Adaptive Response - where and when? Flashcards
Where are most immune responses initiated in?
secondary lymphoid organs
What do lymphocytes do once produced?
Travel around body in blood and lymph to meet Ag
What are HEV?
High endothelial venules - small blood vessels in lymph nodes that have different structure to other venules
How does cell decide to go to lymph node or not?
Afferent leads to lymph node, if Ag there - stay, if not leave
Lymph node structure”
Medulla paracortex and cortex
Where are B and T cells found in lymph node?
B cells cortexT cells paracortex
What do lymphocytes do if they meet Ag in lymph nodes?
Start dividing and form primary and secondary follicles
Where is the germinal center?
Within secondary follicle
What does dendritic cell usually do (resting to active):
Sits in tissue until meets pathogen. Uses PRR, and engulfes pathogen (phag). Then processes it and moves out to lymph node. No longer Phag but very potent APC with lots of MHCII and B7. Interacts with T cell in lymph node. If cytotoxic T cell - get activated and go to area of infection.
What do germinal centers contain?
B, T (fh), DC, FDC, Macrophages
Germinal centers are sites of 4
B cell class switch, affinity maturation, memory cell generation, Plasma cell precursor generation
Direction of travel in germinal center:
Not definite but:Naive B cell moves from dark zone to basal light to apical light to mature into plasma and memory cells
What cell in the secondary lymphoid used to show Ag to BCR?
FDC- more efficient
What do Tfh cells do in secondary lymphoid?
Help T cells differentiate
Why don’t B cells become plasma cells in GC?
produce lots of Abs and cover up all the Ags
What does the spleen usually deal with? vs lymph?
Spleen usually deals with blood infectionsLymph node usually deals with tissue infections
What are PALS?
T cell area of white pulp of spleen
So are PALS only T cells?
No, they also have follicles with marginal zones and mantle zones containing B cells, in the middle of which you get GC
What Ig protects mucousal surfaces? How?
IgA - very important in protecting mucousa.Stops adhesion of pathogens onto mucousal surfaces