Lymphoid anatomy Flashcards
What are the primary lymphoid tissues and what happens there?
Thymus and bone marrow.
B and T cells develop there, Ag independent
What are the secondary lymphoid tissues and what happens there?
Lymph nodes, Spleen, MALT
Places where lymphocytes migrate to
What do lymphoid vessels contain?
lymph fluid, lymphocytes, tissue dendritic cells
How does lymph move?
Fluid-pressure
Lymphocyte activation process
- When infection occurs. free antigen and antigen-bearing dendritic cells travel from site of infection through the afferent lymphatic vessels.
- Go to draining lymph nodes.
- T and B cells are activated.
- Once activated they leave nodes via efferent lymphatic vessels into the blood then into the tissue.
How long can it take for a response if the antigen is new?
4-6 days
What is the secondary follicle in a lymph node?
Site of intense B cell proliferation in infection
What does the spleen do?
Filters antigen from the blood and enable us to respond to blood borne pathogens.
What are the two main adhesion molecules and what is their endothelial ligand?
Selectin (CD34) and Integrin (ICAM-1,2,3)
First Migration step.
- P-selectin is induced on vessels in response to inflammatory stimuli.
- TNF and LPS also induce E-selectin.
- Recognise sulphated sialyl-Lewisx structures on immune cells.
- Mediated reversible movement
- Rolling
Second migration step
- ICAM-1 and ICAM-2 are induced on vessels by e.g. TNF.
- Bind to LFA-1 and CR3 on leukocytes
- Rolling is stopped
- Firm attachment
Third migration step
- Leukocyte crosses endothelial wall- extravasation
- Involves LFA-1/CR3
What is CXCL8 released by and what does it do?
Released by macrophages and attracts neutrophils and mobilises naive T cells.
what is CCL2 produced by and what does it do?
Produced by epithelial and stroll cells. Attracts monocytes.
