primary site of haematopoiesis?

Answer 5

Bone marrow

White cell production increases during infection

* in foetus : All bones
\+ liver/spleen
in adults : Mostly flat bones,Vertebrae
Iliac bones
Ribs, Ends of long 
limb bones

Question 6

The B cell “repertoire” is generated in the bone marrow

Where does final maturation happen?

Answer 6

Final maturation occurs in the periphery

Question 7

Where do thymocytes go?

Answer 7

Immature T cells migrate from the bone marrow to the thymus (Thymocytes)

Question 8

What is the positive and negative selection for select for T cells?

Answer 8

Positive selection – can the T cell receptor signal

Negative selection – does it react against our own body

Question 9

What is thymus involution?

Answer 9

the shrinking of the thymus with age. Associated with a change in structure and a reduced mass.

Question 10

Name some secondary lymphoid organs?

Answer 10

Spleen
Lymph nodes
Appendix
Mucosal associated
Lymphoid tissue

Question 11

How do the arterial and venous connections in the spleen aid the lymphocytes?

Answer 11

Filter blood antigens quickly ( carry pathogens ) past distinct T and B cell zones in the spleen

Question 12

What are Peyer’s Patches?

Answer 12

Specialized secondary lymphoid tissues within the gut - Found below the epithelium of the ileum of the small intestine.

Lots of active B cells - allowing for mutation and selection of B cell antibodies

• get alot of microbial antigens in the gut so alot of B cells

Question 13

Follicles surround the Peyer’s Patches and connect to afferent lympathics. What does it contain?

Answer 13

highly enriched with B cells, and contains a high frequency of germinal centres.

Question 14

What are Germinal centres?

Answer 14

Germinal centre: anatomically restricted site where B cells undergo mutation and selection to generate high affinity antibodies

Question 15

What encircles the oral and nasal cavity to form the Waldeyer ring?

Answer 15

Pharyngeal, tubular, palantine and lingual tonsils encircle the oral and nasal cavity – form the Waldeyer ring

• Pathogens pass by this very often, they contain germinal centres and lymphoid follicles

Question 16

We have secondary lymphatic organs distributed around our bodies where T and B cells can become activated. How do they and the antigens get there?

Answer 16

Fluid drained from between tissue cells absorbed into lymph.

2 to 3 litres of lymph are returned to the blood each day (via superior vena cava).

Question 17

Each naive T cell recirculated once every x hours?

Answer 17

24

Question 18

Describe the Extravasation of naive T cells into lymph nodes?

Answer 18

Selectin binding allows the rolling Naive T cell to attach to the endothelial wall

Integrin binding occurs with ICAM-1 and LFA-1 causing transendothelial migration

Goes into the lymph node

Question 19

How are the antigens presented for the lymphocytes to see?

Answer 19

Antigen presentation. The display of peptides in the major histocompatibility complex I or II proteins such that the T cell receptor can attempt to bind them.

• dendritic cells, APCs etc