Contactmediated

Contactmediated, often written as contact-mediated signaling or juxtacrine signaling, refers to biological processes that require direct physical contact between cells or between a cell and its surrounding extracellular matrix. In these mechanisms, information is transmitted through membrane-bound ligands and receptors or through stable cell–cell junctions, rather than through diffusible soluble factors.

Key concepts include juxtacrine signaling, wherein membrane-bound ligands on one cell engage receptors on an adjacent cell (as with Notch signaling), and contact-dependent adhesion that influences cell fate, migration, and tissue organization. Eph-ephrin signaling is another example of contact-dependent communication, which can guide boundary formation and tissue patterning. Adhesion molecules such as cadherins and integrins enable and stabilize these encounters.

In immunology, contact-mediated cytotoxicity (CMC) describes the killing of a target cell by cytotoxic T cells or natural killer cells through a stable immunological synapse, requiring physical contact. Similar mechanisms contribute to immune surveillance, development, and tissue homeostasis, while disrupting contact cues can lead to developmental defects or disease, including cancer progression via altered cell adhesion.

Experimental approaches to study contact-mediated processes distinguish between contact-dependent and soluble signaling, using co-culture systems, Transwell setups, live-cell imaging, and molecular perturbations of specific ligands or receptors.

See also juxtacrine signaling, contact inhibition, immunological synapse, Notch signaling.