Inflammation-Exudation and Leukocyte Migration

Question 1

What are the types of exudate?

Answer 1

–Serous: watery, clear or cloudy, low protein, low cell exudate observed in mild reaction of serous or synovial membranes

–Fibrinous: abundant, rich in fibrinogen, more severe reactions involving serous membranes, alveoli, and CT, serous component may be in pockets as clear yellow watery exudate

–Catarrhal: abundant or more restricted, cloudy thin mucinous or sticky white, inflammation of mucous membranes of nasopharynx, airways, lower alimentary, uterus or mucous glands, rich in desquamated epithelial cells and neutrophils

–Suppurative/purulent: associated with bacterial infection by pyogenic organisms, large amounts of pus (large # of dead or dying neutrophils and necrotic tissue debris partly liquefied), smelly, accumulates in abscess or cellulitis (diffuse spread along fascial planes)

–Hemorrhagic: may occur during development of inflammatory reaction, organs rich in vascular supply

–Necrotising: can be result of ischemia or thrombosis

Question 2

What are the stages of leukocyte migration?

Answer 2

Two main stages: margination and emigration

Sub-stages:

• Tethering and rolling: expression of selectins by endothelium to tether passing leukocytes
• Chemoattractants activate tethered leukocyte which expresses integrin
• leukocyte binds cell adhesion molecules of immunoglobulin superfamily to cause final arrest
• Migration through gaps of endothelial cells, traverse into tissues

*Neutrophils first to do this process, later monocytes (become active phagocytic macrophages)

Question 3

What are the two pathways of neutrophil arrest in the circulation near inflammatory sites?

Answer 3

–Immediate: mins after, rapid expression of P selectin by endothelial cells, binds to neutrophil P selectin receptor (mediated by histamine, PAF, and C5a) causing tethering and rolling; C5a (chemoattractant) causes neutrophil activation and expression of LFA-1 which binds ICAM-1 on endothelium

–Delayed: 2-4 hours after, expression of E selectin on endothelial cells brought on by action of IL-1 and TNF-alpha (cytokines) on endothelial cells; E selectin bind receptors on neutrophils and activates tethering and rolling; chemoattractants (LTB4, IL-8) cause neutrophil expression of LFA-1 binding ICAM-1 to cause arrest, then migration into tissue

Question 4

What are the steps of monocyte adhesion?

Answer 4

• Monocytes express receptors for selectins that mediate tethering and rolling
• Activation due to monocyte chemotactic factor (MCP-1) which is synth’d and secreted by macrophages at site of damage
• LFA-1 binds ICAM-1 on endothelium to cause arrest and initiate migration
• slower than neutrophils due to slow production of MCP-1

Question 5

What are some of the chemotactic factors for neutrophils?

Answer 5

C3a, C5a, PGE1/2, LTB4, IL-8, bacterial products

neutrophils will follow the chemotactic gradient

Question 6

What are the roles of macrophages in acute inflammation and host defense?

Answer 6

• -phagocytose pathogens opsonized by antibodies and complement
• -secrete toxic factors to kill pathogen
• -secrete cytokines and chemokines to attract other immune cells
• -secrete colony stimulating factors to promote differentiation of recruited immature granulocytes and monocytes