Chapter 3 Leukocyte Circulation and Migration into Tissues pgs 37-43 Flashcards Preview

Medical Immunology Bios 443/843 > Chapter 3 Leukocyte Circulation and Migration into Tissues pgs 37-43 > Flashcards

Flashcards in Chapter 3 Leukocyte Circulation and Migration into Tissues pgs 37-43 Deck (18):

Why does the immune system move its cellular components into the tissues? What structures? (3)

1) Delivery of leukocytes
2) Delivery of lymphocytes
3)Delivery of effector lymphocytes


Adhesion of circulating leukocytes to vascular endothelial cells is mediated by two classes of molecules. What are those two classes of molecules called?

Selectins and integrins.



plasma membrane carbohydrate-binding adhesion molecules that mediate an initial step of low-affinity adhesion of circulating leukocytes to endothelial cells lining post-capillary venules. (expressed on leukocytes and endothelial)


E- selectin

(CD62E) Expressed on the endothelial cell surface within 1 to 2 hours in response to the cytokines interleukin-1 (IL-1) and tumor necrosis factor (TNF) TNF and IL-1 produced by tissue macrophages in response to infection.


Sialylated Lewis X

Ligands on leukocytes that bind to E-selectin and P-selectin on endothelial cells.



(CD62L) expressed on leukocytes and not on endothelial cells. ligands are sialomucins on endothelial cells.



cell surface proteins that mediate adhesion of cells to other cells or to extracellular matrix, through specific binding interaction with various ligands.



(Leukocyte function associated antigen 1) integrin associated with leukocytes responsible for adhesion to endothelial cells, lymphocytes, dendritic cells, macrophages, fibroblasts, and keratinocytes.



ligand for LFA-1. Intracellular adhesion molecule-1 a membrane glycoprotein expressed on cytokine-activated endothelial cells, lymphocytes, dendritic cells, macrophages, fibroblasts, and keratinocytes.


Integrin activation

the process by which integrins respond to intracellular signals by rapidly increasing their affinity for ligands. Occurs in all leukocytes in response to chemokine binding to chemokine receptor, and in T cells when antigen binds to antigen receptors. Leads to increased affinity for receptors on endothelial cells.



Extreme eagerness or enthusiasm. The overall strength of binding between an antigen and an antibody.


Leukocyte recruitment from blood into tissues is regulated by the action of what molecule?

Chemokines specifically CXCL8


What are the two roles that cytokines play in inflammation?

1) Increased adhesion of leukocytes to endothelium (signals from chemokine receptors lead to increased integrin affinity)
2) Migration of leukocytes to site of infection or tissue damage. (Via Chemokinesis)



Chemokine Receptors: CXCR1, CXCR2; Major function, Neutrophil recruitment


What sequence of events leads to leukocytes migrating into tissues?

1) Selectin-mediated rolling of leukocytes on endothellium (rolling occurs due to low affinity Kd of ligand to selectin receptors. They continually bind, roll, and bind);
2) Chemokine-mediated increase in affinity of integrins:(Chemokines displayed on endothelial surfaces increase affinity of leukocytes)
3) Stable integrin-mediated adhesion of leukocytes to endothelium: ICAM-1 binds to LFA-1 causing firm attachement to the endothelium.;
4) Transmigration of leukocytes through the endothelium



The process by which leukocytes flow toward the lining of of vessels. This occurs, because leukocytes are much larger than rbcs, so they move away toward the central axis of flow.


Paracellular Transmigration

The process by which leukocytes transmigrate between the borders of endothelial cells to reach extravascular tissues.


What leukocytes are recruited to sites of infection and injury? How are they recruited there?

1) Neutrophils and monocytes are recruited to tissue sites of infection and injury; 2) they are recruited via a selectin, integrin, and chemokine-dependent multistep process

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