Biochemistry of white blood cells

The peculiarities of metabolism in neutrophils

1) they have many lysosomes which contain proteinases such as collagenase, elastase, catepsin G and gelatinase

2) low level of oxidative phosphorylation that due to the lack of mitochondrions and high extent of glycolysis

3) high level of pentose phosphate’s cycle which gives NADPH2 used for formation of AFO

4) there is a specific enzyme myeloperoxidase that catalyzes the next reaction: H2O2 + H⁺ + Cl^- à HOCl (hypochloric acid) + H2O

5) they exrete defensive peptides consisting of 22-30amino acids

6) neutrophils have lysocyme (bactericidial agent)

7) neutrophils output the lactoferrin that is used for profilaxis of cancer and bacteriostatic agent

8) NADPH-oxydase is a specific enzyme that takes part in formation of AFO

9) Neutrophils output selectins and integrins

10) Neutrophils output activator of plasminogen (blood dissolution factor)

The role of neutrophils

They take part in acute inflammation response (AIR). AIR comprizes 3 stages:

1) Chemotaxis and adhesion

2) Respiratory explosion

3) Cleavage of antigenes

1 – chemotaxis is a gathering of neutrophils in inflammatory area. It occurs owing to selectins. Adhesion is a sticking of neutrophils to the vessels in inflammatory area due to the integrins

2 – respiratory explosion is an activation of all metabolic processes in neutrophils causing the distructruction of invaded antigenes. It accomplishes by migration of phagocytes from vessel and intensive formation of AFO

3 – cleavage of antigenes occurs due to proteinases of lysosomes

The concept of respiratory explosion

This phenomenon is characteristically for all phagocytes including neutrophils. Neutrophils are activated through specific reseptors which joined with G-protein and phospholipase C. the activation of Phospholipase C results in cleavage of phosphoinositoldiphosphate to inositoltriphosphate and DAG. ITP promotes releasing of calcium from endoplasmic reticulum. DAG activates protein kinase C that phosphorylates NADPH-oxydase. Beside of this the intake of calcium into cells from extracellular matrix occurs owing to G-Protein. Increase of calcium in cytosol of cells causes the assembleying of microtubules and actomyosin in neutrophils that results in migration of neutrophils to inflammatory area. The phosphorylation of NADPH-oxydase results in formation of AFO (see below). This accomplishes by intensive uptake of oxygen.