Anatomy of immune system - lymph node focus Flashcards
Where do superficial lymphatic vessels drain from?
Subcutaneous and mucous membranes
Where do deep lymphatic vessels drain from?
Deep territories (accompany the arteries and deep veins)
What does the superficial and deep lymphatic vessels form when they converge?
Lymphatic trunks
What does the lymphatic trunk converge to?
Thoracic duct
Right lymphatic duct
Where does the thoracic duct collect lymph from?
Subdiaphragmatic regions and left supradiaphragmatic half
What does the thoracic duct flow into?
The junction between the left subclavian vein and the left jugular vein (base of neck)
What does the right lymphatic duct drain?
The right half of the body above the diaphragm
Where does the right lymphatic duct exit?
At the right jugular junction
What is the process of homing?
Mature naive lymphocytes entering different secondary lymphoid organs randomly from the blood
If not activated (or quiescent) through where do the lymphocytes leave?
The efferent lymphatic vessel
What does the lymph node promote?
Passage of lymphocytes from blood to lymph
Encounter between lymphocyte and antigen
Activation, proliferation and differentiation of B and T cells
Cooperation between T and B cells
3 regions of lymph nodes
Cortical region/B area
Paracortical region/T area
Medullary zone
Where are the germinal center of the lymph node found?
Secondary follicle of cortical region
Cells found in the cortical region of lymph nodes and their function there
B cells - inactive in primary follicles and active in secondary follicle
FDC - germinal centers, APC to B cell
Macrophages - APC to lymphocytes
How do FDC bind immune complexes?
Have receptors like CR1 (complement receptor 1) that binds C3b and FC receptor that binds antibody
Where in the lymph node are T cells activated?
Paracortical region
Cells found in the paracortical region of lymph nodes and their function there
T cells - mostly CD4+ but also some CD8+, activated by APC
DC- APC for T cells
Macrophages
In which region are the High Endothelial Venules (HEV) located?
Paracortical region
What is the function of HEV?
Allow for naive lymphocytes to leave the blood stream and enter the lymph node
Where in the lymph node are plasma cells found?
Medullary zone
Life span of plasma cell
1 month before undergoing apoptosis
Cells found in the medullary zone of lymph nodes and their function there
Plasma cells - medullary cords, secrete antibodies
Macrophages - medullary sinuses, phagocytosis and APC
DC - medullary sinuses, APC to T cells
Lymphocytes, mainly B cells - medullary cords
Neutrophils (sometimes) - medullary sinuses, fight bacteria via phagocytosis and degranulation
How many efferent and blood vessels in lymph node?
1 of each
How does the venues of the lymph node allow for the passage of lymphocytes?
It is modified to be isoprismatic
How does the antigen get to the lymph nodes?
It is transported as a soluble protein from lymph or carried by DC
2 zones of the germinal centers
Dark zone
Light zone
What is the dark zone occupied by?
Centroblasts
What happens to the centroblasts in the dark zones?
They proliferate and move into the light zone, transforming into centrocytes
What is the light zone occupied by?
Centrocytes that have migrated from the dark zone
What do the centrocytes in the light zone give rise tp?
B lymphocytes (both memory and plasma)
How many of the of the B cells stay in the lymph node and how many migrate to the bone marrow?
10% stay in the lymph-node
90% migrate to the boned marrow
What do reticular cells/reticular fibroblasts do?
Form a specialized network of fibers (FRC conduits or ducts) that structure the lymph node and facilitate immune function.
Where in the lymph node are FRC ducts found?
Primarily in paracortical region and also regions involved in antigen transport
Which form does the B cell recognize antigen in?
Native form
How many lymphocytes pass through the lymph nodes every day?
25x10^9 lymphocytes (each lymphocyte passes through a lymph node at least once a day)
When do naive T cells encounter antigens?
During passage through secondary lymphoid organs
How does the T cells reenter the blood stream?
They leave the lymph node through the efferent lymphatic and thoracic duct which empties into the superior vena cava which enter the heart
What regulates the exit of T cells from lymph nodes?
Interaction between S1P (sphingosine-1-phosphate, gradient of it as it is in low levels in lymphnode) and S1P1 (the receptor)
2 main zones of the spleen
Red pulp
Whte pulp
What is the red pulp?
Complex system of blood vessels that facilitate removal of old or damaged blood cells from circulation (emocateresis)
What is emocatersis?
Removal of old or damaged blood cells from circulation
What is the white pulp?
Region that contain T cells, B cells and accessory cells
Builds immunological response to blood antigens
