The Lymphoid System Flashcards
Where does B cell maturation occur?
Bone marrow
Where does T cell maturation occur?
Thymus
What are the primary lymphoid tissues?
Bone marrow
Thymus
What are the secondary lymphoid tissues?
Lymph nodes Spleen Tonsils (waldeyer's ring) Epithelio-lymphoid tissues Bone marrow
What is the function of the lymph system?
Fluid haemostasis
Prevents excessive accumulation of fluid in tissues
Permits cell traffic and trapping
Allows for interaction of cells and molecules with immune cells
What are lymph nodes?
Small oval bodies, up to 2.5cm in size
What is located along the course of lymphatic vessels?
Blind ending vascular channels that collect fluid from tissues and return it to the blood stream
Passive movement of fluid
Valves ensure direction of flow
What is the role of afferent channels in lymph nodes?
Drain lymph through capsule into the peripheral sinus
Where will lymph drain to from the lymph nodes?
Cisterna chyli/ thoracic duct
Left jugular, subclavian or bronchomediastinal trunks
Right jugular, subclavian or bronchomediastinal trunks
How will lymph go from the lymphatic system to the venous system?
Thoracic angle; junction of L/R subclavian and jugular veins
Where do arterial and venous vessels that serve the node enter/exit?
Hilum
What is lymph filtered through before it returns to the blood stream?
Lymph node parenchyma
How does the lymphoid system act as a defensie system?
House cells of innate immune system
Traffic of APCs links innate and adaptive immune responses
Allows for specificity, inducibility, memory and an enhanced secondary reaction
Where can B cells be found in the lymphatic system?
Follicles and germinal centers
Interfollicular
Plasma cells in the medulla of lymph nodes
What cell populations are found in lymph nodes?
B cells T cells NK cells Macrophages Dendritic cells Endothelial cells
What is CD20 a marker of?
B cells
What is CD3 a marker of?
T cells
What can cause local lymphadenopathy?
Infection; TB, toxoplasma
Vaccination
Dermatopathic
What is dermatopathic lymphadenopathy?
A distinctive reaction pattern in lymph nodes characterized by paracortical hyperplasia composed of dendritic cells, Langerhans cells, macrophages containing melanin pigment, and T-cells
What can cause systemic lymphadenoapthy?
Infection; viral Autoimmune Sarcoidosis IgG4 related disease Castelmans disease
What can cause malignant lymphadenopathy?
Haem; lymphoma/ leukaemia
Metastatic
What is sarcoidosis?
Granulomatous disease
Can mask malignancy in a lymph node
What is lymphangitis?
Superficial infection that tracts in lymph system
What can superficial lymphadenopathy be the first sign of?
Malignancy
What does generalised lymphadenopathy suggest?
Systemic inflammation or widespread malignancy
If you suspect lymphoma/ leukaemia due to generalised lymphadenopathy, what should you do?
Check the FBC
How can you differentiate a lymph node enlargement from a reactive process and a neoplastic process?
Reactive; different patterns
Neoplastic; filtration function hampered
Primary
Look at B cell response and T cell response separately
What does a predominant B cell response in lymph node enlargement suggest?
Autoimmune conditions
Infections
What does a predominant phagocytic response in a lymph node enlargement suggest?
Drainage of tumour site
What does a predominantly T cell response in a lymph node enlargement suggest?
Viral infection
Drugs; phenytoin
Where is the spleen located?
Left upper quadrant
Diaphragmatic surface
Visceral surface; left kidney, gastric fundus, tail of pancreas, splenic flexure of colon
What supplies the spleen?
Splenic artery (branch of coeliac axis) Draine by splenic vein (joins with SMV to form portal vein)
Is the spleen encapsulated?
Yes
What is contained within the spleen parenchyma?
Red pulp
White pulp
What does red pulp contain?
Sinusoids and cords
Describe the sinusoids in the spleen
Fenestrated
Lined by endothelial cells
Supported by hoops of reticulin
What do the cords of the spleen contain?
Macrophages
Fibroblasts
Cells in transit; RBC, WBC, PC, CD8+ T cells
What is the function of the spleen?
Filter for blood
Detects, retains and eliminates unwanted foreign or damaged material
Facilitates immune responses to blood borne antigens
What does the white pulp of the spleen contain?
Periarteriolar lymphoid sheath (PALS) = CD4+ T cells
Expanded by lymphoid follicles in reactive changes
How do antigens reach the white pulp of the spleen?
Blood
APCs in white pulp will present antigen to immune reactive cells
when stimulated by antigen, T c and B cells respond
What are the symptoms of splenic enelargement?
Dragging sensation in LUQ
Discomfort with eating (pressure on gastric fundus)
Pain if infarction
Hypersplenism
What is the triad of hypersplenism?
Splenomegaly
Fall in one of more cellular components of blood
Correction of cytopenias by splenomegaly
What infections can cause splenomegaly?
EBV Malaria TB Typhoid Brucellosis Leishmaniasis Trypanosomiasis
What diseases can result in congestion and subsequent splenomegaly?
Portal:
Hepatic cirrhosis
Portal/ splenic vein thrombosis
Cardiac failure
What haem disorders can result in splenomegaly?
Lymphoma Leukaemia Haemolytic anaemia ITP Myeloproliferative disorders
What inflammatory conditions can result in splenomegaly?
RA
SLE
What storage diseases can result in splenomegaly?
Gaucher’s
Niemann-Pick disease
Broadly, what can cause splenomegaly?
Infection Congestion Haem diseases Inflammatory conditions Storage disease Amyloid Tumours Cysts
What can cause hypersplenism?
Associated with splenomegaly
Key diagnostic feature of hypersplenism if splenectomy
What can cause hyposplenism?
Splenectomy Coeliac disease Sickle cell Sarcoid Iatrogenic
What causes the symptoms seen in hyposplenism?
RED pulp dysfunction; howell jolly bodies
