Structure and function of lymph node and spleen​

Question 1

Primary/central lymphoid structures

Answer 1

Bone marrow and thymus

Question 2

Secondary/peripheral lymphoid structures​ (2)

Answer 2

Lymph nodes and spleen

Other secondary lymphoid structures include tonsils/adenoids, Peyer’s patches in intestine

Question 3

Lymph Nodes ​(5)

Answer 3

Encapsulated collections of lymphoid tissue​

bean shaped​ + small (up to 1.5cm) but can become enlarged​
​
along the course of lymphatic vessels​

Groups of nodes drain particular territories​

Particular territories drain to specific node groups​
​

Question 4

Superficial node groups

Answer 4

e.g. in the cervical, axillary and inguinal regions can be palpated.​

Question 5

Internal node groups

Answer 5

e.g. mediastinal, para-aortic can be viewed radiologically​
​

Question 6

Lymphadenopathy

Answer 6

lymph node enlargement​

​localised, more wide-spread or generalised​
​
peripheral or central (internal)

Question 7

Lymphadenopathy causes (12)

Answer 7

Local inflammation​
=Infection (e.g TB,Toxoplasma, Cat scratch disease)​
=Others e.g. vaccinat, dermatopathic​

Systemic inflammatory processes​
=eg viral infections​
=Autoimmune / CT disorders​

Malignancy​
=Haematological​
=Lymphoma / Leukaemia​
=Metastatic​

Others​
e.g. Sarcoidosis, Kikuchi’s lymphadenitis, Castlemans Disease; IgG4 related disease​

Question 8

Lymphatic Drainage​

Question 9

Regional Lymphadenopathy​ (3)

Answer 9

superficial infection may see red lines extending from an inflamed lesion - lymphangitis​

superficial lymphadenopathy= first sign malignancy

identify primary lesion​=Virchow’s node​

Question 10

Sentinel Lymph Node (3)

Answer 10

The first lymph node to which cancer cells are most likely to spread

There may be more than one sentinel node

Identified by dye or radioactive isotopes​

Question 11

Lymph Node Anatomy​- direction of lymph flow

Answer 11

1. afferent lymphatic vessel
2. sub capsular sinus
3. trabecular sinus
4. medullary sinus
5. efferent lymphatic sinus

Question 12

Lymph node microarchitecture (3)

Answer 12

cortex= nodules of B lymphocytes arranged in follicles (primary / secondary)​

paracortex= mainly T lymphocytes​.
forms interfollicular tissue which surrounds follicles and extends out and merges with medulla​

medulla= cords and sinuses draining into hilum​

Question 13

Lymph Node Histology (4)

Answer 13

B cell follicle with germinal centre​

interfollicular tissue​

mantle zone​

marginal zone

Question 14

Cell populations in lymph nodes- Lymphocytes B cells (9)

Answer 14

Assoc w follicles + germinal centres​=
-Follicle centre cells​
-Mantle cells​
-Marginal cells​
-Plasma cells​

Interfollicular​
-Post germinal centre B cells​
-Plasma cells​

Plasma cells = mainly in the medulla

Question 15

Cell populations in lymph nodes- Lymphocytes T cells

Answer 15

-T helper cells​
-T follicle helper cells​
-T cytotoxic cells​

Question 16

Cell populations in lymph nodes- other (5)

Answer 16

Natural killer cells​

Mononuclear phagocytes (macrophages)

Antigen presenting cells

Dendritic cells

Endothelial cells​
​

Question 17

Follicles- P + S (8)

Answer 17

Primary​=
-Small quiescent lymphocytes​
-Unstimulated​
-No germinal centre​
​
Secondary​=
-Activated follicles​
-Reactive​
-Germinal centre​

Question 18

What happens in a follicle? (6)

Answer 18

Quiescent B cells are activated in response to antigenic challenge​

Antigen-antibody complexes are captured by follicular dendritic cells (FDCs)​=
-specialised antigen presenting cells ​
-mesenchymal + form meshworks thro germinal centre​
​
Antigens on the FDCs are presented to naive B cells =
-T helper cells assist​

Question 19

Follicular dendritic cells (4)

Answer 19

Mesenchymal origin​

Provide architectural support to germinal centres​

Facilitates debris removal through secretion of bridging factor​= macrophages come and gobble up debris​

Antigen capture for memory B cells​
​

Question 20

Dark zone (8)

Answer 20

B cells are triggered to start dividing​=
-Clonal expansion occurs​
-Cells proliferate, differentiate and undergo somatic hypermutation​
​
Somatic hypermutation allows the immune system to adapt quickly to make antibody producing plasma cells + memory B cells​

Million times greater than the norm rate of mutations in human genome​

Affinity maturation​=
-B cells with increased antigen affinity go into light zone​
-Otherwise, they apoptose​

Question 21

Centroblast (2)

Answer 21

Proliferating B cell in dark zone​

Will differentiate into centrocyte

Question 22

Light zone (6)

Answer 22

Positive selection of B cells​

Cell division slows down​
​
FDCs present antigens to B cells​, they bind + internalise the antigen​

Antigen bound by MHC class II, presented to T cell​

This allows T cell to help B cell on its journey​

Question 23

Centrocyte (2)

Answer 23

B cell in light zone​

Will become either memory B cell or plasma cell

Question 24

Medulla (7)

Answer 24

Blood vessels​

Sinuses​

Medullary cords​=
-Plasma cells, B cells, macrophages​
​
Medullary sinuses​=
-Histiocytes, reticular cells​
-Lymph drains into efferent vessels

Question 25

Reactive lymph nodes (2)

Answer 25

Response to stimulus​ Some diseases have distinct reactive patterns

Question 26

Sarcoidosis (3)

Answer 26

A granulomatous condition Systemic disease, requires clinical correlation​ ​ Sarcoid like reactions can also appear similar​- May mask malignancy in a lymph node​ ​

Question 27

Granulomatous inflammation (2)

Answer 27

has many causes​ when caseous necrosis is present infectious cause (Mycobacterial) until proven otherwise

Question 28

Generalised Lymphadenopathy (2)

Answer 28

Suggests a systemic inflammatory / immunological process or widespread malignancy​ ​ ​ Clinical and pathological knowledge are most useful in directing investigations​

Question 29

Lymphomas- Non Hodgkin’s Lymphomas (NHL)​ (6)

Answer 29

-Most common form of lymphoma​ B cell lymphomas​ -Most common form of NHL​ -Low+ High grade forms​ T cell lymphomas​ -Less common​ -More complex classification​

Question 30

Lymphomas- Hodgkin’s Lymphomas (4)

Answer 30

Less common than NHL​ Different types – classical and nodular lymphocyte predominant​ Also of B cell origin​ Usually has a very good prognosis​

Question 31

Spleen

Question 32

Structure of the Spleen

Question 33

Hyposplenism

Question 34

Splenomegaly