Theme 1 - tissues

Question 1

what are primary lymphoid tissues

Answer 1

• involved in development and differentiation of lymphocytes
• Thymus (T cells)
• Bursa equivalent tissues (foetal liver and adult bone marrow) B cells

Question 2

what is the role of secondary lymphoid tissues

what do they include

Answer 2

• allow ANTIGEN ACCUMULATION
• allow ANTIGEN PRESENTATION to both naïve and memory lymphocytes
• include the MUCOSA, LYMPH NODES and SPLEEN

Question 3

what are the tertiary lymphoid tissues

Answer 3

• comprise all the remaining lymphoid tissues in the body (eg skin)
• contain only a few lymphocytes normally
• may be INVADED during inflammation by unique MEMORY LYMPHOCYTES

Question 4

what is the role of the thymus
what happens to it with age
structure
how do cells enter
where do they travel to in the thymus during maturation
what affects thymocyte development
what happens to those cells that don’t leave the thymus

Answer 4

• produces LYMPHOCYTES
• provided env for T cell MATURATION and EDUCATION
• SHRINKS with age
• 2 lobes divided into lobules by TRABECULAE
• each lobule has OUTER CORTEX & INNER MEDULLA
• cells enter as THYMOCYTES and surrounded by EPITHELIAL cells and others eg INTERDIGITATING DENDRTIC CELLS and MACROPHAGES
• cells move from CORTEX to MEDULLA while differentiating into T cells
• in cortex THYMIC NURSE cells affect thymocyte development
• if the T cell doesn’t leave, it undergoes APOPTOSIS

Question 5

what % of original thymocytes make it through the thymus into circulation as naïve T cells

Answer 5

5%

Question 6

when cells enter thymus as THYMOCYTES what do they express/not express
then what do they express in the next stage
and finally

Answer 6

do not express CD4 or CD8 
(double neg) 
- then express BOTH double positive 
- finally express one or the other 
- expression of CD3 and TCR  INC as they pass through thymus

Question 7

what is TCR

Answer 7

T cell receptor

Question 8

how are thymocytes educated in the thymus

how long is this process

Answer 8

POSITIVELY selected to bind to MHC molecules
NEGATIVELY selected if they bind to SELF peptides
- takes 1-3 weeks

Question 9

how do B cells develop

what -ve and +ve selection

Answer 9

immature B cells mature under local influence of GROWTH factors (from stromal cells)

• EDUCATED to not bind self molecules, if it does NEGATIVE SELECTION and it will undergo apoptosis
• EDUCATED to respond to SURVIVAL factors (POSITIVE SELECTION)
• then released as naïve B cells which are functionally immature

Question 10

what % of B cells do not undergo apoptosis and can leave the bone marrow

Answer 10

10%

Question 11

what is lymoh formed from

Answer 11

blood components from capillaries enter tissues making extracellular fluid that provides food and gas exchange
(tissue fluid)
- extracellular fluid drains into LYMPHATIC VESSELS

Question 12

what 2 things use lymphatics to migrate around the body

Answer 12

lymphocytes and leukocytes

Question 13

how are lymphocytes transported around the vessels

Answer 13

bind to ADHESION MOLECULES on the endothelial cells that line blood vessels
- up and down regulation of adhesion molecules allow movement of cells

Question 14

how is movement in the lymphatics aided

Answer 14

• smooth muscle cell movement
• arterial pressure due to close association with blood vessels
• valves prevent backflow

Question 15

how are leukocytes transported around the vessels

give an example of the what binds and what it binds to

Answer 15

• use HOMING RECEPTORS (adhesion molecules) to bind to ENDOTHELIUM lining of blood vessels
• LFA-1 binds to ICAM-1 on endothelial cells

Question 16

what is homing

Answer 16

traffic of cells through body to specific areas

Question 17

describe the lymph nodes 
structure
size
where do cells come from 
where do they go

Answer 17

• small bean shaped tissue aggregates at junctions of major lymphatic vessels
• 1-25mm diameter, larger if inf
• surrounded by CAPSULE, supported by RETICULUM
• 3 main areas: CORTEX, PARACORTICAL AREA and MEDULLA
• cells flow from cortex–>para–> medulla
• cells enter from HEV (HIGH ENDOTHELIAL VENULES) and return via thoracic duct
• cells drain into EFFERENT LYMPHATIC at the HILUS

Question 18

which part of the lymph node do T cells collect

Answer 18

paracortical areas

Question 19

which part of the lymph node do B cells collect

Answer 19

outer cortex

Question 20

what is found in paracortical area of the lymph node

Answer 20

contains ANTIGEN PRESENTING CELLS,

large LYMPHOCYTES and ACTIVATED cells

Question 21

what is found in the medulla of the lymph node

Answer 21

PLASMA cells secreting antibody

Question 22

what is a follicle in the lymph node

Answer 22

B cells forming dense aggregates

• PRIMARY follicles= dense and uniform
• SECONDARY follicles cont larger cells associated with MACROPHAGES forming GERMINAL centres w/ HIGH CELL PROLIFERATION

Question 23

what are the two parts of the spleen

Answer 23

red pulp and white pulp

Question 24

what is the function of the red pulp in the spleen

Answer 24

NON IMMUNOLOGICAL:

filters damages or ages cells

Question 25

what is the function of white pulp in the spleen

Answer 25

IMMUNOLOGICAL ROLE: | develop immune responses

Question 26

what is PALS

Answer 26

PERIARTERIOLAR LYMPHATIC SHEATH- cells and tissues surrounding major arterial branches

Question 27

the B dependent area of the spleen consists of what

Answer 27

lymphoid follicles

Question 28

the T dependent area of the spleen consists of what

Answer 28

PALS

Question 29

what is MALT

Answer 29

Mucosa-associated lymphoid tissue

Question 30

describe MALT

Answer 30

diffusely distributed lymphoid tissues in lining of GI, resp and urogenital tracts - gut-associated lymphoid tissue (GALT) and Bronchus ALT (BALT) are best characterisedBronchus ALT (BALT) a

Question 31

GALT is made up of what

Answer 31

Peyer's patches and isolated follicles in colonic submucosa - lymphocytes also found in lamina propria, intestinal epithelium & in lumen of intestine epithelium & in lumen of intestine

Question 32

describe Peyer's patches

Answer 32

- aggregates of lymphocytes; B cells form central follicle surrounded by T cells & macrophages surrounded by T cells & macrophages - have efferent lymphatics that drain into mesenteric lymph nodes, but lymph nodes, but no afferentno afferent lymphatics lymphatics - covered by specialised lymphoepithelium consisring of M cells (microfold) - g in gut enters via M cells that selectively take up particles & deliver them to lymphoid follicles also by particles & deliver them to lymphoid follicles also by specialised dendritic cells which ‘reach’ into the gut specialised dendritic cells which ‘reach’ into the gut lumen

Question 33

describe BALT

Answer 33

mostly B cells organised into aggregates & follicles with few germinal centres, some M cells but organisation is less germinal centres, than GALT - cont capillaries, arterioles, venules, HEVs and efferent lymphatics - suggests BALT may play role in sampling Ag not only from lungs but also from systemic circulationonly from lungs but also from systemic circulation - greater infiltration of white blood cells following infection (inducible BALT or iBALT)infection (inducible BALT or iBALT)

Question 34

what are the professional antigen presenting cells

Answer 34

dendritic cells (DC), macrophages, and B cells