LW - cells and tissues of the immune system Flashcards
What is the difference between primary lymphoid tissue and secondary lymphoid tissue?
Primary - site of development.
Secondary - site of an immune response.
What are 4 examples of primary lymphoid tissues? What is the function of each of them?
Bone marrow - B cells and T cells origin. Matures B-cells before export to a secondary lymphoid tissue. Site of some B-cell differentiation.
Ileal peters patch - Site of B-cell maturation. Found in the small intestine.
Bursa of fabricus - B-cell maturation in birds. Lymphoepithelial organ near the cloaca.
Thymus - site of T-cell development. Involutes with age.
What is the consequence of a bursectomy?
Removes the humeral immune response from a bird.
What is the consequence of a thymectomy?
Removes the cell mediated immune response.
What are 2 examples of secondary encapsulated lymphoid tissue? What is the function of each of them?
Lymph nodes - At primary follicles there are naive B-cells. At secondary follicles, the B-cells are activated. T-cells are found in the paracortex, which surrounds the follicles.
Spleen - No lymphatic drainage. Continuous with blood circulation. Secondary follicles contain activated B-cells. PALS (peri-arteriolar lymphoid sheath) contains T-cells.
Where is the Hassal corpuscle found and what does it produce?
In the thymus. It produces growth factor.
What is the structure of a secondary follicle found within the lymph nodes?
A germinal centre surrounded by the mantle zone.
What are examples of unencapsulated lymphoid tissue?
Mucosa associated lymphoid tissue (MALT):
- Gastrointestinal.
- Bronchial.
- Nasal.
- Conjunctival.
Peyer’s patch - domes in small intestine. Has B-cell and T-cell areas within a mesenteric lymph node.
What is the function of an m-cell?
Luminal antigen sampling.
What are small lymphocytes?
T or B cells. Virgin or memory - inactive. Little cytoplasm, large nucleus. Few organelles. Condensed chromatin.
What are lymphoblasts?
T or B cells.
Stimulated by antigen.
More cytoplasm and organelles.
Less condensed chromatin.
How can T-cells and B-cells be distinguished?
- Anatomical location.
- Function.
- Expression of surface molecules unique to each population.
Why do lymphocytes recirculate?
To maximise the chance of contact between an antigen and the appropriate responding populations of lymphocytes.
What is the role of dendritic cells in immune surveillance?
- Bind to the antigen on the bacteria.
- Migrates to t-cells so they can be activated.
- Allows for clonal expansion of T-cells.
- Recirculation
What is the definition of high endothelial venue?
Structural modification of venular endothelial cells such that they take on a cuboidal morphology, thus creating local turbulent flow to maximise the chance of interaction with leukocytes.
