3️⃣ Leukocyte recruitment

Question 1

What are the five steps of leukocyte recruitment?

Answer 1

1) Margination; 2) Rolling; 3) Adhesion; 4) Transmigration (diapedesis); 5) Chemotaxis.

Question 2

Which adhesion molecules mediate leukocyte rolling?

Answer 2

Selectins: L-selectin (on leukocytes), P- and E-selectin (on endothelium).

Question 3

Which molecules mediate firm leukocyte adhesion?

Answer 3

Integrins (e.g. LFA-1) on leukocytes binding ICAM-1/VCAM-1 on endothelium.

Question 4

What mediates leukocyte transmigration?

Answer 4

PECAM-1 (CD31) at endothelial junctions and leukocyte collagenases.

Question 5

What drives leukocyte chemotaxis?

Answer 5

Chemical gradients of chemokines (e.g. IL-8), bacterial products, complement fragments (C5a), leukotriene B4.

Question 6

How do acute vs chronic inflammation differ in leukocyte types?

Answer 6

Acute: predominately neutrophils; Chronic: predominantly macrophages and lymphocytes.