Cross-Contamination by Other Cell Lines

The seriousness of cross contamination, while not as common as microbial contamination, cannot be overstated. The validity of experimental results from cultures having inter- or intra-species contamination is at least questionable, and their use can lead to the embarrassment of having to retract published results.

Whenever the invading cell is better adapted to the culture conditions and thus faster growing than the original cells, it can completely replace them. Because of similar morphology of different cell lines and wide morphological variations of the same cell line that can be caused by varying culture conditions; it is impossible to rely only on microscopic observation to screen for cross-contamination of cultures.

Since the late 1950´s, it became apparent that cell lines can be cross-contaminated by other cell lines. By using isoenzyme analysis it has been shown in 1967 that HeLa cells had contaminated, or better completely replaced, 20 cell lines analysed (Gartler, 1968). Another study on 246 cell lines showed that nearly 30 % were incorrectly designated: 14 % were the wrong species and 25 % of the human cell lines were in fact HeLa cells (Stulberg et al., 1976). In principal, any robust and often used cell line, e.g. HEK293, may have the potential to frequently contaminate others. Simple accidents are one of the most common means by which other cell lines gain entry into cultures. In general, cross-contamination by other cell lines can be intra- or interspecies specific, as such, human cell lines may contain mouse or rat cells and vice versa. As a matter of fact, intra-species contamination is more difficult to detect. One possibility is to test for additional cell markers such as presence of Y-chromosome sequences, viral sequences or single nucleotide polymorphisms (SNPs).

The McCT assay is able to detect species from most frequently used cell line, including human, monkey, mouse, rat, Chinese hamster, rabbit, Guinea pig, feline and canine cells. At the same time, the gender of human/monkey, mouse and rat cells can be determined, giving additional information on the cell line purity. But also virus sequences that are present or had been used for immortalisation of the cell line can be used as additional cell line markers. The following table exemplarily shows some cell lines and potential markers.

Multiplexion - Advanced Detection