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Under haptotaxis (of gr. Haptein "touch", "attach" and taxis "order", "staging") is in biology and medicine , the movement of cells understood and cell processes, which at a concentration gradient of a structure-bound signaling substance based (Haptotaxin). In contrast to haptotaxis, in chemotaxis the concentration gradient (the chemotactic gradient) of a dissolved signal substance (chemotaxin) determines the direction of movement. In complex living beings ( metazoa) the signal stimulus usually causes cell migration in the direction of the higher concentration of the signal substance (positive haptotaxis or chemotaxis), but the opposite is also possible (negative haptotaxis or chemotaxis).

Chemotaxis and haptotaxis are essential organizational elements in the design movements during embryonic development , but also later in growth, remodeling and healing processes, e.g. B. in the outgrowth of nerve cell processes (axogenesis) or of vessels (angiogenesis). Cells of the immune system or bacteria (e.g. Escherichia choli ) also orientate themselves on the basis of such stimuli.

Haptotactic signals can originate from specific structures of the cell surface as well as the intercellular substance (e.g. connective tissue fibers). An example of a molecule that exerts a haptotactic stimulus on neutrophil granulocytes in the bloodstream is the receptor PECAM 1 (CD31), which is increasingly expressed on endothelial cells of the inflammation site in the event of inflammation . Its increasing density towards the cell periphery leads an adhesive granulocyte to the cell edge, where it can leave the bloodstream at the point of contact with the neighboring cell (diapedesis).

See also