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Short answer
THP-1 is a human monocytic cell line: a population of cells established in 1980 from the blood of a one-year-old boy with acute monocytic leukemia and propagated in culture ever since. “THP cell line” and “THP 1” refer to the same line. The details that matter at the bench are its origin, the medium the repository lists for it, and the fact that published values for properties such as doubling time differ between sources.
Definition and scope: what a cell line is
Thermo Fisher’s cell culture reference separates two things. In primary culture, “cells are directly isolated from tissues and established in vitro for the first time.” A cell line, by contrast, is “a defined population of cells grown and proliferated repeatedly in vitro.” Subculturing (passaging) is the routine step that keeps such a population going; see the guide to cell passaging for the general principles.
The same reference describes two broad kinds. Finite cell lines “usually divide only a limited number of times before losing their ability to proliferate,” while “a continuous cell line is a finite cell line that has undergone a process called transformation.” THP-1 is a leukemia-derived line; Cellosaurus lists it as a cell line from a childhood acute monocytic leukemia.
Cell line, cell lines, definition of a cell line
These phrasings all ask the same question, and the answer above covers them. What changes from line to line is the identity record: species, tissue, donor, disease, culture conditions and a unique identifier. The sections below show what that record looks like for THP-1.
What THP-1 is
Tsuchiya and colleagues described the line in the International Journal of Cancer in 1980 (PMID 6970727), titled “Establishment and characterization of a human acute monocytic leukemia cell line (THP-1).” It came from the blood cells of a boy with acute monocytic leukemia. The authors reported Fc and C3b receptors, no surface or cytoplasmic immunoglobulins, lysozyme production, phagocytosis of latex particles and sensitized sheep erythrocytes, and monocytic characteristics retained over 14 months in culture.
The ATCC record (catalog TIB-202) lists the organism as Homo sapiens, tissue as peripheral blood, a 1-year-old male donor, disease acute monocytic leukemia, and monocyte morphology. Cellosaurus (accession CVCL_0006) lists the synonyms THP1, THP 1, THPI and Tohoku Hospital Pediatrics-1, and the key genetic features NRAS p.Gly12Asp (heterozygous), TP53 p.Arg174fs*3 and a KMT2A-MLLT3 fusion.
How it is used and cultured
ATCC lists the growth properties as “adherent and/or suspension,” the medium as ATCC-formulated RPMI-1640 (30-2001) with fetal bovine serum to a final concentration of 10% and 2-mercaptoethanol at 0.05 mM, and an approximate doubling time of 26 hours. For storage, ATCC specifies the vapor phase of liquid nitrogen (at or below -130 °C) and notes that storage at -70 °C reduces viability; the guide to cryopreservation media covers freezing media in general.
A major reason labs use THP-1 is that it can be changed from a monocyte-like cell into a macrophage-like cell. ATCC states that monocytic differentiation can be induced with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Cellosaurus describes the same behavior as differentiation into macrophage-like cells upon stimulation with PMA. TPA and PMA are two names for the same compound, so protocols using either name are describing the same reagent.
Assays run on such cells, for example MTT viability measurements, depend on knowing the line is what its label says, which the next sections address.
Source-to-source differences
THP-1 records do not agree on every property, and the differences are worth knowing before you plan an experiment or write a methods section.
| Property | What the sources say | Source |
|---|---|---|
| Doubling time | About 26 hours | ATCC TIB-202 |
| Doubling time | Cellosaurus records three differing comments: 60-70 hours (PubMed 6970727), 26 hours (PubMed 25984343) and about 35-50 hours (DSMZ ACC-16) | Cellosaurus CVCL_0006 |
| HLA type | Tsuchiya 1980 reported HLA-A2, -A9, -B5, -DRW1 and -DRW2; a later paper (PubMed 22674354) is titled “Molecular characterisation of the monocytic cell line THP-1 demonstrates a discrepancy with the documented HLA type” | PubMed 6970727; PubMed 22674354 |
| STR profile | ATCC lists, among its loci: Amelogenin X,Y; CSF1PO 11,13; D13S317 13; D5S818 11,12; D7S820 10; TH01 8,9.3; TPOX 8,11; vWA 16. Cellosaurus lists these and further loci, including D1S1656 16,17 and D2S441 10,11 | ATCC TIB-202; Cellosaurus CVCL_0006 |
Practical reading: a single “doubling time of THP-1” is a property of a particular supplier’s stock under particular conditions, not a constant of the line. Record the source and conditions you measured under rather than copying a published figure.
Where it matters for labs and supply decisions
- Identity records. Cellosaurus assigns THP-1 the identifier CVCL_0006. A stable identifier lets a methods section name the exact line; see RRID.
- Authentication. The STR profile published by the repository is the reference a lab compares its own cells against; see authentication of key resources.
- Obtaining a vial. A line obtained from a repository or another laboratory may come with terms of transfer; see material transfer agreements.
- Contamination. Thermo Fisher’s reference states that basic techniques of cell culture include aseptic handling to prevent contamination; see cell culture contamination.
Common misunderstandings
“THP cell line” and “THP-1” are different lines
Cellosaurus lists “THP 1” and “THP1” as synonyms of THP-1, so searches for “THP cell line” are almost always looking for this line.
THP-1 is a primary monocyte
It is not. It is a leukemia-derived line with documented mutations. Primary culture, per the definition above, starts from cells isolated from tissue.
There is one doubling time
See the table: reported values range from about 26 to 60-70 hours depending on the source.
TPA and PMA are different inducers
They are two names for the same compound.
FAQ
What is a cell line?
A defined population of cells grown and proliferated repeatedly in vitro, as opposed to primary culture, where cells are first isolated from tissue.
What is the definition of a cell line, and what are cell lines?
The same thing in plural: separate populations, each with its own origin and identity record, such as THP-1 (CVCL_0006).
What is the THP-1 cell line?
A human monocytic line established in 1980 from a one-year-old boy with acute monocytic leukemia, and available from ATCC as TIB-202.
What does THP stand for?
Cellosaurus lists “Tohoku Hospital Pediatrics-1” among the synonyms.
Sources
- ATCC, THP-1 (TIB-202) product page, https://www.atcc.org/products/tib-202, checked 2026-10-29.
- Cellosaurus, THP-1 (CVCL_0006), https://www.cellosaurus.org/CVCL_0006, checked 2026-10-29.
- Tsuchiya S, et al. Establishment and characterization of a human acute monocytic leukemia cell line (THP-1). Int J Cancer. 1980;26(2):171-176. https://pubmed.ncbi.nlm.nih.gov/6970727/, checked 2026-10-29.
- Thermo Fisher Scientific, Introduction to cell culture (Gibco cell culture basics), https://www.thermofisher.com/us/en/home/references/gibco-cell-culture-basics/introduction-to-cell-culture.html, checked 2026-10-29.
