Cell Movement Flashcards
What are the three reasons leukocytes migrate?
- To fight infections
- Patrol tissues
- Deliver immune responses to specific sites
Where do myeloid cells migrate from and to?
From blood into tissues
Where do lymphocytes migrate from and to?
- Primary lymphoid organs to secondary lymphoid organs
- Secondary lymphoid organs to sites of infection
What are the three factors that help immune cells find their destination?
- Infected tissue
- Chemokines
- Adhesion molecules
What is homing?
The migration of leukocytes to specific sites
What is recruitment or migration?
Movement of leukocyte from blood into tissues especially at sites of inflammation
What is recirculation?
Continuous movement of lymphocytes from blood to lymphoid tissue back to blood
What are the two main classes of adhesion molecules?
- Selectins and selecting ligands
- Intergrins and integrin ligands
Do all leukocytes express the same adhesion molecules?
No
What do selectins bind?
Carbohydrate structures
Where are selectins expressed?
On the plasma membrane of endothelial cells and leukocytes
What do selectins mediate?
The initial low affinity step of leukocyte rolling on the endothelium
What induces selectin expression?
Cytokines like TNF and IL-1
What is the structure of integrins?
Alpha and beta chains
What do integrins do?
Integrate signals from extracellular ligands into cytoskeletal changes
What happens to integrin affinity when activated?
It increases upon receiving intracellular signals
How do cells follow chemokines?
By moving up the chemokine gradient
What are two example of selectin?
E-selectin and P-selectin
What stimulates endothelial cells to express E-selectin and P-selectin?
TNF and IL-1
What do circulating phagocytes express to bind selectins?
Surface carbohydraes
What does the weak binding between selectin and surface carbohydrates?
Leukocytes roll along the vessel wall
What adhesion molecules are expressed by leukocytes during firm adhesion?
Integrins
What produces chemokines at infection sites?
Tissue resident cells
What is the function of chemokines produced by tissue resident cells?
- Increase integrin affinity
- Direct leukocyte migration
