Editing Chemotaxis (section)

===Detection of a gradient of chemoattractant===
The specific molecule/s that allow a eukaryotic cells detect a gradient of chemoattractant ligands (that is, a sort of the molecular compass that detects the direction of a chemoattractant) seems to change depending on the cell and chemoattractant receptor involved or even the concentration of the chemoattractant. However, these molecules apparently are activated independently of the motility of the cell. That is, even an immnobilized cell is still able to detect the direction of a chemoattractant.<ref>{{cite journal | vauthors = Rodríguez-Fernández JL, Criado-García O | title = A meta-analysis indicates that the regulation of cell motility is a non-intrinsic function of chemoattractant receptors that is governed independently of directional sensing | journal = Front. Immunol. | volume = 13 | issue = eCollection 2022 | pages = 10011086 | date = October 2022 | pmid = 36341452}}</ref> There appear to be mechanisms by which an external chemotactic gradient is sensed and turned into an intracellular Ras and [[PIP3]] gradients, which results in a gradient and the activation of a signaling pathway, culminating in the [[polymerisation]] of [[actin]] filaments. The growing distal end of actin filaments develops connections with the internal surface of the plasma membrane via different sets of peptides and results in the formation of anterior [[pseudopods]] and posterior [[Uropod (immunology)|uropods]].<ref>{{cite journal | vauthors = Pal DS, Banerjee T, Lin Y, de Trogoff F, Borleis J, Iglesias PA, Devreotes PN | title = Actuation of single downstream nodes in growth factor network steers immune cell migration | journal = Developmental Cell | volume = 58 | issue = 13 | pages = 1170–1188.e7 | date = July 2023 | pmid = 37220748 | pmc = 10524337 | doi = 10.1016/j.devcel.2023.04.019 }}</ref><ref>{{cite journal | vauthors = Lin Y, Pal DS, Banerjee P, Banerjee T, Qin G, Deng Y, Borleis J, Iglesias PA, Devreotes PN | title = Ras suppression potentiates rear actomyosin contractility-driven cell polarization and migration | journal = Nature Cell Biology | pages = 1–15 | date = July 2024 | pmid = 38951708 | doi = 10.1038/s41556-024-01453-4 | pmc = 11364469 }}</ref>
[[Cilium|Cilia]] of eukaryotic cells can also produce chemotaxis; in this case, it is mainly a Ca<sup>2+</sup>-dependent induction of the [[microtubule|microtubular]] system of the [[basal body]] and the beat of the 9&nbsp;+&nbsp;2 microtubules within cilia. The orchestrated beating of hundreds of cilia is synchronized by a submembranous system built between basal bodies.
The details of the signaling pathways are still not totally clear.

====Chemotaxis-related migratory responses====
[[Image:Chtxphenomen1.png|right|400 px|<div style="text-align: center;border:none">Chemotaxis related migratory responses</div>]]
Chemotaxis refers to the directional migration of cells in response to chemical gradients; several variations of chemical-induced migration exist as listed below. 
* ''[[Chemokinesis]]'' refers to an increase in cellular motility in response to chemicals in the surrounding environment. Unlike chemotaxis, the migration stimulated by chemokinesis lacks directionality, and instead increases environmental scanning behaviors.<ref>{{cite journal | vauthors = Becker EL | title = Stimulated neutrophil locomotion: chemokinesis and chemotaxis | journal = Archives of Pathology & Laboratory Medicine | volume = 101 | issue = 10 | pages = 509–13 | date = October 1977 | pmid = 199132 }}</ref> 
* In ''[[haptotaxis]]'' the [[gradient]] of the chemoattractant is expressed or bound on a surface, in contrast to the classical model of chemotaxis, in which the gradient develops in a soluble fluid.<ref name="pmid6030602">{{cite journal | vauthors = Carter SB | s2cid = 4212997 | title = Haptotaxis and the mechanism of cell motility | journal = Nature | volume = 213 | issue = 5073 | pages = 256–60 | date = January 1967 | pmid = 6030602 | doi = 10.1038/213256a0 | bibcode = 1967Natur.213..256C }}</ref> The most common biologically active haptotactic surface is the [[extracellular matrix]] (ECM); the presence of bound [[ligands]] is responsible for induction of transendothelial migration and [[angiogenesis]].
* ''[[Necrotaxis]]'' embodies a special type of chemotaxis when the chemoattractant molecules are released from [[necrosis|necrotic]] or [[apoptosis|apoptotic]] cells. Depending on the chemical character of released substances, necrotaxis can accumulate or repel cells, which underlines the pathophysiological significance of this phenomenon.