Flashcards in Lymphatics & Regulation Deck (17):
What is a lymphoid follicle?
-an island of follicular dendritic cells within a sea of B cells
-located in all secondary lymphoid organs
Whats the difference between antigen presenting dendritic cells and follicular dendritic cells?
-dendritic cells are produced in bone marrow, while FDCs take their place in the lympoid organs during embryogenesis
-Dendritic cells present to T cells via MHC, FDCs display antigen to B cells
How does a follicular dendritic cell become "decorated" with antigens?
-its receptors bind complement fragments
-picks up and retains the ospsonized antigen (can also retain invaders opsonized by antibodies)
Where are HEVs located?
Paracortex of the lymph node
Are dendritic cells a part of the innate or adaptive immune system?
Where are the T cells located in the lymph node?
Which part, light or dark, of a germinal center contains the proliferating B cells?
How do APCs and lymphocytes know where to go within a lymph node and when to go there?
-Follicular dendritic cells in a lymph node produce a chemokine called CXCL13
-Naive B cells are attracted to this chemokine
-if B cell finds its cognate, it downregulates CXCL13, and upregulates CCR7
-CCR7 detects a chemokine produced in region where activated Th cells and B cells meet
What cytokines does the Regulatory T cell produce? What do they do?
IL-10 binds to T cells to block co-stimulatory signals
Both restrain the immune system
What receptor does B7 on APCs bind to on Th cells (stimulatory or inhibitory)?
CD28 = stimulatory
CTLA-4 = inhibitory
*CLTA-4 works by antagonizing the CD28 activation signal within the T cell
Where is the CTLA-4 receptor kept on a naive T cell? When active?
-naive = kept inside cell
-When activated, CTLA-4 is moved to the surface of the cell
Which has a higher affinity for B7 on T cells, CD28 or CTLA-4?
CTLA-4 (1000x higher)
What do M cells do?
-enclose antigens of the intestinal lumen in endosomes
-transport antigens to Peyer's Patches
-concentrate the efforts of a Peyer's patch on potential pathogens
Describe dendritic cells in the spleen?
-inactive reside in marginal sinus
-take up foreign antigens or get infected by pathogens
-Display MHC I/II
-Once activated, travel to PALS where T cells have gathered
**Th cells activated by dendritic cells move from PALS to lymphoid follicles to activate B cells
What stimulates Th 17 cells?
-IL-6 in concert with TGF-beta
**remember, TGF-beta also stimulates Treg cells
What happens when Natural Killer cells die off after an infection has been battled?
-NK cells secrete IFN-gamma, which activates macrophages
-NK cells die, no more IFN-gamma to activate macrophages, so they simmer down