This really isn't that surprising and has been known for years. Lots of kids in grad school were doing experiments with cells at >200 passages that were obvious

This really isn't that surprising and has been known for years. Lots of kids in grad school were doing experiments with cells at >200 passages that were obviously contaminated with mycoplasma. I think they knew it, but their HIV research had always been done that way. I'm guessing if they went back to lower passage / non-contaminated cell lines their results would change. Similar thinking from the source [1]: > Why does ATCC continue to distribute HeLa Contaminated Cell Lines? > ATCC continues to distribute these cell lines, even though they have been shown to be contaminated with HeLa, because researchers need them for purposes beyond use as models for specific disease/original source tissue. Beyond that, certain cell lines started out as contaminated [2]: > In the earliest stocks available, the level of contamination was 0.6%. [1] https://www.atcc.org/Global/FAQs/3/6/HeLa%20contaminated%20Cell%20Lines-1207.aspx https://www.atcc.org/Global/FAQs/3/6/HeLa%20contaminated%20C... [2] https://www.atcc.org/Products/All/CRL-1593.2.aspx#characteristics https://www.atcc.org/Products/All/CRL-1593.2.aspx#characteri...