Non-immortal cell lines, also known as primary cell lines, are cells that are directly isolated from a tissue and have not been modified to bypass senescence, the process that limits the number of times a cell can divide.

Primary cell lines retain many of the characteristics of the cells in the original tissue, including normal gene expression patterns and responses to signals and treatments. This makes them a valuable tool for studying normal cell biology and for modeling diseases in a context that is more physiologically relevant than immortal cell lines.

However, primary cell lines also have limitations. They typically have a finite lifespan and can only be passaged a limited number of times before they undergo senescence and stop dividing. This can make them more difficult to work with, especially for long-term experiments.

Moreover, primary cells often require more specialized growth conditions than immortal cell lines, and they can show greater variability between batches, especially if they are isolated from different individuals.

It’s important to note that while primary cell lines provide a more physiologically relevant model than immortal cell lines, they still do not fully recapitulate the complexity of an intact organism or even of a tissue. As with any model system, the choice between using primary or immortal cell lines depends on the specific research question and the strengths and weaknesses of each option.