Question
Tissue culture
Answer
Tissue culture (cell culture) is the technique of growing/maintaining cells outside the body in a controlled artificial environment, used as one of the three classical methods for propagating viruses (alongside embryonated eggs and laboratory animal inoculation), and central to diagnostic virology, vaccine production, and research.
Types: primary cell culture (freshly derived from tissue, limited passage capability, retains normal diploid karyotype); diploid cell strain (e.g., WI-38, MRC-5, retains diploid karyotype but permits extended, though still finite, passage — used for growing certain vaccines); continuous (established) cell line (e.g., HeLa, Vero cells — derived from malignant/transformed cells, capable of indefinite passage, aneuploid karyotype).
Requirements: a suitable nutrient medium (containing amino acids, vitamins, salts, glucose, often supplemented with serum), a sterile environment, appropriate temperature/CO2/humidity conditions, and (for adherent cell types) a suitable growth surface.
Detection of viral growth: cytopathic effect (CPE — visible morphological changes such as rounding, syncytium formation, cell lysis); haemadsorption (for viruses causing minimal CPE but expressing haemagglutinin on the infected cell surface); interference (detecting a non-cytopathic virus by its ability to block a second, known cytopathic virus); and direct detection of viral antigen (immunofluorescence) or nucleic acid (PCR) within infected cells.
Applications: viral isolation/diagnosis, vaccine production (many modern vaccines are grown in continuous cell lines such as Vero cells), antiviral drug testing, and cancer/general cell biology research.