The Lymphoid System Flashcards
Where does B-cell maturation occur?
Bone marrow
Where does T-cell maturation occur?
Thymus
Where do haematopoietic stem cells come from?
Foetal liver
Postnatal bone marrow
Describe lymph nodes?
Small, oval bodies
Up to 2.5cm
How does lymph travel?
Through the capsule into the peripheral sinus
Where does lymph travel from the node to?
Leaving the hilum…
Cistema chyli/Thoracic duct
L jugular, subclavian + many more
In what is lymph filtered?
Node paranchyma
What are the 2 main functions of the lymph system?
Return lymph to the circulation - important in fluid homeostasis + prevents excessive accumulation of fluid in the tissues (oedema)
Filter lymoh before returning to the circulation - cell traffic + interactions with immune competent cells
What does the lymph system hep with regarding the adaptive immune response?
Specificity
Inducible
Memory
Enhanced secondary reaction
Describe lymphocytic B cells
Assoc. with follicles and germinal centres
Interfollicular
Plasma cells - mainly in the medulla
Describe lymphocytic T cells
T helper cells
T cytotoxic cells
What other immune cell is lymphocytic?
Natural Killer Cell
What other immune cells are present in lymph nodes?
Macrophages
Antigen presenting cells
Dendritic cells
Endothelial cells
What are causes for lymphadenopathy?
Local inflam
Systemic inflam
Malignancy
Others e.g. sarcoidosis, Castlemans disease
What is the main immune response for an autoimmune condition or infection?
B-cell
What is the main immune response for the draining of a tumour?
Phagocytes
What is the main immune response for viral infections and drug reactions such as from Phenytoin?
T-cell
What does generalised lymphadenopathy suggest?
A systemic inflam process or widespread malignancy
Describe the dimensions of the spleen?
High in the left upper quadrant of the abdomen
150-200g
12x7x3cm
What are anatomically related to the spleen?
Diaphragm Left kidney Gastric fundus Tail of pancreas Splenic flexure of colon
What is the blood supply and drainage of the spleen?
Splenic artery (Coeliac axis) Splenic vein with SMV forms of portal vein)
Describe the spleen?
Encapsulated organ
Parenchyma includes red pulp and white pulp
What does the red pulp contain?
Sinusoids
Cords
Describe the sinusoids?
Fenestrated
Lined by endothelial cells
Supported by hoops of reticulin
What do the cords contain?
Macrophages
Some fibroblasts
Cells in transit (e.g. RBC, WCC, PC and some CD8+ T cells)
What does the spleen do?
Detect, retain and eliminate unwanted foreign or damaged material
Facilitates immune response to blood borne antigens
Describe the structure of the spleen?
White pulp comprises the periarteriolar lymphoid sheath (PALS) - CD4+ lymphoid cells
Are antigen presenting cells in the red or white pulp?
White
What are features of an enlarged spleen?
Dragging sensation in LUQ
Discomfort with eating
Pain if infarction
What is the triad of hypersplenism?
- Splenomegaly
- Fall in one or more cellular components of blood
- Correction of cytopenias by splenectomy
Risks of what increase if you have splenomegaly?
Infection Congestion Haematological diseases Inflam conditions Storage disease Miscellaneous things e.g. tumours, cysts and amyloid
What are causes of hyposplenism?
Splenectomy Coeliac disease Sickle cell disease Sarcoidosis Iatrogenic
What is seen in red cells after a splenectomy?
Howell-jolly bodies
