The Life of a B-Cell: Surveillance and Warfare Flashcards
What is the chance of a B-cell sensing its specific antigen in the periphery?
How long does it take for a B-cell to circulate through the body?
1/10^6
The total circuit time varies between 12 and 24 hours
What is a B-cell that has not seen an antigen called?
Naive or virgin mature B-cell
What is the path of the B cell when it enters the spleen or LN?
It transverses the T-cell zone toward the B-cell follicles
How long can a B-cells live while they are recirculating?
several weeks to a couple months
What type of pathogens does the spleen monitor for?
blood-borne pathogens
What type of pathogens does the lymph nodes monitor for?
tissue-derived pathogens (from liver, skin, brain, etC)
What type of pathogens does the MALT monitor for?
Pathogens entering via the mucosal portal
What type of pathogens does the GALT monitor for?
Enteric pathogens (including those in Peyer’s patches)
How many WBCs are there per microliter of blood?
4000-11,000
How many lymphocytes are there per microliter of blood?
1000-4000
What percent of all WBCs in blood are lymphocytes?
15-40%
What is the ratio of T to B cells in most secondary lymphoid organs?
2:1
What types of cells are found in the thoracic duct lymph?
- effector T cells
- memory B cells
- plasma cells
(very few naive lymphocytes)
What structure rejoins the lymph to the blood?
thoracic duct lymph rejoins blood circulation in the subclavian vein
How do naive lymphocytes gain access to the LN?
L-selectin on the lymphocyte binds to GlyCAM or CD34 on the HEV
After lymphocytes are activated in the LN or spleen, what happens to their cell surface molecules?
L-selectin is downregulated so the effector lymphocyte won’t reenter the LN or spleen.
VLA4 and LFA1 are upregulated to direct the lymphocyte to inflamed tissue
What homing receptor pair is most important for extravasation of lymphocytes from the LN to the target tissue?
What are the ancillary pairs?
VLA4/VCAM1 is most important
LFA1/ICAM and CD2/LFA3 are ancillary
What ligand/addressin is crucial for delivery of lymphocytes to the skin?
CLA
What ligand/addressin is crucial for delivery to the GALT (gut)
a4b7 integrin
What splenic structure serves the same function as the subcapsular sinus of the LN?
the marginal sinus
Where are primary B follicles located in the LN?
Where are they located in the spleen?
LN- cortex
Spleen- white pulp
Through what structure do naive lymphocytes enter the LN?
The spleen?
LN- through HEV in the paracortex
Spleen- through central arterioles in the PALS
Where are T cells located in the LN?
In the spleen?
LN- paracortex
Spleen- periarteriolar lymphoid sheath (PALS)
Where are plasma cells and macrophages located in the LN?
The spleen?
LN- medulla
Spleen- red pulp