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The significance of chemotaxis in biology and clinical pathology was widely accepted in the 1930s, and the most fundamental definitions underlying the phenomenon were drafted by this time. [by whom?] The most important aspects in quality control of chemotaxis assays were described by H. Harris in the 1950s. [12]
Other chemotaxis assay techniques Besides the above-mentioned two most commonly used family of techniques, a wide range of protocols were developed to measure chemotactic activity. Some of them are only qualitative, like aggregation tests, where small pieces of agar or filters are placed onto a slide and accumulation of cells around is measured.
Thus, by using the natural process of chemotaxis, researchers aim to guide these tiny droplets by using chemical gradients released by a specific cell, tissue, or organ within the body. [2] [4] [12] In fact, a few examples of microdroplet systems that use chemotaxis are self-propelling, ionic liquid-based, and synthetic base.
Chemotaxis is a response elicited by chemicals: that is, a response to a chemical concentration gradient. [8] [7] [13] For example, chemotaxis in response to a sugar gradient has been observed in motile bacteria such as E. coli. [14]
For example, there are four well-characterised MCPs found in Escherichia coli: Tar (taxis towards aspartate and maltose, away from nickel and cobalt), Tsr (taxis towards serine, away from leucine, indole and weak acids), Trg (taxis towards galactose and ribose) and Tap (taxis towards dipeptides).
These cellular movements can be directed by external stimuli, a phenomenon known as taxis. Examples include chemotaxis (movement along chemical gradients) and phototaxis (movement in response to light). Motility also includes physiological processes like gastrointestinal movements and peristalsis.
Recent results proved that chemokines (e.g. IL-8, RANTES) are working on long-term chemotaxis receptors, while vasoactive peptides (e.g. endothelin) act more on the short-term ones. Term chemotactic selection is also used to design a technique which separates eukaryotic or prokaryotic cells upon their chemotactic responsiveness to selector ligands.
For example, the Slit protein that mediates axonal chemorepulsion has also been shown to inhibit the directed migration of leukocytes in response to chemoattractants. [5] Other factors might also provide chemorepulsive effects on immune cells, and these inhibitory effects might be regulated by the tissue microenvironment.