L5 - Lymphoid anatomy Flashcards
What are the three anatomical requirements for an immune response?
- To enable rare antigen-specific lymphocytes to encounter their antigen
- To enable different types of antigen-specific lymphocytes (e.g. T cells and B cells) to make physical contact
- To enable cells to go where they are needed e.g. site of infection
The movement of cells - the two components
- Migration to a particular tissue/organ
- Movement within tissue/organ
What is the general state of lymphocytes?
Circulate the body ‘looking’ for antigens
How do you enhance the chances of rare antigen-specific T and B cells interacting with each other?
1 - Have collections of T cells and immune cells in sites where infection is likely to happen
2 - Have cells circulate throughout the body and have specialised sites of antigen capture where lymphocyte/antigen interactions are enabled
These both involve the continuous movement of lymphocytes through the blood and lymphoid system
Lymphoid organs: what types are there and what do they do?
Primary Lymphoid Tissues:
Where B and T cells develop, Ag-independent:
* Thymus
* Bone marrow
Secondary Lymphoid Tissues:
Where lymphocytes migrate to:
* Lymph nodes
* Spleen
* MALT (mucosa-associated lymphoma tissue)
Lymphoid vessels: are they blood vessels, what do they do, what do they contain, and what is the heart’s role in pumping the vessels?
Not blood vessels! (but similar)
Connect most body tissues with lymph nodes and eventually the bloodstream
Contains Lymph fluid, lymphocytes and tissue-dendritic cells
Lymph not pumped by heart muscles and valves
Lymphocyte activation: what is the process?
When infection occurs in a site (skin, etc), free antigen and antigen-bearing dendritic cells travel from the site of infection through the afferent lymphatic vessels -> draining lymph nodes -> T and B cells are activated (selection, differentiation, proliferation) -> Once activated leave nodes via efferent lymphatic vessels -> Then into blood -> Back to tissue
This may take 4-6 days if a new antigen is presented to the immune system
Lymphocytes interacting with lymph nodes
- Lymphocytes and lymph returns to the blood via the thoracic duct
- Naive T-cells enter the lymph nodes from the blood
- Antigens reach lymph nodes through lymph travel/dendritic cells
- In lymph nodes, Naive T-cells become activated after binding with dendritic cells containing antigens
Lymph system anatomy
Adenoids - back of nasal cavity lymphoid tissue Tonsils - throat/mouth lymph nodes
Right lymphatic duct - terminal lymph vessel
Right subclavian vein - feeds into RLD
left subclavian vein - feeds directly into TD
Thoracic duct - Returns lymph to systemic venous Spleen -
Appendix -
Peyer’s patches -
Lymph vessels -
Lymph nodes -
Thymus -
Heart -
Lymph node structure: the components and their roles?
Afferent lymphatic artery - Lymph enters the LN through this
Efferent lymphatic artery - Lymph exits the LN through this
High endothelial venule (HEV) - where Naive T-cells enter LNs
Primary follicle -
Secondary follicle - site of extensive B-cell proliferation
Collagenous capsule -
Cortex - key part of antibody response, germinal centres for b cells
Paracortex - T-cell area, where they become activated
Medulla - Contains plasma cells, T-cells, and macrophages
Hilus -
Artery - normal function
Vein - normal function
Medullary cords -
Trabeculae -
MALT: what is it, what different forms does it have, and what does it do?
Mucosal-associated lymphoid tissues
It contains as many lymphocytes as the rest of the body
- Gut-associated lymphoid tissue (GALT)
- Nasal-associated lymphoid tissue (NALT)
- Bronchus-associated lymphoid tissue (BALT)
Also, find specialised cells in the liver, reproductive tract, etc
GALT: what is it, where is it found, how does it interact with lymph nodes, and what does it do?
Gut-associated lymphoid tissue
Directly underneath the epithelia - Peyer’s patches
No afferent lymphatic, only efferent lymphatic vessels
- Big role in producing IgA antibodies using M cells to allow antibody transport across the gut membrane (? IM NOT SURE?)
- Take up antigens from the gut and allow immediate reaction to these antibodies (cells must still follow the efferent vessels and enter the bloodstream that way)
M cells
Contains dendritic cells, T-cells, and B-cells directly underneath them and M cells allow these cells to receive antigens immediately from the gut
The spleen: what is it, what does it do, how does lymph travel through it, and what are its key features?
Lymphatic organ
- Filters antigen from the blood
- Helpful in defending against blood-borne pathogens
- Recycle old, damaged red blood cells
Blood - splenic arteries - trabecular arteries - central arteries - arterioles - red pulps
Has no afferent lymphatics
The different pulps
Red pulp regions - filter red blood cells
White pulp regions - immune roles
