Thymus Organoids Rebuild Immune Selection

Researchers tested whether an engineered thymus, the organ that trains immune cells, could restore immunity while teaching it to accept a transplant. In mice born without a thymus, implanted three-dimensional niches containing thymic epithelial cells, which select developing T cells, recruited host T-cell progenitors and produced diverse T cells. The new cells supported antibody refinement and rejected genetically mismatched skin grafts. The sharper test used epithelial cells displaying donor major histocompatibility complex, or MHC, molecules, identity signals recognized by T cells. Mice accepted skin from that donor yet rejected third-party grafts. The study shows functional immunity and donor-specific tolerance; exactly how selection was rebuilt remains inferred.