Mononuclear Phagocytes: The Monocyte Macrophage System

Nearly all tissues, organs, and serosal cavities harbor a population of resident phagocytes. Most contain only a diffuse scattering of individual phagocytic cells that remain inconspicuous under normal conditions and are very similar to one another in appearance and function. In some tissues, however, phagocytes are especially abundant or have distinctive morphologic features and are known by specific names. Examples include the Kupffer cells that line sinusoids of the liver (and account for nearly 10% of total liver mass), osteoclasts in bone, or microglial cells of the brain (Table bellow). (more…)

Leukocyte Chemotactic Factors

Once it is tethered onto the venule wall, the neutrophil or other leukocyte comes into contact with a wide variety of inflammatory mediators that may either be expressed by the activated endothelium or simply diffuse into the blood from the injured tissue. Among these mediators are a diverse subset of intermediaries known as leukocyte chemotactic factors which bind to receptors on the leukocyte surface and trigger the second, activation phase of margination. (more…)