Lymphoid organs & cellular traffic

Question 1

What are the 2 types of lymphoid tissue.

Answer 1

Primary (central) and secondary (peripheral)

Question 2

What is primary lymphoid tissue?

Answer 2

Tissue where lymphocytes develop (produced, mature, secreted) e.g. bone marrow and thymus

Question 3

What is secondary lymphoid tissue?

Answer 3

Tissue where lymphocytes are maintained and adaptive immune responses are initiated e.g. lymph nodes, spleen and MALT (mucosa-associated lymphoid tissue)

Question 4

What are some examples of MALT

Answer 4

Tonsils, BALT, appendix, Peyer’s patches

Question 5

Where are B and T cells produced and where do they mature?

Answer 5

Produced in bone marrow but T cells mature in thymus.

Question 6

What are immune cell precursors

Answer 6

Haematopoietic SCs

Question 7

What is a lymph node?

Answer 7

Bi-lobed organ lying over the heart and major blood vessels

Question 8

What are the lobules separate by and what do they consist of?

Answer 8

Connective tissue trabeculae and contain cortex and medulla

Question 9

What is a thymocyte?

Answer 9

Immature T cell which migrates from bone marrow to thymus

Question 10

What is the site of positive selection

Answer 10

The cortex - tightly packed with cells containing immature, proliferating thymocytes

Question 11

What is the site of negative selection

Answer 11

The medulla - loosely packed with cells containing more mature thymocytes

Question 12

What are the 3 thymic epithelial cells involved in T cell development?

Answer 12

Epithelial nurse, cortical, medulllary

Question 13

What is the site of lymphocyte activation by antigen?

Answer 13

Peripheral lymph organs

Question 14

How do lymphocytes and lymph reutrn to the blood

Answer 14

Thoracic duct

Question 15

How do antigens from sites of infection reach lymph nodes

Answer 15

Lymphatics

Question 16

What does CD stand for?

Answer 16

Cluster of differentiation

Question 17

What do T cells express?

Answer 17

Th - CD4 (class II) and Tc- CD8 (classI)

Question 18

When do T cells lose expression of CD4 or CD8?

Answer 18

When they differentiate

Question 19

What defines B cells?

Answer 19

CD19+

Question 20

What do lymph nodes do?

Answer 20

Filter and trap antigen from lymph

Question 21

What do the nodes consist of?

Answer 21

Cortex (B cell area), paracortex (T cell area) and medulla

Question 22

How do T cells enter a lymph node?

Answer 22

Across high endothelial venules in cortex

Question 23

What do T cells do?

Answer 23

Monitor antigen presented by macrophages and dendritic cells

Question 24

What do T cells do if they don’t encounter an antigen?

Answer 24

Leave node in efferent lymph

Question 25

What do T cells do if they encounter an antigen?

Answer 25

Proliferate and differentiate into effector cells

Question 26

What do T cells have on their surface?

Answer 26

L-selectin, LFA-1 and chemokine recepotor

Question 27

What binds to L-selectin

Answer 27

GlyCAM-1 and CD34 - causes rolling interaction

Question 28

What is LFA-1 activated by?

Answer 28

Chemokines bound to ECM.

Question 29

What does LFA-1 bind to?

Answer 29

ICAM-1

Question 30

What is diapedesis?

Answer 30

When the lymphocyte leaves the blood and enter the lymph node

Question 31

Where do antigens enter the lymph node from?

Answer 31

The afferent lymphatic

Question 32

What is the germinal centre?

Answer 32

Transient structure of intense proliferation (B cells start proliferating when antigen enters)

Question 33

What are lymphoid follices?

Answer 33

Initially loose network of follicular dendritic cells (FDCs) in region rich in B cells

Question 34

How are FDCs different from conventional DCs?

Answer 34

Display antigen to B cells (cross link Ag with B cell receptors and form Germinal Centres)

Question 35

What do lymphocytes recirculate between?

Answer 35

Bloodstream, lymph nodes and lymphatics

Question 36

What is the largest secondary lymphoid organ

Answer 36

The spleen

Question 37

BALT

Answer 37

Bronchus-associated lymphoid tissue

Question 38

GALT

Answer 38

Gut-associated lymphoid tissue

Question 39

Where are Peyer's patches found?

Answer 39

In the intestinal lining

Question 40

What is an M cell?

Answer 40

Specialised epithelial microfold cells that transport antigens into the lymphoid tissue

Question 41

Where are intestinal lymphocytes found?

Answer 41

In organised tissues (peyer's patches) where immune responses are induced OR scattered throughout intestine (epithelium and lamina)

Question 42

HEV

Answer 42

High endothelial venule