What are primary (or central) lymphoid tissues?
Where lymphocytes develop
What are secondary lymphoid tissues?
Where the adaptive immunity response are initiated
Give an example of primary lymphoid tissue?
Bone marrow, thymus
Give an example of secondary lymphoid tissue?
Lymph nodes, Spleen, Mucosa-associated lympohd tissue (e.g.peyers patches, appendix, BALT)
What is a thymocyte?
An immature T cell that moves out tof the bone marrow and migrates into the thymus
How many lobes does the thymus have?
- It is bi-lobed.
Lobules are separates by connective tissue called what?
Trabeculae
Each lobule has an outer WHAT and inner WHAT?
outer cortex
inner medulla
What do nurse cells do?
They are involved in selecting thymocytes to ensure they are mature when they leave the thymus
The cortex is
a) loosely packed with cells
b) tightly packed with cells
b) tightly packed with cells
The medulla is
a) loosely packed with cells
b) tightly packed with cells
a) loosely packed with cells
The site of positive selection is
a) the cortex
b) the medulla
a) the cortex
The site of negative selection is
a) the cortex
b) the medulla
b) the medulla
Cd stands for what?
cluster of differentiation
Mature cells are all CD3+. True or false.
True
CD8 interacts with
a) MHC class 1
b) MHC class 2
a) MHC class 1
CD4 interacts with
a) MHC class 1
b) MHC class 2
b)MHC class 2
Immature T cells are CD3-, CD4- and CD8-. What is this state called?
Double negative thymocytes
Interaction with what causes the production of CD3, CD4, CD8 in T cells?
Cortical Epithelial cells and Dendritic cells
Immature T cells activated to express CD3, CD4 and CD8, following positive selection of cells in the thymus, are called what?
double positive thymocytes
CD4+ t cells are known as
helper T cells
CD8+ t cells are known as
cytotoxic T cells
What is an antigen?
Molecule that can be recognised by lymphocytes as foreign and has a defined shape.
Antigens are transported tot he lymph nodes by cells such as?
dendritic cells.
Bacteria can also be transported free
Lymph nodes are situated at sites prone to infection. True or False.
True
What are bean shaped structures which filter and trap antigen from the lymph.
Lymph nodes
Where in the lymph nodes do B cells get activated?
Cortex
Where in lymph nodes do T cells get activated?
Paracortex
What is the general name of how lymphocytes cross the endothelium?
rolling behaviour
In rolling behaviour L-selectin on the lymphocyte binds to what?
And with what affinity?
Either glycCAM-1 (proteoglycan) or CD34 on the high endothelial venial (HEV).
Low affinity
What is chemokine?
What does it do?
Chemokine is a chemoattractant cytokine which binds chemokine receptors on lymphocytes giving activation signal for adhesion molecule Ifa-1, which changes conformation and binds very tightly to ICAM-1.
What affinity is the interaction between ICAM-1 and Ifa-1 in rolling behaviour?
Very tight
What is the Germinal Centre?
The site where you get the proliferation of an activated B cell (releases b cells that differentiate into plasma cells into the lymphatic which leads to the blood stream)
What are lymphoid follicles?
A loose network of follicular dendritic cells (FDCs) in a region rich in B cells.
What is the difference between FDCs and DCs?
FDC are not leukocytes and are not derived from bone marrow precursors. They are also not phagocytic and do not express MHC class II proteins.
The spleen is composed of red and WHAT pulp?
red and white pulp
Is it the red or white pulp that acts as a lymph node?
white pulp
What happens in the red pulp?
- red blood cells disposed of
What is the structure of the white pulp?
Lymphocytes surround a central arteriole forming Periarteriolar Lymphoid Sheaths (PALS).
Primary follicles are attached to PALS where you get differentiating lymphocytes
MALT protects mucus membranes lining what?
digestive, respiratory and urogenital systems
BALT is a form of MALT. True or false
True
What is the function of MALT?
protects the gut
peyers patches are a form of what?
lymph nodes. They are a form of GALT
What is an M cell?
An M cell (microfold) is a specialised cell above the peyers patches which transportantigen from the gut into the lymphoid tissue
What are intraepithelial lymphocytes?
specialised lymphocytes that localise in the epithelial layer (they are able to leave and circulate also)
Naiive T cells have L-selectin which binds WHAT and alpha4beta7 which binds WHAT?
L-selectin binds GlyCAM-1
alpha4beta7 binds MadCAM-1
Cells activated in peyers patches have high/low a4b7 and high/low L-selectin.
cells activated in PPs have high α4b7 and low L-selectin which helps them re-enter the secondary lymphoid organ where they encountered Antigen
what does a4b7 do
Encourages localisation in mucosal tissue cell the first encountered the antigen
