A sensitive and quantitative microassay for the detection of mycoplasma contamination: inhibition of IL-2 dependent cell line proliferation.

A simple, rapid and sensitive microassay for mycoplasma detection in cell culture is reported. The assay is based on the fact that culture supernatants from contaminated cells inhibit [3H]thymidine incorporation by an IL-2 dependent mouse cytotoxic T cell line (CTLL). The mechanism of inhibition is related to the production by several mycoplasma strains of a pyrimidine-specific nucleoside phosphorylase which can degrade the radiolabelled thymidine used for the measurement of DNA synthesis. These strains were the commonest contaminants in cultures of 24 cell lines from 5 different sources. To establish the sensitivity of the test to detect mycoplasmas we have also used the inhibition assay to monitor the clearance of mycoplasma from 2 contaminated cell lines.