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Year 3 - Haematology > Structure & Function of Lymph Node and Spleen > Flashcards

Structure & Function of Lymph Node and Spleen Flashcards

1
Q

The lymph nodes and spleen are primary or secondary lymphoid structures?

A

Secondary (peripheral) lymphoid structures

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2
Q

What are the primary (central) lymphoid structures?

A

Bone marrow and thymus

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3
Q

What are the secondary lymphoid structures?

A

Tonsils
Adenoids
Peyer’s patches in intestines
Lymph nodes
Spleen

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4
Q

What are lymph nodes?

A

Encapsulated collections of lymphoid tissue, usually small ovoid/bean shaped up to 1.5cm

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5
Q

How can lymph nodes be organised?

A

Superficial node groups (e.g. in the cervical, axillary and inguinal regions)

Internal node groups (e.g. mediastinal, para-aortic)

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6
Q

How can superficial node groups and internal node groups be examined?

A

Superficial node groups - can be palpated

Internal node groups - can be viewed radiologically

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7
Q

What is lymphadenopathy?

A

Lymph node enlargement

Can be localised, wide spread or generalised

Peripheral or central (internal)

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8
Q

What are causes of lymphadenopathy?

A

Local inflammation
Systemic inflammatory processes
Malignancy
Others

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9
Q

What are local inflammation causes of lymphadenopathy?

A

Infection (some have typical features e.g. TB, toxoplasma, catch scratch disease)
Others - vaccination, dermatopathic

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10
Q

What are systemic inflammatory causes of lymphadenopathy?

A

Infection e.g. viral infections
Autoimmune / CT disorders

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11
Q

What malignant causes can cause lymphadenopathy?

A

Haematological - lymphoma / leukemia
Metastatic cancer

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12
Q

What other causes of lymphadenopathy exist?

A

Sarcoidosis
Kikuchi’s lymphadenitis
Castleman’s disease
IgG4 related disease

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13
Q

What is lymphangitis?

A

In cases of superficial infection, you may see red lines extending from an inflamed lesion

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14
Q

What can Virchow’s node suggest?

A

Suggests abdominal malignancy - stomach, gallbladder, pancreas, kidneys, testicles, ovaries, lymphoma, prostate

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15
Q

Why are sentinel lymph nodes important?

A

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

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16
Q

Describe flow of lymphatics

A

Node is surrounded by connective tissue capsule

Afferent lymphatics penetrate the capsule and drain into sub scapular sinus

Lymph from sub scapular sinus percolates through the node (cell traffic, interactions for immune response; allows antigenic material to interact with fixed lymphoid tissue)

Lymph enters medullary cords and sinuses

Sinuses merge at hilum and form efferent lymphatics

Lymph rejoins extra nodal lymphatic circulation

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17
Q

What are 3 important regions of lymph node microarchitecture?

A

Cortex
Paracortex
Medulla

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18
Q

What is the cortex in lymph nodes?

A

Nodules of B lymphocytes arranged in follicles (primary / secondary)

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19
Q

What is the paracortex in lymph nodes?

A

Mainly T lymphocytes
Forms interfollicular tissue which surrounds follicles and extends out and merges with medulla

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20
Q

What is the medulla of lymph nodes?

A

Cords and sinuses draining into hilum

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21
Q

What cells are in lymph nodes?

A

Lymphocytes (B and T cells, Natural killer cells)
Mononuclear phagocytes (macrophages), antigen presenting cells and dendritic cells
Endothelial cells

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22
Q

Describe the different B cells in lymph nodes

A

B cells:
- Those associated with follicles and germinal centres: follicle centre cells, mantle cells, marginal cells, plasma cells
- Interfollicular: post germinal centre B cells, plasma cells
- Plasma cells: mainly in medulla

23
Q

Describe T cells in lymph nodes

A

T helper cells, T follicle helper cells, T cytotoxic cells

24
Q

What marker is a B cell marker?

A

CD20

25
Q

What marker is a T cell marker?

A

CD3

26
Q

What are primary follicles?

A

Small quiescent lymphocytes; unstimulated

No germinal centre

27
Q

What are secondary follicles?

A

Activated follicles; reactive

Germinal centre

28
Q

What happens in a follicle?

A

Quiescent B cells are activated in response to antigenic challenge

Antigen-antibody complexes are captured by follicular dendritic cells (FDCs)
- FDCs are specialised antigen presenting cells; they are mesenchymal and form meshworks through the germinal centre

Antigens on FDCs are presented to naive B cells; T helper cells assist

29
Q

What are follicular dendritic cells?

A

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

30
Q

What is the dark zone of B cells?

A

Now the B cells are triggered to start dividing
Clonal expansion occurs
Cells proliferate, differentiate and undergo somatic hypermutation

Somatic hypermutation is what allows the immune system to adapt quickly to make antibody producing plasma cells and memory B cells
Up to a million times greater than the normal rate of mutations in the human genome
Affinity maturation
B cells with the increased antigen affinity go into the light zone
Otherwise, they apoptose

31
Q

What is a centroblast?

A

A proliferating B cell in the dark zone -> will differentiate into centrocyte

32
Q

What happens in the light zone?

A

Positive selection of B cells; cell division slows down

FDCs present antigens to B cells -> B cells bind and internalise the antigen

Antigen bound by MHC class II, presented to T cell -> allows T cell to help B cell on its journey

33
Q

Positively selected B cells go one of three ways, which are?

A

Reenter dark zone and keep proliferating (and expressing cMyc to regulate GC formation)

Differentiate into plasma cells

Differentiate into memory B cells

34
Q

What is a centrocyte?

A

B cell in light zone

Will become either memory B or plasma cell

35
Q

CD79a is a marker of what cell?

A

Pan B marker

36
Q

What does the medulla of a lymph node comprise?

A

Blood vessels
sinuses
Medullary cords - plasma Cells, B cells, macrophages
Medullary sinuses - histiocytes, reticular cells

Lymph then drains into efferent vessels

37
Q

Reactive lymph nodes respond to?

A

A stimulus
some diseases have distinct reactive patterns

38
Q

What is sarcoidosis?

A

A granulomatous condition
Systemic disease

Sarcoid like reactions can also appear similar (may mask malignancy in a lymph node)

39
Q

Granulomatous inflammation has many causes. If caseous necrosis is present, what should we think is the cause?

A

Infectious cause (mycobacterial) until proven otherwise

40
Q

If there is stimulation of an immune reaction in a lymph node, what responses can occur?

A
41
Q

What does generalised lymphadenopathy suggest?

A

A systemic inflammatory / immunological process or widespread malignancy

42
Q

What are lymphomas?

A

Malignant tumours derived from cells of the immune system

43
Q

What are non-hodgkin’s lymphomas?

A

Most common form of lymphoma
Diverse group of diseases

B cell lymphomas
- Most common form of NHL
- Low grade and high grade forms

T cell lymphomas
- Less common
- More complex classification

44
Q

What are Hodgkin’s lymphomas?

A

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

45
Q

What is the spleen and where is it located?

A

One of the secondary lymphoid organs

Located high in left upper quadrant - normally not usually palpable

Two key aspects:
- Diaphragmatic surface
- Visceral surface: left kidney, gastric fungus, tail of pancreas, splenic flexure of colon

46
Q

What supplies the spleen?

A

Supplied by the splenic artery (branch of coeliac trunk) and drained by splenic vein (with sup. mesenteric vein forms portal vein)

47
Q

Describe the structure of the spleen

A

An encapsulated organ
Parenchyma includes red pulp and white pulp
Red pulp contains sinusoids and cords
Sinusoids are fenestrated, lined by endothelial cells and supported by hoops of reticulin

Cords contain macrophages and some fibroblasts and cells in transit (RBC, WBC, PC and some CD8+ T cells)

Fulfills same function for blood as lymph nodes do for lymph fluid (acts as filter for blood)
- Detect, retain and eliminate unwanted, foreign and damaged material
- Facilitate immune responses to blood borne antigens

48
Q

Describe the red pulp of the spleen

A

Connective tissue (cords of bilroth) and sinusoids engorged with blood (hence why its red)
Makes up around 3/4 to 4/5 of spleen
Cords contain lots of monocytes
Generally lots of WBCs and erythrocytes

49
Q

What does the white pulp comprise?

A

The periarteriolar lymphoid sheath (PALS) - CD4+ lymphoid cells

This is expanded by lymphoid follicles - B cells; may show reactive changes as in lymph node

Antigen reaches white pulp via the blood

When stimulated by antigens; T and B cell responses may occur

50
Q

What are causes of hyposplenism?

A

Most common - splenectomy
Others: coeliac disease, sickle cell disease, sarcoidosis

51
Q

What are red blood cell features of hyposplenism?

A

Howell jolly bodies - basophilic nuclear remnants often seen with decreased splenic function

52
Q

What are causes of splenomegaly?

A
53
Q

What are clinical symptoms of splenic enlargement?

A

Dragging sensation in LUQ
Discomfort when eating
Pain if infarction

54
Q

What is hypersplenism?

A

Splenomegaly
Fall in one or more cellular components of blood (cytopenias)
Correction of cytopenias by splenectomy

Year 3 - Haematology (35 decks)

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