Animal Tissue Culture and Hybridoma Technolog - The term tissue culture refers to the culture of whole organs, tissue fragments as well as dispersed cells on a suitable nutrient medium. It can be divided into
(1) organ culture and
(2) cell culture mainly on the basis of whether the tissue organisation is retained or not.
Freshly isolated cell cultures are called primary cultures; they are usually heterogeneous and slow growing, but are more representative of the tissue of their origin both in cell type and properties. Once a primary culture is subcultured, it gives rise to cell lines, which may either die after several subcultures (such cell lines are known as finite cell lines) or may continue to grow indefinitely (these are called continuous cell lines).
Usually, normal tissues give rise to finite cell lines, while tumours give rise to continuous cell lines. But there are several examples of continuous cell lines, which were derived from normal tissues and are themselves nontumorigenic, e.g., MDCK dog kidney, 3T3 fibroblasts, etc.
The evolution of continuous cell lines from primary cultures is supposed to involve a mutation, which alters their properties as compared to those of finite lines.