Immune Cells and Organs Flashcards
What is a primary lymphoid organ? What are they?
Where lymphocytes are produced, bone marrow and thymus
What is the production of lymphocytes called?
Lymphopoiesis
What is is a secondary lymphoid organ? What are the secondary lymphoid organs? (4)
Where lymphocytes interact with antigens and other lymphocytes. Spleen, lymph nodes, mucosal associated lymphoid tissue (MALT), nasal associated lymphoid tissue (NALT)
Overview of lymphocyte life cycle
Mature in primary lymphoid tissue, enter circulation, leave circulation and enter secondary lymphoid tissue and keep recirculating till they meet their antigen or die.
How can defects in primary lymphoid tissue be treated?
Stem cell transplants
Where is the thymus?
Below the thyroid gland
How many lobes does the thymus have
Two, bi-lobed
Where do regulatory T lymphocytes develop in the thymus?
Hassall’s corpuscles
Affect of age on T cell output?
Same number of T cells, lower diversity
As lymph fluid drains in what part of the lymph node does it come into contact with first?
The lymphoid follicles (mostly B cells)
What are lymphoid follicles made up of primarily?
Mostly B cells
Where do T cells tend to be in the lymph nodes?
Towards the inside
When do germinal centres appear?
During an immune response
What are germinal centres?
Rapidly proliferating lymphocytes (B I think)
What are high endothelial venues (HEV)?
Where lymphocytes leave the circulation and enter the lymph node
What do chemokine do?
Direct lymphocytes
What do dendritic cells do?
Migrate through the lymph to the lymph nodes where they present antigens to the lymphocytes
What is the primary purpose of the spleen?
To filter for antigens in the blood
What is “white pulp” of the spleen?
Where lymphocytes are
What brings blood into the spleen?
The splenic artery
What is the periarterial lymphatic sheath? What lymphocyte is predominantly in it?
The space immediately adjacent to the splenic artery. T lymphocyte.
What is adjacent to the per arterial lymphatic sheath? What form is it in?
The B cell area in follicles
What susceptibility does a lack of spleen induce?
Infections with encapsulated bacteria
What do germinal centres in the spleen indicate?
Infection
What is a Peyer’s patch? Where is it found?
Large aggregates of lymphocytes and is found in the gut associated lymphoid tissue. Contains germinal centres and are predominantly B cells.
What is an M cell, where is it and what does it do?
It is a microfold, it is in the mucosal epithelium of the gut and samples antigens from the gut and delivers these antigens to the lymphocytes in the Peyer’s patch.
In the Peyer’s patch, are B or T cells on the interior / exterior?
B cells are in the middle, T cells are the most outermost
Whats are langerhans cells?
Dendritic cells of the skin and mucosa
What do keratinocytes do?
Detect damage in the skin and secrete signalling molecules to communicate this
Summarise what happens when a pathogen invades the epidermis
A dendritic cell will capture the pathogen and migrate to a lymph node and the appropriate lymphocytes will have to enter the lymph node to detect the antigen
What can high endothelial venules (HEV’s) do?
Arrest lymphocytes
What guides a lymphocyte to the right high endothelial venule?
Chemokines
Explain how T lymphocytes enter the HEV with reference to chemokines, integrin, ICAM1 and selectins
Selectins ensure a low affinity binding as the T lymphocyte rolls along the surface of a HEV. If a chemokine is present, this binds to the integrin on the lymphocyte changing its conformation. This causes a change to high affinity binding of the integrin to a molecule called ICAM1. This stops the rolling and the lymphocyte migrates into the tissue.
What type of cell expresses CD3?
T cells
What CD do all T cells express?
CD3
What is CD3?
An integral part of the non variable part of the antigen specific receptor on T cells.
What are the two types of T cell receptor and their relative percentages in the body?
Alphabeta (90%) and gammadelta (10%)
What two CD types can alphabeta TCR’s be split into and their proportions in the body?
CD4 (2/3) and CD8 (1/3)
What are CD4 cells and what do they do?
T helper cells, regulatory T cells that secrete cytokines
What are CD8 cells and what do they do?
Cytotoxic T cells, they lyse infected cells and secrete cytokines
When can a T cell recognise an antigen?
Once it has been processed and presented on the surface of another cell using an MHC molecule
What CD classes do B cells express?
19 and 20
What MHC class do B cells express?
II
What interaction do B cells and CD4 cells have?
B cells present their antigens to CD4 cells
What effector function do B cells have?
Producing antibodies
Can B cells recognise damaged antigens?
No
Difference between B and T cell antigen recognition?
B cells do not have to have processed antigens presented to them
What are the three APC’s of the body?
Dendritic cells, B cells, and macrophages
Whats special about follicular dendritic cells?
They present their antigen to B cells, only cells to do so
Where are B cells predominantly found?
In the lymphoid tissue
