The importance of "infectious defense" lies in defense against extracellular bacteria. Neutrophils are able to perform effector functions immediately, without signals from other cells.
They make up '60-70% 'of peripheral blood leukocytes. They occur in the bloodstream for 6-12 hours and in the tissue for 4-5 days. Only 7% of the total number is found in the peripheral blood, 93% is found in bone marrow (it changes under the influence of inflammatory cytokines and bacterial products). The main chemotactic substance is chemokine IL-8.
The main function of neutrophils is phagocytosis. Their "azurophilic" granules contain many lytic enzymes. When killing microbes, they can, with a sufficient supply of energy, cause the so-called oxidative flare. At the same time, they secrete substances that lead to the development of inflammatory responses.
Neutrophils cannot divide or supplement their granular equipment. Activated neutrophils die after performing their functions and become part of the inflammatory deposit. Dead neutrophils form 'pus' .
Neutrophils 'do not belong' to APCs!
Development line: Myelodid progenitor cell bone marrow → myeloid precursor → 'neutrophil' .
A progenitor cell, not just neutrophils, has an adhesive molecule CD34. It is found in small numbers in the marrow for life.
Their 'nucleus' is made up of 2–5 lobes, the number of lobes increases with the age of the cell (the youngest forms of neutrophils do not have a segmented nucleus and are therefore referred to as rods). There are tiny, light pink granules in the cytoplasm of neutrophils. Their main role is phagocytosis. 
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