Chapter 7 AI generated

Question 1

Describe the role of FDCs in the immune system.

Answer 1

FDCs can activate B cells by binding to antibodies, leading to the formation of germinal centers where B cells proliferate.

Question 2

What is the function of high endothelial venules (HEVs) in secondary lymphoid organs?

Answer 2

HEVs serve as entry points for B and T cells from the blood into organs like lymph nodes.

Question 3

How do lymphocytes enter a lymph node and what is their exit route?

Answer 3

Lymphocytes can enter a lymph node via lymphatics or blood vessels, but they can only exit through lymphatics.

Question 4

Define germinal center in the context of the immune system.

Answer 4

Germinal centers are regions within lymphoid follicles where B cells proliferate and undergo processes like somatic hypermutation and class switching.

Question 5

What is the role of Th cells in supporting B cell survival in germinal centers?

Answer 5

Th cells provide co-stimulation signals to proliferating B cells, helping them escape apoptosis and continue their development.

Question 6

How do chemokines regulate the distribution of B and T cells within lymph nodes?

Answer 6

Chemokines like CXCL13 produced by FDCs attract naive B cells to the cortex, while other chemokines help in the accumulation of T cells in the paracortex.

Question 7

Describe the role of Tfh cells in the immune system.

Answer 7

Tfh cells help rescue germinal B cell centers and facilitate class switching.

Question 8

What happens when a T cell cannot find the appropriate DC in a lymph node?

Answer 8

It moves on to another DC until it finds the right one.

Question 9

Define the process of recirculation in the immune system.

Answer 9

It involves T cells leaving lymph nodes, circulating through blood, and re-entering lymph nodes via HEVs.

Question 10

How do CTLs kill infected cells in the immune response?

Answer 10

They exit the blood at the site of infection to kill the target cells.

Question 11

Describe the two major reasons for the swelling of lymph nodes during an immune response.

Answer 11

Proliferation of lymphocytes in the node and cytokines produced by Th cells recruiting macrophages.

Question 12

What are Peyer’s patches and what role do they play in the immune system?

Answer 12

They are mucosal-associated lymphoid tissue in the small intestine that help in immune surveillance and response.

Question 13

How do antigens enter Peyer’s patches if they lack incoming lymphatics?

Answer 13

Antigens enter through M cells that sample luminal contents and transport antigens across the epithelium.

Question 14

Explain the role of M cells in the immune system.

Answer 14

M cells sample luminal antigens, transport them across the epithelium, and play a crucial role in antigen uptake in Peyer’s patches.

Question 15

What is the significance of endosomes in the immune response?

Answer 15

Endosomes are vesicles that carry antigens collected by M cells and transport them through the cell for immune processing.

Question 16

Describe the function of the spleen the immune system.

Answer 16

The spleen functions as a blood filter, where about 5% of the blood passes through with each pump of the heart, taking approximately half an hour to filter all the blood. It lacks lymphatics and high endothelial venules (HEVs), allowing all blood to enter without selection.

Question 17

Explain the role of marginal sinuses in the spleen.

Answer 17

Marginal sinuses in the spleen are lined with macrophages that clean the blood. Naive B and T cells travel along with the blood but stick to specific regions: T cells gather in the periarteriolar lymphocyte sheath (PALS), while B cells reside between PALS and marginal sinuses.

Question 18

How do antigen-presenting cells (APCs) function in the spleen?

Answer 18

APCs in the spleen, originating from the marginal sinuses, take up antigens from invaders in the blood and present them using MHC II. Activated DCs travel to the PALS where T cells gather, serving as ‘travelers’ within the spleen.

Question 19

Define lymphocyte trafficking in the immune system.

Answer 19

Lymphocyte trafficking involves around 500 billion lymphocytes circulating through the body daily in a well-defined traffic pattern. Virgin and experienced lymphocytes follow different routes, with T cells passing through bone marrow, thymus, and secondary lymphoid organs (SLOs) guided by adhesion molecules.

Question 20

How do experienced T cells differ from naive T cells in terms of trafficking?

Answer 20

Experienced T cells, upon activation in SLOs, acquire specific adhesion molecules that allow them to return to the activation site for re-stimulation. They also gain molecules that guide them to exit the blood at the appropriate location, similar to neutrophils leaving the blood.

Question 21

Describe the trafficking pattern of B cells in the immune system.

Answer 21

B cells follow a similar trafficking pattern to T cells, but experienced B cells tend to settle in SLOs or bone marrow rather than circulating extensively. Most of them remain in these locations to produce antibodies.