Table of Contents

Terminology

The following glossary was originally published by the Tissue Culture Association Terminology Committee in 1990.31 

Anchorage-dependent cells or cultures. Cells, or cultures derived from them, which will grow, survive, or maintain function only when attached to a surface such as glass or plastic. The use of this term does not imply that the cells are normal or that they are not neoplastically transformed. 

Aneuploid. The situation in which the nucleus of a cell does not contain an exact multiple of the haploid number of chromosomes, one or more chromosomes being present in greater or lesser number than the rest. The chromosomes may or may not show rearrangements. 

Aseptic technique. Procedures used to prevent the introduction of fungi, bacteria, viruses, mycoplasma, or other microorganisms in cell, tissue, and organ cultures. Although these procedures are used to prevent microbial contamination of cultures, they also prevent cross-contamination of cell cultures as well. 

Attachment efficiency. The percentage of cells plated (seeded, inoculated) which attach to the surface of the culture vessel within a specified period of time. The conditions under which such a determination is made should always be stated. 

Autocrine cell. In animals, a cell which produces hormones, growth factors, or other signaling substances for which it also expresses the corresponding receptors. (See also endocrine and paracrine.) 

Cell culture. Term used to denote the maintenance or cultivation of cells in vitro including the culture of single cells. In cell cultures, the cells are no longer organized into tissues. 

Cell generation time. The interval between consecutive divisions of a cell. This interval can best be determined, at present, with the aid of cinephotomicrography. This term is not synonymous with population doubling time

Cell hybridization. The fusion of two or more dissimilar cells leading to the formation of a synkaryon. 

Cell line. A cell line arises from a primary culture at the time of the first successful subculture. The term implies that cultures from it consist of lineages of cells originally present in the primary culture. The terms finite or continuous are used as prefixes if the status of the culture is known. If not, the term line will suffice. The term continuous line replaces the term established line. In any published description of a culture, one must make every attempt to publish the characterization or history of the culture. If such has already been published, a reference to the original publication must be made. In obtaining a culture from another laboratory, the proper designation of the culture, as originally named and described, must be maintained and any deviations in cultivation from the original must be reported in any publication.

Cell strain. A cell strain is derived either from a primary culture or a cell line by the selection or cloning of cells having specific properties or markers. In describing a cell strain, its specific features must be defined. The terms finite or continuous are to be used as prefixes if the status of the culture is known. If not, the term strain will suffice. In any published description of a cell strain, one must make every attempt to publish the characterization or history of the strain. If such has already been published, a reference to the original publication must be made. In obtaining a culture from another laboratory, the proper designation of the culture, as originally named and described, must be maintained and any deviations in cultivation from the original must be reported in any publication. 

Chemically defined medium. A nutritive solution for culturing cells in which each component is specifiable and, ideally, is of known chemical structure. 

Clone. In animal cell culture terminology, a population of cells derived from a single cell by mitoses. A clone is not necessarily homogeneous and therefore the terms clone and cloned do not indicate homogeneity in a cell population, genetic or otherwise. 

Cloning efficiency. The percentage of cells plated (seeded, inoculated) that form a clone. One must be certain that the colonies formed arose from single cells in order to properly use this term. (See colony forming efficiency.) 

Colony forming efficiency. The percentage of cells plated (seeded, inoculated) that form a colony. 

Contact inhibition of locomotion. A phenomenon characterizing certain cells in which two cells meet, locomotory activity diminishes and the forward motion of one cell over the surface of the other is stopped. 

Continuous cell culture. A culture which is apparently capable of an unlimited number of population doublings, often referred to as an immortal cell culture. Such cells may or may not express the characteristics of in vitro neoplastic or malignant transformation. (See also immortalization.) 

Crisis. A stage of the in vitro transformation of cells. It is characterized by reduced proliferation of the culture, abnormal mitotic figures, detachment of cells from the culture substrate, and the formation of multinucleated or giant cells. During this massive cultural degeneration, a small number of colonies usually, but not always, survives and gives rise to a culture with an apparent unlimited in vitro lifespan. This process was first described in human cells following infection with an oncogenic virus (SV40). See also cell line, in vitro transformation, and in vitro senescence. 

Cryopreservation. Ultra-low temperature storage of cells, tissues, embryos, or seeds. This storage is usually carried out using temperatures below -100°C. 

Density-dependent inhibition of growth. Mitotic inhibition correlated with increased cell density.

Differentiated. Cells in culture that maintain all or much of the specialized structure and function typical of the cell type in vivo

Diploid. The state of the cell in which all chromosomes, except sex chromosomes, are two in number and are structurally identical with those of the species from which the culture was derived. 

Electroporation. Creation by means of an electrical current of transient pores in the plasmalemma usually for the purpose of introducing exogenous material, especially DNA, from the medium. 

Embryo culture. In vitro development or maintenance of isolated mature or immature embryos. 

Embryogenesis. The process of embryo initiation and development. 

Endocrine cell. In animals, a cell which produces hormones, growth factors or other signaling substances for which the target cells, expressing the corresponding receptors, are located at a distance. (See also autocrine or paracrine.) 

Epithelial-like. Resembling or characteristic of, or having the form or appearance of, epithelial cells. In order to define a cell as an epithelial cell, it must possess characteristics typical of epithelial cells. Often one can be certain of the histologic origin and/or function of the cells placed into culture and, under these conditions, one can be reasonably confident in designating the cells as epithelial. The individual reporting on such cells should use as many parameters as possible in assigning this term to a culture. Until a rigorous definition is possible, it is more correct to use the term epithelial-like. 

Euploid. The situation in which the nucleus of a cell contains exact multiples of the haploid number of chromosomes. 

Feeder layer. A layer of cells (usually irradiated or mitomycin-C treated) that are nondividing but metabolically active, upon which a fastidious cell type is cultured. 

Finite cell culture. A culture which is capable of only a limited number of population doublings after which the culture ceases proliferation. (See in vitro senescence.) 

Heterokaryon. A cell possessing two or more genetically different nuclei in a common cytoplasm, usually derived as a result of cell-to-cell fusion. 

Heteroploid. A culture whose cells contain chromosome number other than the diploid number. This is a term used only to describe a culture and is not used to describe individual cells. Thus, a heteroploid culture would be one which contains aneuploid cells. 

Histiotypic. The in vitro resemblance of cells in culture to a tissue in form, function, or both. For example, a suspension of fibroblast-like cells may secrete a glycosaminoglycan-collagen matrix and the result is a structure resembling fibrous connective tissue, which is, therefore, histiotypic. This term is not meant to be used along with culture. Thus, a tissue culture system demonstrating form and function typical of the cells in vivo would be said to be histiotypic. 

Homokaryon. A cell possessing two or more genetically identical nuclei in a common cytoplasm, derived as a result of cell-to-cell fusion. 

Hybridoma. The cell which results from the fusion of an antibody-producing tumor cell (myeloma) and an antigenically stimulated normal plasma cell. Such cells are constructed because they produce a single antibody directed against the antigen epitope which stimulated the plasma cell. This antibody is referred to as a monoclonal antibody. 

Immortalization. The attainment by a cell culture, whether by perturbation or intrinsically, of the attributes of a continuous cell line. An immortalized cell is not necessarily one which is neoplastically or malignantly transformed. 

In vitro senescence. The inability of a vertebrate cell culture to grow beyond a finite number of population doublings. Neither invertebrate nor plant cell cultures exhibit this property. 

In vitro transformation. A heritable change occurring in cells in culture, either intrinsically or from treatment with chemical carcinogens, oncongenic viruses, irradiation, transfection with oncogenes, etc., which leads to the acquisition of altered morphological, antigenic, neoplastic, proliferative, or other properties. This expression is distinguished from in vitro neoplastic transformation in that the alterations occurring in the cell population may not always include the ability of the cells to produce tumors in appropriate hosts. The type of transformation should always be specified in any description. 

Organ culture. The maintenance or growth of organ primordia or the whole or parts of an organ in vitro in a way that may allow differentiation and preservation of the architecture and/ or function. 

Paracrine. In animals, a cell which produces hormones, growth factors or other signaling substances for which the target cells, expressing the corresponding receptors, are located in its vicinity, or in a group adjacent to it. (See also autocrine and endocrine.) 

Passage. The transfer or transplantation of cells, with or without dilution, from one culture vessel to another. It is understood that any time cells are transferred from one vessel to another, a certain portion of the cells may be lost, and therefore dilution of cells, whether deliberate or not, may occur. This term is synonymous with subculture. 

Passage number. The number of times the cells in the culture have been subcultured or passaged. In descriptions of this process, the ratio or dilution of the cells should be stated so that the relative cultural “age” can be ascertained. 

Plating efficiency. This term originally encompassed the terms attachment efficiency, cloning efficiency, and colony forming efficiency; it is now better to use one or more of them in its place because plating is not sufficiently descriptive. (See attachment efficiency, cloning efficiency, and colony forming efficiency.) 

Population density. The number of cells per unit area or volume of a culture vessel, or the number of cells per unit volume of medium in a suspension culture. 

Population doubling level. The total number of population doublings of a cell line or strain since its initiation in vitro. This term is synonymous with cell generation time. 

Population doubling time. The interval, calculated during the logarithmic phase of growth in which cells double in number; for example, 1.0 x 106 cells increase to 2.0 x 106 cells. This term is not synonymous with cell generation time. 

Primary culture. A culture started from cells, tissues, or organs taken directly from organisms. A primary culture may be regarded as such until it is successfully subcultured for the first time. It then becomes a cell line. 

Pseudodiploid. The condition in which the number of chromosomes in a cell is diploid but, as a result of chromosomal rearrangements, the karyotype is abnormal and linkage relationships may be disrupted. 

Saturation density. The maximum cell number attainable, under specified culture conditions, in a culture vessel. This term is usually expressed as the number of cells per square centimeter in a monolayer culture or the number of cells per cubic centimeter in a suspension culture. 

Suspension culture. A type of culture which will grow and can be maintained without attaching to a surface, such as glass or plastic. 

Transfection. The transfer, for the purpose of genomic integration, of foreign DNA into cells in culture. The traditional microbiological usage of this term implied that the DNA being transferred was derived from a virus. The definition as stated here describes the general transfer of DNA irrespective of its source. 

Undifferentiated. With animal cells, this is the state wherein the cell in culture lacks the specialized structure and/or function of the cell type in vivo.