I am a pediatric blood & marrow transplant physician. I have read the article abstract, but I don't subscribe to Science Translational Medicine, so I won't be able to read the article until my hospital library orders & acquires the article. These comments are based only on the abstract.
The Slashdot summary is misleading about what is novel in research. Unrelated donor bone marrow transplants (or hematopoietic stem cell transplants (HSCT), which are a superset) have been done routinely since the 1990's.
Allogeneic (meaning the stem cell source is another person, rather than the patient himself/herself) HSCT patients take immunosupressive medications to try to prevent (or to treat) graft versus host disease (GVHD). If the patient does not develop GVHD, they are usually weaned off the immunosuppressive medications by 6 months after transplant. Patients who do develop GVHD can require years (sometimes 5-10 years) of immunosuppression. In contrast, patients who receive common solid organ transplants (heart, liver, kidney) are usually on immunosuppressive medications for life, although the immunosuppression is typically stronger for the first few months after transplant. The article reports on patients who received simultaneous kidney and HSC transplants from the same donor. Some of these patients could be weaned off of immunosuppression. Although this type of simultaneous transplant is not common, it has been reported before, as well as the finding that patients could come off immunosuppression.
What is novel is the ability to perform unrelated donor transplants using donors who were not good HLA matches (the matching system that is used for HSCT) and not have the recipients develop GVHD. This was accomplished by manipulating the stem cell product after it had been collected from the donor, but before it was infused into the recipient. The majority of HSCT done today are done with unmanipulated stem cell products (I'm not counting processing that often needs to be done when the donor and recipient don't have the same red cell type - which is controlled by a different genetic system than HLA). However, some forms of stem cell product manipulation (T-cell negative selection and CD34+ cell positive selection) have been around for a few decades. They can be successfully used to decrease the risk of GVHD, but at the price of increasing the risk of graft rejection, relapse (for leukemias) and infection. In the end, almost all studies of those methods show that the overall survival or disease-free survival is unchanged.
This article describes a more sophisticated form of stem cell manipulation, in which the graft is enriched in hematopoietic stem cells and tolerogenic graft facilitating cells. There have been past reports of other sophisticated stem cell manipulations giving good results in a study, but these techniques require elaborate facilities to perform, and often when they have been replicated by groups other than the original group, the patient outcomes have not been as good as those in the original report.
So my bottom line is that this result is exciting, but needs at minimum validation in a multicenter study before it starts to look like a game changer.
To address some of the other comments:
1) The concern about graft-versus-leukemia effects is a valid one and it will need to be studied. However, that is not an issue when doing a transplant for a non-malignant disease, so it would be a definite win for those patients. For leukemias, the GVL effect is strongest in CML, then AML, and weakest in ALL (kids don't get CLL, so I don't know much about that disease). Ultimately it would take clinical trials to determine if the benefit from less GVHD outweighs increased relapse risk (if any) from decreased GVL.
2) The article uses reduced-intensity radiation / chemotherapy, which isn't exactly a picnic, but it is less toxic than standard-dose (10-14 Gy) total body irradiation and 120 mg/kg cyclophosphamide (or 4 day busulfan and 120-200 mg/kg cyclophosphamide).