RAW 264.7 is a cell line that functions as a fundamental tool in biological research, particularly within the study of the immune system. This standardized model allows scientists to investigate how immune cells respond to pathogens, toxins, and potential drug compounds in a controlled laboratory setting. A cell line is a population of cells that can be grown indefinitely outside the body, providing a consistent system for experimentation. As an immortalized cell model, RAW 264.7 provides a proxy for understanding the behavior of a specific type of white blood cell in mice, making it standard for studying immunology, inflammation, and toxicology.
Origin and Establishment of the Cell Line
The RAW 264.7 cell line originated from a tumor in a male BALB/c mouse. The tumor was induced using the Abelson murine leukemia virus (A-MuLV). Researchers at the National Cancer Institute established the resulting cells as a stable line in the 1970s, after the viral transformation caused them to acquire the ability to divide endlessly.
The indefinite lifespan of RAW 264.7 cells is invaluable, eliminating the need to constantly harvest fresh cells from live animals. This consistency minimizes the variability inherent in using primary cells, ensuring that experiments performed over long periods can be compared directly. The cells retained many functional characteristics of the original immune cell, making them a suitable model for studying macrophage behavior.
Defining Characteristics of RAW 264.7
RAW 264.7 cells are classified as a macrophage-like line, representing a type of immune cell responsible for engulfing and digesting cellular debris, foreign substances, and cancer cells. In culture, these cells exhibit an adherent growth pattern, meaning they naturally attach themselves to the surface of the culture flask or plate. Their morphology is typically round or oval during normal culture, though they can become spindle-shaped when highly polarized or activated.
A defining feature of these cells is their ability to perform phagocytosis, a process where they actively consume foreign particles. Researchers test this ability by observing the cells engulf materials such as latex beads or zymosan. This function, along with pinocytosis (cellular drinking), confirms they maintain core innate immune system functions. Although they are not primary cells, they retain enough biological fidelity to serve as a high-utility model for studying immune mechanisms.
Primary Role in Scientific Research
RAW 264.7 is a preferred model for high-throughput screening in immunology and pharmacology. Researchers frequently use these cells to rapidly test hundreds or thousands of compounds, such as new drug candidates or natural extracts, for their potential effects on immune responses. This initial screening process is significantly more cost-effective and efficient than beginning with complex animal models.
A significant application is in toxicology studies, assessing how harmful substances affect immune cell function. By exposing RAW 264.7 cells to various environmental toxins or pollutants, researchers can quickly evaluate the potential for a substance to cause an inflammatory reaction or oxidative stress. This provides information about the safety and immunotoxicity of new materials before they proceed to more involved testing.
The cells are extensively used in inflammation research to understand the pathways regulating the body’s response to injury or infection. Studies often focus on finding compounds that can moderate or suppress the inflammatory reaction, offering pathways to develop treatments for chronic inflammatory diseases. The ability to precisely compare results across different laboratories accelerates the pace of discovery. Although mouse cell results do not perfectly mirror human biology, their use as a reliable initial proxy model streamlines the entire research pipeline.
Activation and Immune Signaling
To mimic infection or injury, researchers must intentionally “activate” the RAW 264.7 cells. The most common method involves stimulating them with lipopolysaccharide (LPS), a component found in the outer membrane of many types of bacteria. LPS acts as a danger signal that triggers the cells to initiate an immune response, reflecting how the body reacts to bacteria. This stimulation activates complex internal molecular pathways, such as the NF-κB and MAPK pathways, that drive the immune reaction.
Once activated by LPS, the cells begin the mass production and release of various chemical messengers that drive inflammation. Among the substances produced are pro-inflammatory cytokines, small proteins that regulate immune cell communication. Specific examples include Tumor Necrosis Factor-alpha (TNF-alpha) and Interleukin-6 (IL-6), which escalate inflammation.
Another molecule released upon activation is nitric oxide (NO). Macrophages use nitric oxide as an antimicrobial agent to kill pathogens and tumor cells. The production of NO is catalyzed by an enzyme called inducible nitric oxide synthase (iNOS), which is significantly upregulated following LPS exposure. By measuring the release of these inflammatory molecules, researchers can determine whether a test compound is capable of suppressing or enhancing the immune reaction.