= L929 cell
{c}
= L929 cell line
{c}
{synonym}
An \b[<L929 cell>] belongs to the murine <cell line> commonly catalogued as NCTC clone929 or ATCC CCL-1, derived from strainL. The culture collection describes fibroblast morphology and adherent growth. It records the clone's establishment by single-cell isolation in1948 from the parent strain's 95th <subculture> generation.<NCTC clone 929 CCL-1 record by ATCC>[CCL-1 record, Morphology, Growth properties and Derivation]{ref} A clone describes ancestry; it does not mean that every later descendant has an unchanged <genome> or identical behaviour.
The <cell line> supplies a reproducible experimental population for defined assays, rather than a complete model of normal connective <tissue>. One motivating use is a <bioassay> in which <TNF-alpha> produces a cellular response and <etanercept> counteracts that challenge. A United States Pharmacopeia application note uses L929 murine fibroblasts in this assay context, with a <cell viability> readout and validation of response comparisons.<Etanercept for Bioassays reference-standard application note by United States Pharmacopeia>[How and when to use the reference standard; Method validation; Figure2]{ref}
An original normalization example distinguishes response recovery from raw signal. Suppose matched, blank-corrected signals are $1.00$ for an unchallenged control, $0.20$ for the challenge without inhibitor and $0.60$ for the tested preparation. Fractional recovery between those endpoints is
$$
\frac{0.60-0.20}{1.00-0.20}=0.50.
$$
This is neither the raw signal ratio $0.60/1.00$ nor a direct count of bound TNF molecules. It is a functional comparison under the stated measurement model. Cell number, culture history, sensitivity to the challenge and per-cell readout behaviour must remain appropriate for interpreting the comparison. The chosen signals are illustrative, not values from the reference-standard note.
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