ABSTRACT
Phagocytes are specialized “eating” cells (phagein: Greek, “to eat”), of which there are two main types, neutrophils and macrophages. Neutrophils, often called polymorpho-nuclear cells (PMNs) because of the multilobed nature of their nuclei (Figure 1), are mobile phagocytes that comprise the majority of blood leukocytes (about 8 x 106 per ml of blood). They have a very short half-life (days) and die in the bloodstream by apoptosis A polymorphonuclear cell (neutrophil) in the blood. From Male D, Brostoff J, Roth D & Roitt I (2006) <xref ref-type="bibr" rid="ref6">Immunology</xref>, 7th ed. With permission from Elsevier https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429212857/7842d445-aa7b-4eab-a2db-7351fa123550/content/fig1_B1.jpg" xmlns:xlink="https://www.w3.org/1999/xlink"/> 17(programmed cell death). They have granules that contain peroxidase, alkaline and acid phosphatases, and defensins (Section B2), which are involved in microbial killing. These granulocytes stain with neutral dyes and have a different function from granulocytes that stain with eosin (eosinophils) or basic dyes (basophils). PMNs have receptors for chemotactic factors released from microbes, for example muramyl dipeptide (MDP), and for complement components activated by microbes (Table 1). Their main function is to patrol the body via the bloodstream in search of invading microbes. As such they are pivotal cells in acute inflammation (Section B4). Like the majority of cells involved in the immune system, these phagocytes are produced in the bone marrow (Section A5).
