Inflammatory cells

PMN – polymorphonuclear granulocyte
· White blood cells with nuclei of varied forms, characterized by the presence of granules in their cytoplasm
· Granulocytes or PMN are released from the bone marrow by the regulatory complement proteins.

Neutrophils
· A PMN granular leukocyte
· They are the circulating white blood cells essential for phagocytosis and proteolysis
· Neutrophils are normally found in the bloodstream and are the most abundant type of phagocyte, constituting 50% to 60% of the total circulating white blood cells.
· Live approximately five days
· Once neutrophils have received the appropriate signals, it takes them about thirty minutes to leave the blood and reach the site of an infection
· Rapidly engulf invaders coated with antibodies and complement, and damaged cells or cellular debris.
Neutrophils do not return to the blood; they turn into pus cells and die

Eosinophilic granulocytes
· They are antigen presenting cells, they regulate other immune cell functions

· Kill parasites (e.g. enteric nematodes) because their granules contain a unique, toxic basic protein and cationic protein receptors that bind to IgE
· These cells also have a limited ability to participate in phagocytosis
· Involved in the destruction of tumor cells
· Promote the repair of damaged tissue
· A chemical called interleukin - 5 interacts with eosinophils and causes them to grow and differentiate

Basophilic granulocytes, mast cells
Basophils are one of the least abundant cells in bone marrow & blood

When an infection occurs mature basophils will be released from the bone marrow and travel to the site of infection
When basophils are injured they will release histamine; this contributes to the inflamm response that helps fight invading organisms.

Histamine causes dilation and increased permeability of capillaries close to the basophil.
Injured basophils and other leukocytes will release another substance called prostoglandins that contributes to an increased blood flow to the site of infection. Both of these mechanisms allow blood clotting elements to be delivered to the infected area (this begins the recovery process and blocks the travel of microbes to other parts of the body)
Increased permeability of the blood also allows for more phagocyte migration to the site of infection so that they can consume microbes

Thrombocytes

In mammals thrombocytes = Platelets, key role in blood clotting

Platelets - are small, irregularly-shaped anuclear cell fragments

Average lifespan of a platelet is normally just 5 to 9 days

Platelets play a fundamental role in hemostasis and are a natural source of growth factors

If the number of platelets is too low, excessive bleeding can occur

If the number of platelets is too high, blood clots can form = thrombosis

Platelets release a multitude of growth factors including platelet-derived growth factor (PDGF), & TGF beta, which stimulates the deposition of extracellular matrix.

Both of these growth factors have been shown to play a significant role in the repair and regeneration of connective tissue.