Cell biology

Immortalised cell line

Immortalised cell line (continuous cell line): cells engineered or mutated to divide indefinitely, first achieved with HeLa in 1951; made via telomerase (TERT), SV40, or HPV oncoproteins; authenticated by STR profiling; ICLAC lists 486 misidentified lines.

Immunocytochemistry

Immunocytochemistry (ICC), often called immunofluorescence when the label is a fluorophore, is a microscopy method using antibodies to detect and localize proteins within fixed cultured cells.

Immunoelectron microscopy

Immunoelectron microscopy (IEM) combines antibody-based labeling with electron microscopy to localize specific antigens at ultrastructural resolution in cells and tissues, typically using colloidal gold particles as electron-dense probes.

Immunofluorescence staining

Immunofluorescence staining is a microscopy method that uses fluorescently labeled antibodies to detect and localize specific antigens in cells or tissue sections, first demonstrated by Coons and colleagues in 1942.

Immunogold labeling

Immunogold labeling is an electron microscopy technique that uses antibodies attached to colloidal gold particles to detect and localize specific antigens in cells, tissues, and viral particles.

Immunomagnetic separation

Immunomagnetic separation (IMS) is a bench technique that uses antibody-coated magnetic beads to capture target cells, bacteria, or vesicles, underlying commercial platforms such as Dynabeads and MACS.

Impedance cytometry

Impedance cytometry is a label-free flow cytometry technique that measures the electrical impedance of individual cells passing through a microfluidic aperture, quantifying cell size and dielectric properties without stains or optics.

IMR-32

IMR-32 (ATCC CCL-127, CVCL_0346) is a continuous human neuroblastoma cell line established in 1967 from a 13-month-old boy, hyperdiploid, MYCN-amplified with 1p deletion, and a standard model of high-risk neuroblastoma.

IMR-90

IMR-90 (Institute for Medical Research-90), ATCC CCL-186, is a finite human fetal lung diploid fibroblast cell line derived in 1975 from a 16-week female fetus for the NIA Aging Cell Repository, a standard model for cellular aging and senescence.

In vitro

In vitro, Latin for "in glass," describes experiments performed outside a living organism, usually on cells, tissues, or biomolecules, and contrasts with in vivo and in silico methods.

In vivo

In vivo (Latin, "within the living") means experiments performed inside a living organism, contrasted with in vitro and ex vivo; central to preclinical drug validation, regulated by 3R animal-welfare principles, and limited by cost, ethics, and species differences.

Inclusion bodies

Inclusion bodies are circumscribed deposits of foreign or metabolically inactive material in the cytoplasm or nucleus, spanning glycogen and lipid stores, viral replication compartments such as Negri bodies, and amyloid-like bacterial protein aggregates.

Indirect immunofluorescence

Indirect immunofluorescence is a microscopy detection method in which an unlabeled primary antibody binds an antigen and a fluorophore-tagged secondary antibody makes the binding visible, amplifying the signal.

Inscuteable

Inscuteable (Insc; insc, CG11312) is a Drosophila adaptor protein of asymmetric cell division: it links Par polarity complexes to Pins/LGN, orients spindles apico-basally, and competes with NuMA for LGN binding; human INSC mutations cause CMT2 neuropathy.

Integrin

Integrins: heterodimeric αβ cell adhesion receptors linking extracellular matrix to the cytoskeleton, with bidirectional signaling via talin and kindlin; targets of drugs such as vedolizumab for IBD.

Integrin signaling

Integrin signaling: bidirectional signal transduction by 24 αβ heterodimeric adhesion receptors (18 α, 8 β subunits) linking ECM to actin; talin/kindlin/RAP1 drive inside-out activation, FAK and focal adhesions outside-in; basis of antithrombotic, immunologic, and antifibrotic drugs.

Intercalated cell of salivary gland

Intercalated duct cell: cuboidal epithelial cell lining the smallest salivary ducts between acini and striated ducts; markers K7, IP3R3, Cx26, TMEM16a, AQP5; secretory phenotype and progenitor role.

Intermediate filament

Intermediate filaments (IFs), ~10 nm cytoskeletal filaments of keratins, vimentin, desmin, GFAP, neurofilaments, and lamins, encoded by 65 human genes; they buffer mechanical stress, are apolar, and their mutations cause skin, muscle, and lamin diseases.

Interphase

Interphase is the interval between two successive cell divisions in a eukaryotic cell, comprising G1, S phase with DNA replication, and G2; it takes about 23 hours in a typical human cell.

Interphotoreceptor matrix proteoglycan

Interphotoreceptor matrix proteoglycans IMPG1 (SPACR, IPM150) and IMPG2 (SPACRCAN, IPM200) are chondroitin sulfate-rich proteoglycans forming the retinal interphotoreceptor matrix; their SEA-domain proteolysis and mutations cause vitelliform macular dystrophy and retinitis pigmentosa.

Oct 20, 2026

Interstitial cell

Interstitial cell: a morphological histology term for cells occupying the interstitium between a tissue's defining cells. Covers interstitial cells of Cajal (gut pacemakers, c-kit/ANO1), Leydig cells (testicular testosterone), and Cajal's 1891–93 usage.

Interstitial extravillous trophoblast cell

Interstitial extravillous trophoblast (iEVT, interstitial trophoblast, X cell) is the EVT subtype that invades decidual stroma, anchors the placenta, clusters around spiral arteries, and differs from endovascular EVT.

Intestinal epithelial cell

Intestinal epithelial cell: the absorptive and secretory cells (enterocytes, goblet, Paneth, enteroendocrine, tuft) lining the gut, renewed every few days from Lgr5+ crypt stem cells.

Intestine 407

Intestine 407 (INT 407, Henle-407), a human epithelial cell line established in 1955 as embryonic intestinal tissue but actually a HeLa cervical cancer derivative, ICLAC-00008, used in about 1,400 papers as normal intestine.

Intestine goblet cell

Intestine goblet cell: specialized intestinal epithelial cell secreting MUC2 mucin to form the protective mucus barrier; arises from Notch-regulated crypt stem cells, samples antigens via GAPs, and is implicated in IBD and colorectal cancer.

Intracellular chloride channel

Intracellular chloride channel: chloride-conducting channels of organelle membranes, including intracellular ClCs, bestrophins, CFTR, GPHR, and the six-member CLIC (p64) family, whose channel status is disputed.

Intracellular staining

Intracellular staining is a cytometry and microscopy technique in which cells are fixed and permeabilized so fluorescent antibodies can bind intracellular targets such as cytokines and transcription factors.

Intraflagellar transport

Intraflagellar transport (IFT): bidirectional kinesin-2 and dynein-2 driven movement of IFT-A/IFT-B protein trains along ciliary microtubules, building and maintaining cilia; discovered in Chlamydomonas, linked to ciliopathies.

Intraflagellar transport protein 20

IFT20 (intraflagellar transport protein 20) is the smallest subunit of the IFT-B ciliary transport complex, part of the IFT-B2 peripheral subcomplex, uniquely localized at both cilia and the Golgi, where GMAP210 anchors it for ciliary protein sorting.