Secondary Lymphoid Organs and Lymphocyte Trafficking

Question 1

where B and T cells are born and where T cells are educated

Answer 1

Primary lymphoid tissue: bone marrow + thymus

Question 2

where the recognition phase of the adaptive immune response occurs

Answer 2

secondary lymphoid tissue

- where cells get together to be instructed and mobilized in response to a threat

Question 3

secondary lymphoid tissues

Answer 3

• lymph nodes
• MALT
• spleen
• liver

Question 4

Lymphoid follicles

Answer 4

• central feature of all secondary lymphoid organs

- islands of FDCs in a sea of B cells

Question 5

T or F. Both DCs and FDCs both originate from the bone marrow

Answer 5

F! DCs = bone marrow; FDCs originate as do ‘regular’ cells but take up final position in secondary lymphoid tissue

Question 6

How do FDCs capture antigen?

Answer 6

• complement receptors on FDCs bind antigen decorated by complement early in the infection, then this is transported to the secondary lymphoid tissue
• Fc receptors on FDCs bind antigen captured by Abs later in infection

Question 7

the fate of B cells in the lymphoid follicle

Answer 7

• will die in the germinal centres unless they are ‘rescued’ by Th cells via CD40/CD40L interaction
• w/ T help, B cells will continue to proliferate and become plasma cells, leave the germ. center to the light zone of lymph follicle where they are tested, then migrate b/w dark and light zones as they undergo affinity maturation and Ab class switching

Question 8

common to all secondary lymphoid tissue except the spleen

Answer 8

high endothelial venules (HEVs)

- acts as the doorway for B/T cells to enter secondary lymphoid tissue from the blood

Question 9

‘dating bars’ for DCs, T cells, and B cells

Answer 9

lymph nodes

Question 10

how do antigens enter the lymph nodes?

Answer 10

• either as opsonized material waiting to be captured by the FDCs
• OR cargo in migrating DCs as peptides within the grooves of their MHCs

Question 11

where T cells tend to collect from blood

Answer 11

• paracortex

- where they meet up with DCs and get stimulated

Question 12

these are in the marginal sinus of the lymph node and cleans up or ‘filters’ the lymph this way

Answer 12

macrophages

Question 13

where B cells tend to collect from blood

Answer 13

cortex

- form here, B cells enter lymphoid follicles and interact with FDCs

Question 14

Where do chemokines choreograph how cells get togehter?

Answer 14

in the lymph node

Question 15

how do DCs, B cell, and T cells know where to go inside a lymph node?

Answer 15

chemoattractive cytokines (chemokines!) produced by FDCs
ex: CXCL13 attracts B cells to interact with FDCs

Question 16

how do B cells know where to get Th help?

Answer 16

• after stimulation by cognate antigen (FDCs), downregulate CXCL13 receptors
• upregulate CCR7 receptors that recognize chemokines produced by cells that direct B cells where to meet up with activate Th cells

Question 17

how do Th cells know where to meet up with B cells

Answer 17

they detect chemokines (CXCR5) so they know where to migrate to the periphery of the paracortex to meet up with B cells

Question 18

follicular helper T cells (Tfh)

Answer 18

when receptors on Th cells (CD28 and ICOS) receive costimulatory signals from the B cell (B7 and ICOSL) to allow Th cell to mature fully into this

Question 19

where T cells proliferate after encountering DC with its cognate antigen

Answer 19

paracortex (After circulating through lymph nodes)

Question 20

what happens after T cells proliferate in the paracortex of a lymph node?

Answer 20

expanded popl’ns leave the lymph node and re-enter other lymph nodes or secondary lymphoid organs via HVs where they may encounter B cells that need their help

Question 21

where does class switching occur or re-stimulation occur for B cells?

Answer 21

secondary lymphoid organs

Question 22

where do B cells set up to produce IgM?

Answer 22

bone marrow or spleen

Question 23

Peyer’s patch in the MALT

Answer 23

• no incoming lymph
• antigens that are able to bind, are taken up by M cells, then delivered to lymphoid follicle within the Peyer’s patch or enter into lymph to go to lymph nodes

Question 24

located between an artery and a vein, this functions as a blood filter

Answer 24

spleen

Question 25

the spleen

Answer 25

• blood filter
• no HEVs
• no incoming or outgoing lymphatics
• blood goes to marginal sinuses where macs clean up debris and resident DCs acquire antigen for pres
• 30 mins to screen blood in our bodies
• B and T cells concentrated in their own area until chemokines call them together

Question 26

purpose of secondary lymphoid organs

Answer 26

• to intercept invaders that enter by different routes

- to provide strategic locations to mobilize appropriate weapons