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© Dirk Biddle
Monocytes circulate in the blood before entering the tissue to mature into macrophages. It can be argued that monocytes represent the circulating macrophage population and should be considered fully functional, but immature macrophages, changing
phenotype in response to factors encountered in specific tissues after migration. The blood monocytes are young cells that already possess migratory,
chemotactic,
pinocytic and phagocytic capacity, as well as receptors for the crystallisable fragment (Fc-domains) of immunoglobulin G (IgG antibody (see section 1.7.10) and inactivated C3b complement.
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Phenotype: The total observable properties or characteristics displayed by an organism under a particular set of environmental factors.
The phenotype of an organism is produced by the interaction of genotype and the environment, regardless of the actual genotype of the organism.
Chemotaxis: Orientation or movement of an organism or cell in relation to chemical agents. (M+)
A response of motile cells or organisms in which the direction of movement is affected by the gradient of a diffusible substance.
Differs from chemokinesis in that the gradient alters probability of motion in one direction only, rather than rate or frequency of random motion. (OMD)
Pinocytosis: The uptake of fluid (and dissolved substance) filled vesicles into cells by invagination and pinching off of the cell membrane (endocytosis - the uptake of material into a cell by the formation of a membrane bound vesicle.). Macro pinocytosis and micro pinocytosis are distinct processes, the latter being energy independent and involving the formation of receptor ligand clusters on the outside of the plasma membrane and clathrin on the cytoplasmic face. (OMD)