T cell responses are initated in peripheral lymphoid organs by activated dendritic cells

Question 1

What experiment demonstrated that peripheral lymphoid organs are required to generate a T cell response?

Answer 1

1. Skin flap with arterial supply but no lymphatics was mobilised.
2. Antigen placed in flap
3. No T cell response generated
   Therefore T cells do not become sensitised in the infected tissue itself.

Question 2

Antigens in peripheral tissue are picked up by APCs and transported to PLOs.

1. Where are antigens in the bloodstream transported to?
2. Where are mucosal surface antigens transported to?

Answer 2

1. The spleen

2. Across the mucosa to tonsils or Peyer’s patches.

Question 3

What immune response at the site of infection aids T cell responses?

Answer 3

The innate immune response

Question 4

Name one way the innate immune response aids T cell responses

Answer 4

The innate immune response causes an inflammatory reaction at the site of infection

Question 5

How does an inflammatory reaction at the site of infection aid T cell responses?

Answer 5

Inflammation increases the rate of entry of blood plasma into the infected tissues and thus increases the drainage of ECF to PLOs.

Question 6

List three stimuli that cause immature tissue resident DCs to be activated.

Answer 6

1. Via their TLRs
2. Tissue damage
3. Cytokines produced during the inflammatory response

Question 7

What is the response of a DC to being activated?

Answer 7

The activated DC migrates to regional lymph node and expresses co-stimulatory molecules, in addition to antigen, to activate naive T cells.

Question 8

What other two immune cell types can be induced through antigen nonspecific receptors to express costimulatory molecules and act as APCs? Where are they found?

Answer 8

Macrophages - found in most tissue types including lymphoid tissue
B cells - located primarily in lymphoid tissue

Question 9

Within the lymph node, where are B cells usually located?

Answer 9

In the follicles

Question 10

Within the lymph node, where are macrophages primarily located?

Answer 10

Throughout, but primarily in the marginal sinus and medullary cords

Question 11

Within the lymph node, where are dendritic cells primarily located?

Answer 11

Throughout the cortex, in the T cell areas

Question 12

What are the medullary cords of a lymph node?

Answer 12

Where the efferent lymph collects before passing via efferent lymphatics into the blood

Question 13

What is the marginal sinus of a lymph node?

Answer 13

Where the afferent lymph collects before percolating through the lymphoid tissue

Question 14

What type of APC is the strongest activator of naive T cells?

Answer 14

Mature dendritic cells

Question 15

What is unique about DCs, macrophages, and B cells relative to naive T cells?

Answer 15

Only these three cell types express teh specialised co-stimulatory molecules required to activate naive T cells

Question 16

Under what condition DCs, macrophages, and B cells express co-stimulatory molecules to activate naive T cells?

Answer 16

Only in the context of infection

Question 17

Dendritic cells can take up, process, and present antigens from what type of sources?

Answer 17

All types

Question 18

B cells can take up and present antigens from what type of sources?

Answer 18

They process and present soluble antigens

Question 19

Macrophages can take up and present antigens from what type of sources?

Answer 19

The process and present antigen from ingested pathogens

Question 20

What cell types do B (???and macrophages???) cells mainly interact with?

Answer 20

Already primed effector CD4 T cells