- In tissue

- Contain granules which are mediators of inflammation

- Key players in initiation of inflammation

- Cause vasodilation and chemotaxis

- Histamine

-Heparin

- Serotonin

-recruit WBC's to the site and activate many of the recruited cells to produce their own mediators of inflammation

- Dilates post capillary venules

- Leads to:

Edema

Warmth

Redness

Attraction of inflammatory cells to the site (chemotaxis)

-Circulate in blood in inactive ofrm

- Are activated by endothelial injury

- Maintain the integrity of endothelium

- Essential for coagulation

- Release growth factors (healing) and chemotaxis

- Line vessels and keep cells and plasma inside

- When disrupted, the underlying collagen is exposed, which initiates inflammation

- Damaged endothelial cells secrete prostaglandins (vasodilation) and adhesion molecules (extravasation)

- Recognize certain antigens on surface of bacteria and foreign cells w/o prior activation or exposure

- Kill infected cells by use of perforin and granzymes to lyse target cell or by causing the cell to self destruct by apoptosis

Neutrophil, Eosinophil and Basophil

- all play a role in mediating inflammatory activity

- most numerous granulocyte

- important role in acute inflammation, phagocytosis and chemotaxis

- multi-lobed nucleus

- associated with allergic diseases and with parasitic infections

- accumulate in the affected tissue and contribute to the chronic inflammatory reaction

- least common granulocyte

- contain large cytoplasmic granules

- similar characteristics of a mast cell

Leukocyte extravasation steps

(4)

(1) Chemoattration- leukocytes are localized toward the site of injury due to chemoines

(2) Rolling adhesion- leukocytes bind to the inner wall of the vessel causing them to slow down and roll along the endothelial lining

(3) Tight adhesion- leukocytes bind to receptors on endothelial cells

(4) Transmigration- (diapedesis) leukocytes pass through the gaps between endothelial cells then migrate along a chemotatic gradient toward the site of injury

any molecule that acts as a binding enhancer for the process of phagocytosis

examples/

IgG and C3b

- Active form in tissue

-Activated by IFN that is secreted by lymphocytes

- Professional phagocytes

- Better equipped to handle hard to kill intracellular bacteria

- Have lysosomal enzymes or digestive enzymes that destroy worn out organelles or foreign pathogens

- Macrophages, Dendritic cells and to a limited extent B cells

- They phagocytize the foreign particle into small pieces (antigen) and present it to a helper T cell

- Plays a critical role in wound healing

- Produce 2 substances that make up extracellular matrix to heal a wound:

1) ground substance (glycosaminoglycans)

2) fibers (reticular, collagen, and elastin)

- Contribute most at the end of inflammation during wound healing

- Small cells

- In blood they make up 25% of leukocytes

- "Brain fo the inflammatory reaction"

- Process antigens, secrete antibodies, activate cells, secrete cytokines, recruit leukocytes from blood, induce fever, kill infected cells

-Types: T cells, B cells, Natural Killer cells

 -Express CD4 surface protein

- Activated by APC's

- Activate B cells, cytotoxic T cells and phagocytic cells

- Communicates w/ lymphokines

- Few remain as memory cells

-Express CD8 surface protein

- Recognizes a specific antigen

- Activated by helper T cells

- Secrete perforin and granzymes to kill infected cells

- Undergo clonal proliferation when activated by CD4 helper T cells