Level 1 - Absolute Beginner

Our blood has cells that fight illness. They start inside the bone. The bone is like a small factory.

Scientists in the United States grow young immune cells in the lab. These young cells can make more cells.

They add a new part to the cells. The new part helps the cells find cancer. Then the cells attack it.

The team tested this in mice and in lab cells. It is not a medicine for people yet. More work is needed.

cell

a very small living part of the body

blood

the red liquid inside the body

bone

a hard part inside the body

factory

a place that makes many things

lab

a room where scientists work

cancer

a bad illness with cells that grow too much

mice

more than one mouse, a small animal

medicine

something you take to get well

Level 2 - Elementary

Inside your bones there is a kind of factory. It makes the cells that fight infection. Some of these cells are called macrophages, and they eat germs and clean up damaged tissue. Before a macrophage is ready for work, it begins as a younger cell called a progenitor.

A team at the Keck School of Medicine of USC has found a way to grow large numbers of one kind of progenitor in the laboratory. These cells are called granulocyte-monocyte progenitors, or GMPs. A special mix of chemicals keeps the cells alive and copying themselves, and stops them from growing up too soon.

The scientists then added a receptor called a CAR to the cells. A CAR works like a label reader: it helps the cell notice a marker on cancer cells. Some of the cells also carried an extra signal that calls other immune cells to come and help.

In mice, the engineered cells moved into the bone marrow and made more immune cells there. They slowed blood cancers and solid tumours, and in mice with an immune disease they brought back the ability to fight bacteria. All of this was done in mice and in human and mouse cells in the laboratory, so it is not a treatment for people.

bone marrow

the soft material inside bones where blood cells are made

macrophage

an immune cell that eats germs and cleans up damaged tissue

progenitor

a young cell that later becomes a more grown up cell

laboratory

a place where scientists do experiments

receptor

a part on a cell that notices something outside the cell

marker

a sign on a cell that tells you what kind of cell it is

tumour

a lump made of cells that grow too much

bacteria

very small living things that can cause infection

Level 3 - Intermediate

Cell therapies that use engineered immune cells have changed the treatment of some blood cancers, but they are difficult to manufacture. Each dose is usually built one patient at a time from mature cells, and mature macrophages are especially awkward material: they are hard to expand, hard to modify and hard to freeze, and they tend to clear from the body quickly.

Reporting in the journal Cell, a USC Stem Cell led team at the Keck School of Medicine of USC describes a different approach, which is to start one step earlier in the production line. Using a defined chemical mix, the researchers kept granulocyte-monocyte progenitors, or GMPs, alive and multiplying in the laboratory for long periods while blocking their maturation, then engineered them with a chimeric antigen receptor, or CAR, aimed at a marker on cancer cells.

In mice, the engineered progenitors settled in the bone marrow and produced further engineered immune cells. The CAR-GMPs slowed disease in both blood cancers and solid tumours, and the effect was stronger when the cells also carried an extra immune activating signal designed to draw in and stimulate nearby immune cells, including T cells. In a mouse model of chronic granulomatous disease, GMPs restored the animals' ability to fight bacterial infection.

The caveat matters. This is early, preclinical research carried out in mice and in human and mouse cells, and no human trials have been reported. Safety and effectiveness in people still have to be established, especially if the cells persist and keep producing immune cells over time. Qi-Long Ying, the corresponding author, said that under the right conditions GMPs can also self renew, which offers a scalable starting point for cell therapies; self renewal in the blood system had been thought to belong mainly to hematopoietic stem cells.

preclinical

describing research done in cells or animals before any testing in people

progenitor

an immature cell that can divide and later become a specialised cell

chimeric antigen receptor

an engineered receptor, called a CAR, that makes a cell recognise a chosen target

maturation

the process by which a young cell becomes a fully developed one

bone marrow

the tissue inside bones where blood and immune cells are produced

solid tumour

a cancer that forms a mass of tissue rather than circulating in the blood

self renew

to divide in a way that produces more cells of the same kind

hematopoietic stem cell

a blood forming stem cell that can renew itself and make all blood cell types

Level 4 - Advanced

Cell therapy has a manufacturing problem that its clinical successes have largely obscured. The engineered immune cells that transformed treatment for several blood cancers are typically produced one patient at a time from mature cells, and mature macrophages are an unforgiving raw material: they resist expansion, resist modification, tolerate freezing poorly, and tend to clear from the body before they can do sustained work. The bottleneck is not the biology of recognising a tumour cell; it is the industrial question of where the cells come from.

A study published in the journal Cell, from a USC Stem Cell led team at the Keck School of Medicine of USC with collaborators at Stanford, Creighton, Harvard Medical School and the Dana-Farber Cancer Institute, moves one step back along the developmental production line. First author Shi Yue and corresponding author Qi-Long Ying used a defined chemical mix to keep granulocyte-monocyte progenitors, the immature cells that normally mature into macrophages, alive and multiplying in the laboratory while blocking their maturation. The expanded progenitors were then fitted with a chimeric antigen receptor targeting a marker on cancer cells.

In mice, the engineered progenitors behaved less like a dose than like an installed workshop: they settled in the bone marrow and went on producing further engineered immune cells. CAR-GMPs slowed disease in both blood cancers and solid tumours, and the effect was stronger when the cells also carried an extra immune activating signal meant to draw in and stimulate nearby immune cells, including T cells. In a mouse model of chronic granulomatous disease, the progenitors restored the animals' ability to fight bacterial infection. At Stanford, Ravi Majeti independently maintained and engineered the progenitors, confirming that the method could be reproduced.

Self renewal in the blood system was thought to belong mainly to hematopoietic stem cells, yet Ying said that under the right conditions GMPs can also self renew, offering a scalable starting point for cell therapies. The activating signal also worked when donor and recipient immune profiles did not match, which the authors suggest could allow off the shelf products prepared from donors in advance. The limits are plain: the cancer results are preclinical, with no human trials, no timeline and no quantitative outcomes reported, and safety and effectiveness in people remain to be established, particularly if the cells persist and keep producing immune cells over time.

granulocyte-monocyte progenitor

an immature blood cell, abbreviated GMP, that normally matures into macrophages and other immune cells

chimeric antigen receptor

a synthetic receptor, abbreviated CAR, engineered into a cell so that it recognises a chosen target

hematopoietic stem cell

a blood forming stem cell long regarded as the main self renewing cell of the blood system

self renewal