Lymphatics & Regulation Flashcards Preview

Term 3: Immunology/Pathology > Lymphatics & Regulation > Flashcards

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


What is Activation-induced cell death (AICD)?

-process by which obsolete T helper cells are eliminated

How it works:
-CTL's have Fas-L

-when T cells are activated, they become increasingly more sensitive to ligation of Fas proteins

-CTL's kill 90% of the obsolete active T cells