The lymphoid system

Question 1

describe briefly the origins of lymphoid cells

Answer 1

haematopoietic stem cells
precursor lymphoid cells
-to thymus for t cell maturation
OR- to bone marrow for B cell maturation 
---> secondary lymphoid organs

Question 2

give the primary (2) and peripheral (5) components of the lymphoid system?

Answer 2

Central
bone marrow
Thymus

Peripheral
Lymph nodes
Spleen 
Tonsils
Epithelia lymphoid tissue
Bone marrow

Question 3

what are the main functions of the lymphatic system?

Answer 3

to return lymph to the circulation to maintain fluid homeostasis and prevent excess accumulation of fluid in the tissue

To filter lymph before it returns to the circulation and has interactions with immune component cells

Question 4

give 3 examples of conditions that occur when lymph fails to drain

Answer 4

Lymphoedema
Chylous Ascities
pulmonary oedema

Question 5

lymph nodes

• located where?
• normal size?
• function?
• how does lymph move within the system?
• where is lymph filtered in the node?

Answer 5

• along the course of lymphatic vessels
• up to 2.5cm
• blind ending vascular channels that collect fluid from tissues and return to blood stream
• passive movement of fluid with valves ensuring unidirectional flow
• within the node parenchyma , here interactions can occur between cells in the node and cells in the lymph

Question 6

Describe the role of the lymphoid system in immunity?

Answer 6

houses cells go the innate immune system
Traffic of APCs links innate and adaptive immune responses
seat of the adaptive immune response (specificity, inducible, memory, Enhanced secondary reaction)

Question 7

Name the different cell populations in a lymph node (7 types)
-name where 2 of these cells are located within the node?

Answer 7

Lymphocytes:
B cells- assoc with follicles & germinal centres, inter follicular, plasma cells in medulla
T cells- T helper cells, T cytotoxic cells
NK cells

Macrophages
antigen presenting cells
Dendritic cells

+ endothelial cells

Question 8

Enlarged lymph nodes

• Why might lymph nodes be enlarged?
• lymphadenopathy, give the 3 main causes and give examples for each)

Answer 8

-due to reactive process
neoplastic disorders (mets or primary)

-Local inflammation
infection
vaccination/trauma/dermatopathic

Systemic inflammation
infection
autoimmune/CT disorders

Malignancy
Haematological (lymphoma/leukaemia)
Mets

+sarcoidosis/castlemans disease

Question 9

What is lymphangitis?

Answer 9

inflammation of the walls of lymphatic vessels, often seen with superficial lesion infection

Question 10

Ddx in generalised lymphadenopathy?

-investigations

Answer 10

suggests systemic inflammatory process or widespread malignancy e.g. lymphoma/leukaemia

-Take FBC before doing biopsy- might be evident from blood what the Dx is

Question 11

what might the following cell response indicate in a lymph node:

• B cell predominant?
• Phagocytic?
• T cell predominant?

Answer 11

• auto immune or infection
• draining a tumour site
• Viral infections/drugs

Question 12

what kind of organ is the spleen?

• describe the weight and size of a normal spleen
• name the two key aspects of the spleen
• describe the vascular supply
• what happens when a spleen ruptures?

Answer 12

• a secondary lymphoid organ
• 150-200g and is impalpable unless substantially enlarged

-Diaphragmatic surface
Visceral surface

-Highly Vascular
supplied by splenic artery and drained by splenic vein (forms portal vein with SMV)

-considered a surgical emergency, a diseased spleen is more likely to rupture

Question 13

• describe the structure of the spleen (types of pulp and their function)
• what is the overall function of the spleen?

Answer 13

-encapsulated organ, parenchyma includes red pulp and white pulp

red pulp
sinusoids and cords
sinusoids- fenestrated, lined by endothelial cells, supported by hoops of reticulin
cords- contain macrophages and some fibroblasts and cells in transit (RBC, WBC, PC and some CD8+ T cells)

white pulp
peri-arteriolar lymphoid sheath (PALS) with CD4 cells
Also lymphoid follicles (can show reactive changes)
Antigens reach white pulp via the blood

-acts as a filter for the blood
detects, retains and eliminates unwanted foreign or damaged material
facilitates immune response to blood bourne antigens
carries out haemolysis of old RBCs and might undertake Haematopoiesis in marrow disease

Question 14

see pic on circulation within spleen

Answer 14

look at it pls

Question 15

splenic enlargement

• presentation
• give the triad of hypersplenism

Answer 15

-dragging sensation in LUQ
discomfort with eating
pain if infarction

-Triad of:
Splenomegaly
Fall in one or more cellular components of blood
correction of cytopenias by splenectomy

Question 16

Give the 6 causes of splenomegaly and give examples of each

Answer 16

Infection
EBV, Malaria, TB, Typhoid, Brucellosis, Leishmaniasis, Trypanosomiasis

Congestion
portal (hepatic cirrhosis, portal/splenic vein thrombosis/ Cardiac failure)

Haematological disease
Lymphoma/leukemia, haemolytic anaemia, ITP, Myeloproliferative disorders

inflammatory conditions
RA, SLE

storage diseases
Gaucher’s, Neimann-Pick disease

Miscellaneous
Amyloid, Tumours, cysts

Question 17

causes of hyposplenism

Answer 17

most commonly from splenectomy (need life long vaccination)
also Coeliac disease
Sickle cell disease
Sarcoidosis
Iatrogenic- non-surgical

Question 18

What are Howell Jolly Bodies?

Answer 18

They are RBCs with residual DNA that would normally be removed from circulation, they indicate hyposplenism