A trick from cancer cells helps rats accept transplanted limbs
To help rats adopt transplanted limbs as their own, researchers have harnessed a ruse that cancer cells use to hide from the immune system — effectively reprograming the animals’ defenses to ignore foreign tissue. Rats injected with engineered microparticles tolerated a hind limb transplant from another rat for more than 200 days, even in the absence of drugs that suppress immune responses, researchers report March 13 in Science Advances. When injected into the transplanted tissue, the microparticles release a signaling protein known as CCL22 that’s secreted from cancer cells and attracts specialized immune cells. These immune cells, called regulatory T cells, can mark the rat’s new tissue as “self” and protect it from an onslaught of immune defenses that would normally attack foreign material. The microparticle treatment is “fundamentally different than anything that is used right now in clinical medicine simply because it doesn’t suppress the animal’s immune system,” says James Fisher, a bioengineer at the University of Pittsburgh. Patients who receive donor organs or tissues typically spend the rest...