Immune Cells and Organs Flashcards
ft. her majesty the spleen
What is a primary lymphoid organ?
Organ where lymphocytes are produced by lymphopoiesis.
What are the primary lymphoid organs?
Thymus and bone marrow
What is a secondary lymphoid organ?
Where lymphocytes interact with antigens and each other
Name 3 secondary lymphoid organs
Her Majesty the Spleen
…Lymph nodes
Mucosal associated lymphoid tissues (MALT)
Describe the structure of the thymus
2 Lobes divided into lobules by septums
What is the thymus packed with?
Maturing/proliferating T-lymphocytes
What is the change in the thymus during infection?
No obvious changes
How does thymic output change with age?
Output of NEW T cells decreases
What is the change in the bone marrow during infection?
Increased white cell production
Visible change
What are the sites of haematopoiesis in a foetus?
All bones, liver and spleeeeen
What are the sites of Haematopoiesis in an adult?
Flat and large bones (No liver and spleen)
What is the primary function of Lymph nodes?
To filter antigens present in the lymph
How does lymph enter and leave a lymph node?
Through the afferent (many) leaves through the efferent (one)
What are the cells present on the outside of a lymph node?
B cells in follicles
What happens to the B cells in the nodes when an immune response is in progress?
They proliferate and produce antibodies in the germinal centres of the node
Where are the T cells in a lymph node?
Further in from B cells, closer to the medullary sinus.
They tend to be closer to the sinuses than b cells
What changes are seen in lymph nodes during an immune response?
Enlargement
What other cells are present in the lymph nodes, and what do they do?
Macrophages engulf passing through pathogens
What is a high endothelial venule?
Specialised area of artery with thick endothelium that causes T/B cells to leave circulation and enter lymph node.
Does the spleen have High endothelial venules (HEVs)?
Nope, just lymph nodes
What is the purpose of Her majesty the Spleen?
To filter antigens present in blood
What is the spleen comprised of?
Red pulp: Erythrocytes present
White pulp: Lymphocytes present
What are the 3 parts of the white pulp of the spleen, and which cells do they contain?
Primary follicles: B-cells
Periarterial Lymphatic Sheath (PALS): Surrounds arteries contains T-cells.
Marginal zone: Between white pulp and red
Describe the immune system in the villi of the Gut
Interepithelial cells present on villi. Contains lymphatic drainage to mesenteric lymph nodes.
What is beneath the specialised mucosal epithelium in the gut?
Payer’s Patches - Contain large aggregates of lymphocytes/follicles which drain to mesenteric lymph nodes
What is the function of the specialised mucosal epithelium in the gut?
Contains microfold cells which sample antigens in the gut to pass to the payer’s patch to allow for surveillance.
Describe the immune system in the skin
Cutaneous immune system contains intraepidermal lymphocytes that drain through epidermal lymph vessels. Epidermal langerhans (dendritic cells) capture and present antigens and migrate to lymph nodes
Describe the recirculation of lymphocytes
Naïve lymphocytes produced in primary tissues, enter blood and circulate between blood and secondary tissues until reaction or death
What is Extravasation of T cells?
The migration of naïve T-cells from blood into lymph vessels
Describe the process of Extravasation of T-cells
- Naïve T cells roll along the endothelium until they reach the HEV.
- Selectin on the T cell binds to endothelial CD34 (weakly)
- Chemokines on the HEV bind to receptors on T cell, causing T-cell’s integrin to become high affinity binding form.
- Intergrin binds to Intracellular adhesion molecule (ICAM) immobilising the T cell, so it can move into the tissue.
What are clusters of differentiation?
Internationally recognised systematic nomenclature for cell surface markers that differentiate between haematopoietic cells
What are lymphocytes?
Small cells, w/ agranular cytoplasm and large nucleus.
Which cells are antigen presenting cells?
B-cells
Dendrite cells
Activated macrophages
