Cell line longevity — what is the term for cell lines that acquire the ability to be subcultured indefinitely in vitro (beyond the finite lifespan of primary cells)?

Introduction / Context:
Most primary mammalian cells have a limited replicative lifespan (the Hayflick limit). Some lines bypass this limit and can be maintained indefinitely. Correct terminology is essential for experimental design, quality control, and regulatory documentation.

Given Data / Assumptions:

• The question describes cells that can be subcultured indefinitely.
• No specific species or transformation mechanism is provided.
• We distinguish among primary, secondary, and continuous (established) lines.

Concept / Approach:

Cells that proliferate without senescence under culture conditions are typically called “established” or “continuous” cell lines. They may arise via spontaneous immortalization, viral oncogenes, or engineered telomerase expression. Primary and secondary lines are finite and senesce after limited passages.

Step-by-Step Solution:

Verification / Alternative check:

Cell culture texts and ATCC documentation consistently use “continuous/established” for immortal cell populations capable of unlimited passages.

Why Other Options Are Wrong:

Primary and secondary are finite; “propagated cell lines” is nonspecific; terminally differentiated cultures do not divide indefinitely.

Common Pitfalls:

Confusing “long-term culture” with true immortalization; assuming serum concentration alone determines lifespan.

Final Answer:

Established cell lines (continuous cell lines)