Immune Cell Trafficking

Question 1

What do cells travel in?

Answer 1

Blood and lymph

Question 2

Immune cells travelling in the blood

Answer 2

• Arteries
• High endothelial venules
• Venes

Question 3

Immune cells travelling in the lymph

Answer 3

• Extracellular fluid
• Collected in the lymphatics, drains into the lymph nodes which filter for free antigens and antigen presentation occurs.
• They will eventually flow out and make it to the ductus thoracicus flowing into the blood where immune cells can then reach tissues
• Passive flow, no valves or strong wall

Question 4

Immune cells moving in the blood

Answer 4

• All immune cells travel in the blood
• Granulocytes, phagocytes, RBCs and thrombocytes, lymphocytes
  o Naïve T and B cells migrate into secondary lymphoid tissues
  o Effector and memory T cells migrate to site of infection

Question 5

General Movement Cycle of T cells

Answer 5

1. Start life in thymus
2. Move in high endothelial venules to the lymph nodes
3. After some time, naïve T cells will move out of one lymph node through the efferent vessels and re-enter the blood through the thoracic duct to get to other lymph nodes
4. When in a lymph node, T-cells are activated by antigen presenting cells
5. T-cells go through proliferation and differentiation stage in the lymph nodes
6. Exit lymph node via efferent lymphatics and enter circulation in high numbers
7. Travel in high endothelial venules and reach peripheral tissues. Enter the site of infection and execute effector functions

Question 6

Leaving the High endothelial venules (HEVs) to get to destination tissues

Answer 6

• Facilitate extravasation of lymphocytes into lymph nodes
• Inner layer is endothelial cells which release many different types of molecules that tell immune cells where they are and what they need to do (help them find the correct tissues/location and migrate into the secondary lymphoid tissues)

Question 7

Stages of leukocyte trafficking

Answer 7

Mediated by a combination of receptor-ligand interactions (adhesion molecules)

1. Rolling (selectins)
2. Activation (chemokines)
3. Adhesion (integrins)
4. Diapedesis (chemokines)

Question 8

Adhesion molecules

Answer 8

• Help cells to migrate and communicate with each other
• Comprised of different families; different types of proteins

Question 9

Chemokines

Answer 9

• Family of small soluble proteins
• Secreted

Function: chemoattractants for immune cells

Examples: interleukin 8, lymphotactin

Question 10

Types of Adhesion molecules

Answer 10

• Chemokines
• Selectins
• Integrins

Question 11

Selectins

Answer 11

• Expressed on the cell surface
• Allow immune cells to extravasate
• Allow for tighter binding for cells to bind and move through

Question 12

Integrins

Answer 12

• Expressed on cell surface
• Allow immune cells to migrate to specific tissues
• Allow for tighter binding for cells to bind and move through

Question 13

Monocyte Chemoattractant Protein-1 (MCP-1)

Answer 13

• An example of a chemokine
• Regulates migration and infiltration of monocytes/macrophages

Question 14

Homing of cells

Answer 14

• Very specific process
• Different combinations of molecules are expressed on endothelial cells of tissues and they bind with specific molecules on immune cells