Lymphoid Tissues (11)

Question 1

What are the primary lymphoid tissues?

Answer 1

• thymus
• bone marrow
• foetal liver

Question 2

What happens in primary lymphoid organs?

Answer 2

Lymphopoiesis- producing lymphocytes: T, B and NK cells

Question 3

Where is the B cell “repertoire” generated?

Answer 3

Bone marrow

Question 4

Where is final maturation of B cells?

Answer 4

in peripheral tissues e.g. spleen

Question 5

Where do immature T cells migrate to from the bone marrow (in order to develop)?

Answer 5

Thymus

Question 6

What are the hallmarks of the adaptive immune response?

Answer 6

• specificity: provided by a vast range of unique T and B cell receptors
• memory: rapid expansion in response to secondary encounter

Question 7

What is a T/B cell ‘repertoire’?

Answer 7

the range of genetically distinct BCRs or TCRs present in a host–> larger repertoire means more threats can be recognised

Question 8

What is positive selection of T cells?

Answer 8

deleting cells whose TCR cannot recognise and receive signals

Question 9

What are double negative T cells?

Answer 9

do not express CD4, CD8, or natural killer (NK) cell markers

Question 10

What are double positive T cells?

Answer 10

express both CD4 and CD8

Question 11

What is negative selection of T cells?

Answer 11

deleting cells that recognise self-antigens/ react against our own body by apoptosis

Question 12

What is thymic involution?

Answer 12

shrinking of thymus with age–> change in structure and reduced mass, more fatty

Question 13

What are the secondary lymphoid tissues?

Answer 13

• where lymphocytes interact w/ antigens and other lymphocytes
• interconnected via lymphatic system and blood
• spleen
• lymph nodes
• appendix
• mucosal associated lymphoid tissue

Question 14

What are fibroreticular cells?

Answer 14

• type of fibroblast
• recruit and retain T cells
• produce chemokines e.g. CCL19, CCL21–> cause naive T cells to migrate
• produce IL-7 cytokine to promote T-cell survival

Question 15

What are follicular dendritic cells?

Answer 15

• stromal cells in B cell zone of lymph nodes
• produce chemokine CXCL13, which cause B cells to migrate
• BAFF cytokine= B cell survival factor

Question 16

What are the epithelial barriers?

Answer 16

• first line of defence against infection
• physical barrier
• connected to extensive lymphatic network e.g. Peyer’s patches

Question 17

What are Peyer’s patches?

Answer 17

• gut associated lymphoid tissue (specialised 2y lymphoid tissue)
• found below epithelium of ileum
• receive antigen either directly from lymphatic drainage from lumen or from M cells
• follicles highly enriched w/ B cells and germinal centres

Question 18

What is a germinal centre?

Answer 18

anatomically restricted site where B cells undergo affinity maturation and class switch recombination to generate v high affinity antibodies

Question 19

What migrates in the lymph to and from secondary lymphoid organs?

Answer 19

antigens and lymphocytes

Question 20

How do naive T cells undergo extravasation from the high endothelial venule into lymph node?

Answer 20

• L- selectin on naive lymphocyte engages CD34 on HEV–> selectin binding and rolling along
• LFA-1 integrin binds ICAM, allowing cell to migrate across endothelium into lymph nodes

Question 21

Which cells migrate out of site of inflammation in the lymph?

Answer 21

dendritic cells, so they can present antigens

–> head to T cell zone of 2y lymphoid tissue to interact w/ T cells–> screen for complementary receptor