Written and maintained by CASRAI Editorial Board
Last updated
Short answer: MRC-5 is a finite human diploid cell line of lung fibroblasts, isolated in 1966 from the lung tissue of a 14-week-old male fetus. It is not immortal: ATCC reports 42 to 46 population doublings before senescence. It is used in research, virus work and as a vaccine production substrate. This page is general reference information, not medical advice.
Reader task: researchers and lab staff who meet “MRC-5” on a repository sheet or in a methods section and need to know what the line is, why its passage number matters and what to record when it arrives.
Definition and scope
MRC-5 (also written MRC5 or “MRC 5”) is a fibroblast line derived from fetal lung. The Cellosaurus entry for MRC-5 PDL13 (CVCL_E5ZR) records the cells as Homo sapiens, male, 14 fetal weeks, from lung, and classifies the line as a finite cell line in the group vaccine production cell line. ATCC (catalogue number CCL-171) credits the isolation to J. P. Jacobs in 1966 and describes the donor as a 14-week male embryo. The original characterisation was published by Jacobs, Jones and Baille in Nature (1970) as “Characteristics of a human diploid cell designated MRC-5”.
Are MRC-5 cells human diploid cells?
Yes. MRC-5 is described in the literature as a human diploid cell line, meaning it carries the normal paired human chromosome set rather than the altered karyotype typical of many continuous lines. It is human-derived, which is one reason it is discussed as an alternative to non-human substrates such as Vero cells (see the comparison below).
MRC-5, MRC 5 and MRC5, PDL12 and PDL13
The spellings are variants of the same name. Repository records also name a specific population doubling level: Cellosaurus lists MRC-5 PDL13 (CVCL_E5ZR) with MRC-5 PDL12 (CVCL_JF54) as its parent, and cites the 2018 proposal for a second replacement seed stock for the WHO reference cell bank (Hawkins and Stylianou, WHO/BS/2018.2347). That is why searches such as “MRC-5 pd13” return culture-collection entries: the number is the doubling level of the banked stock, not a different cell line.
What are the three types of cell lines?
Sources do not all use the same scheme, so this page only states what it sourced. Cellosaurus labels MRC-5 a finite cell line: it divides a limited number of times and then stops. The contrast is a continuous line, which can be passaged indefinitely, as with HeLa cells or the HCT116 line. Where a source counts three types, check which scheme it uses before comparing.
How MRC-5 is used in practice
ATCC lists efficacy testing, use as a transfection host and viruscide testing among the applications of CCL-171, and recommends EPA Method MB-39-01 for human coronavirus virucidal testing. Its handling instructions for the line are:
- Growth medium: EMEM with 10% fetal bovine serum.
- Atmosphere: 37 °C, 95% air and 5% CO2.
- Subculture: split 1:2 to 1:5, or seed at 1.0 x 10^4 to 6.0 x 10^4 viable cells per cm2.
- Medium renewal: once or twice a week.
- Freezing: medium with 5% DMSO.
- Lifespan: 42 to 46 population doublings before senescence.
The finite lifespan is the practical point. A 2025 paper in Archives of Razi Institute (Abbasi et al.) notes that MRC-5 shows reduced efficiency and genetic changes after extensive passaging. Cells beyond the documented window should not be treated as equivalent to early-passage stock.
Is MRC-5 in vaccines?
Are MRC-5 cells in vaccines? What vaccines have MRC-5?
MRC-5 is used as a cell substrate, meaning viruses are grown in the cells during manufacture. Abbasi et al. state that human diploid cells are used for hepatitis A, varicella and polio vaccines, and Cellosaurus assigns MRC-5 to the vaccine production cell line group. Which specific products use MRC-5, and what residual material they contain, is set out in each product’s own package insert, so consult those documents rather than a summary list. Nothing here is a recommendation for or against any vaccine.
Is MRC-5 ethical?
This is a question about values, and this page does not judge it. The factual record is that the line was derived in 1966 from fetal lung tissue and that repositories distribute it from banked stocks, including a WHO reference cell bank. Questions about institutional approval for using human-derived cells in your work belong with your institutional biosafety committee and ethics office.
How is MRC-5 obtained? Is it still used today?
Researchers obtain the line from repositories, not from tissue. ATCC supplies it as CCL-171, and the culture-collection and bank records that appear for this query include Cellosaurus (CVCL_E5ZR), JCRB9008 and RIKEN BRC RCB0218. It remains in current use: the 2025 Razi Institute study used it as the reference line against which a new human diploid cell line was compared.
Comparison: MRC-5 against alternatives (sourced rows only)
| Comparison | What the source states | Source |
|---|---|---|
| MRC-5 vs Vero | Human diploid cells are described as a safer alternative to Vero because of concern about non-human DNA. | Abbasi et al. 2025 |
| MRC-5 vs RAZI-HDC | In an RSV study, MRC-5 gave 2.5 log TCID50/mL and RAZI-HDC 2.4685 log TCID50/mL (p = 0.78, not significant). | Abbasi et al. 2025 |
| MRC-5 vs passage | Reduced efficiency and genetic changes reported after extensive passage; ATCC documents 42 to 46 doublings. | Abbasi et al. 2025; ATCC CCL-171 |
| MRC-5 vs continuous lines | Finite lifespan versus indefinite passaging. | Cellosaurus category |
Searches for MRC-5 also surface WI-38, another human diploid fibroblast strain. For fibroblast biology generally see fibroblast functions.
Receiving-checklist for MRC-5 stocks
- Record the population doubling level stated on the vial or sheet (for example PDL13) and the supplier’s catalogue number.
- Track passages and estimated cumulative doublings from that point against the 42 to 46 doubling window.
- Use the supplier’s stated medium and atmosphere (ATCC: EMEM with 10% FBS, 37 °C, 5% CO2).
- Confirm the biosafety level with the supplier datasheet and your institution. ATCC’s own pages are not consistent enough to quote a single level here; see the BSL-2 definition for what a given level implies.
- Bank early-passage vials so that later work can return to a low doubling level.
Common misunderstandings
- “MRC-5 is immortal like HeLa.” No: it is finite, with a documented doubling limit.
- “MRC-5 pd13 is a different line.” No: it is a banked doubling level of the same line.
- “Using MRC-5 means fresh fetal tissue is needed.” Repositories supply the line from banked stocks.
Frequently asked questions
Are MRC-5 human diploid cells? Yes, human diploid lung fibroblasts (see above).
Is MRC-5 in vaccines? It is a vaccine production substrate; check each product’s package insert.
Is MRC-5 still used today? Yes, including as a reference line in 2025 research.
How long can MRC-5 be cultured? ATCC reports 42 to 46 population doublings before senescence.
Sources
- Cellosaurus, MRC-5 PDL13 (CVCL_E5ZR), https://www.cellosaurus.org/CVCL_E5ZR, read 2026-11-07.
- ATCC, MRC-5 (CCL-171), https://www.atcc.org/products/ccl-171, read 2026-11-07.
- Abbasi et al., Archives of Razi Institute 2025;80(1):51-59, PMC12426423, read 2026-11-07.
- Jacobs JP, Jones CM, Baille JP. Characteristics of a human diploid cell designated MRC-5. Nature 1970.
