Lecture Four; Components of the immune system 2 Flashcards
List the primary and secondary lymphoid organs;
1) Bone marrow and Thymus
2) NALT SALT (Skin) BALT (bronchus) GALT (payers patches, appendix) Lymph nodes
Describe drainage of lymph into the blood
Rest of body -> Thoracic duct -> Left subclavian vein
Top right quadrant -> Right subclavian vein
Describe DC function in lymphoid organs;
DC take up antigens from the blood and present them to naive T and B cells.
During central tolerance what can happen if a B cell is self reactive?
Immunoglobulin/receptor gene can be rearranged and the receptor can be tested again. If it continues to self react then it is destroyed.
What is a lymphoid tissue?
A tissue in which lymphocytes are found
What are lymphoid tissues usually?
Lymphoid tissues are usually groups of follicles that are surrounded or encapsulated by specialised supporting tissues or membranes.
Describe B cell arrangement in lymph nodes;
B lymphocytes are localized in the follicles
Describe t cell organization in lymph noes;
T lymphocytes are more diffusely distributed in the surrounding paracortical areas
What is also found in B cell follicles?
Follicular DC that distribute antigens between neighbouring follicles
What happens if a B cell in a follicle becomes activated?
The rest of the B cells move to the edge of the follicle
What occurs at the center of some B cell follicles?
B cell follicles contain germinal centres where B cells undergo intense proliferation after encountering their specific antigen and their co-operating T cell.
Describe Th and B cell interplay.
B cell with antigen receives signals from Th (reassurance) which allows it to undergo proliferation
Describe B cell and its changing follicular structure in lymph nodes;
Primary follicle (naive B cells) - Activation of some B cells in presence of Th cells. Secondary follicle (has Mantle of naive B cells)
This forms a germinal centre
What happens in a germinal center?
Essentially describes the proliferation of activated B cells
- Can be divided into light and dark regions.
Starting in the dark region;
- activated B cell forms proliferating centeroblasts
- These undergo somatic hypermutation (receptors gain high affinity)
- These centerocytes migrate to the light center where they undergo negative selection, those that self react are phagocytosed my macrophages.
- Those that dont self react, differentiate into memory cells and plasma B cells.
What are some extra features of lymph nodes that were not mentioned previously;
- Medullary sinus
- Medullary cords (macrophages and plasma cells)
- Marginal sinus (surrounds lymph node)
Describe the spleen;
- Fist sized organ
- Collects antigen from blood
- Disposes of senescent RBC
