Preventing graft re-JAK-tion: safer transplant conditioning enables murine islet allograft tolerance and diabetes reversal.

Transplantation of allogeneic islets of Langerhans, which include the insulin-producing β cells of the endocrine pancreas, holds curative potential for type 1 diabetes (T1D). However, protecting the allograft from the host immune system has long been a challenge impeding wider use of this therapy. Inducing mixed hematopoietic chimerism via allogeneic hematopoietic stem cell transplantation (HSCT) can achieve long-lasting donor-specific immune tolerance, but the toxicities of conventional HSCT conditioning agents limit the use of this approach. In this issue of the JCI, Bhagchandani et al. have used the JAK1/2 inhibitor baricitinib to optimize a nonmyeloablative antibody-based HSCT conditioning regimen, achieving multilineage hematopoietic engraftment, which enabled curative islet allotransplantation in a mouse model of T1D.