Lymphoid Tissues Flashcards
1
Q
Describe the 3 types of tissues surveyed
A
- circulating ‘sentinel’ immune cells: antigen presenting cells
- tissue resident cells: tissue macrophages, non-immune cells
- specialised lymphoid tissues: lymphatic organs, lymph nodes
2
Q
Describe lymphatic vessels
A
- contains lymph fluid
- connected throughout the body
- drains interstitial fluid and lymph from peripheral tissues back to circulation
- interlinked with circulatory system to allow for free movement from circulatory to lymphatic and vice versa nearer the heart
3
Q
Describe peripheral tissue drainage
A
- interstitial fluid and immune cells drain from tissues into lymphatic capillaries
- these intertwined with blood capillaries
- lymphatic capillaries -> lymphatic vessels -> lymph nodes -> circulation
4
Q
Describe the immune responses in lymphoid tissues
A
- sampling of peripheral tissues
- enables efficient specific immune responses via lymphocyte activation
- brings together sentinel immune cell, pathogen and adaptive immune cells
5
Q
Describe the primary lymphoid organs
A
- supports differentiation, proliferation and maturation of stem cells into immunocompetent cells
- location of immature lymphocyte development
- bone marrow, thymus
6
Q
Describe bone marrow
A
- origin of blood cells and location of initial B cell development - rest in spleen
- RBC, myeloid cells, lymphocytes
- positive and negative selection (BCR, self-antigen)
7
Q
Describe the thymus
A
- location of T cell development
- located in upper thoracic cavity - behind sternum, between lungs
- progenitor T cells from bone marrow migrate to thymus in early life
- thymocytes interact with epithelial cells within thymus to develop
8
Q
What are thymocytes?
A
T cell progenitors
9
Q
Describe T cell development
A
- thymocytes enter thymus via blood vessels
- undergo series of positive selection (cortex) and negative selection (medulla)
- selection involves MHC molecules and self-antigens
10
Q
Describe secondary lymphoid organs
A
- enable interaction between cells from circulatory systems and the lymphatic system
- primary site of specific immune responses
- spleen, lymph nodes, mucosa associated lymphoid tissues (MALT)
11
Q
Describe how secondary lymphoid organs enable interaction between cells from circulatory systems and the lymphatic system
A
- lymphocytes enter from blood via high endothelial venules (HEV)
- antigen presenting cells enter from lymph (afferent lymphatics)
12
Q
Describe the spleen
A
- functions as RBC filter, removing old cells - occurs in red pulp
- serves as site of B-cell maturation - occurs in white pulp
- white lymph nodes primarily filter lymph, spleen only filters blood
- contains antigen presenting cells in marginal zone of white pulp
- contains lymphocytes - resides in lymphoid sheath
13
Q
Describe the sections of the spleen where each cell is matured
A
- structure of white pulp encourages immune cell interactions
- central artery - blood access
- lymphoid sheath - t cells
- germinal centre - b cells
- marginal zone - dendritic cells and macrophages
14
Q
Describe the lymph nodes
A
- highly organised structure - similar to spleen
- filters lymph from peripheral tissues
- lymphocytes from blood can enter via HEV
- sites of specific immune responses
- formation of antigen specific T and B cells
- naïve lymphocytes circulate through nodes via chemokines CCL19 and CCL21
- B cells maintained in cortex via CXCL13 expression on stromal cells
15
Q
Which specific immune responses occur in the lymph nodes
A
- antigen presenting cells interact with T Cells
- specific T cells proliferate and interact with B cells
- specific B cells proliferate and generate plasma & form germinal centres
