GM-CSF
Meaning of GM-CSF: A signal that tells the marrow to produce the cells that fight infection, and that doubles as an alarm molecule in inflamed tissue.
Definition of GM-CSF
GM-CSF is a natural signalling protein that drives bone marrow stem cells to produce granulocytes and macrophages, the white cells that engulf and destroy microbes. It also activates those cells once they are mature and helps the immune system present fragments of invaders to lymphocytes. A manufactured version is given as a drug to shorten the period of low white cell counts after chemotherapy.
What does the name describe?
Granulocyte-macrophage colony-stimulating factor is a literal description of how it was found. Marrow cells grown in a dish form small colonies, and adding this substance made colonies of granulocytes and macrophages appear. Several such factors were identified the same way and named for the colonies they stimulated. The name records an observation in a laboratory dish rather than the molecule's role in the body, which turned out to be broader.
How does it differ from the related factor?
| GM-CSF | G-CSF | |
|---|---|---|
| Cells stimulated | Granulocytes and macrophages | Granulocytes almost exclusively |
| Effect on immune activation | Strong, also activates presenting cells | Mainly numerical |
| Typical tolerability | More fever, aches and fluid retention | Better tolerated |
That difference in tolerability is why the narrower factor became the routine choice for raising counts after chemotherapy, while this one is used more selectively.
What else does it do?
Outside the marrow it behaves as an inflammatory cytokine. Tissue cells release it where there is injury or infection, and it recruits and activates arriving white cells, sharpening their killing and their ability to present material to lymphocytes. That property has been exploited deliberately: it is built into some cancer vaccines and engineered viruses to draw immune attention toward a tumor. The same property makes excess of it damaging, and it is implicated in inflammatory lung and joint disease, where blocking it rather than giving it is the aim.
Is the drug the same molecule?
Not quite. Sargramostim is a manufactured version made in yeast, and it differs from the human protein at one position and in its sugar coating. It is a distinct product with its own properties, so treating the drug name and the natural factor as interchangeable is inaccurate even though the two are usually discussed together.
Also known as
Used in a sentence
GM-CSF was incorporated into the vaccine construct to recruit antigen presenting cells.
Good to know
Sargramostim is a manufactured version that differs from the natural protein in sequence and sugar coating, so the drug and the human cytokine are not strictly the same molecule.