Optimised use of immunosuppression and biological therapies can provide satisfactory disease control to a significant proportion of patients with inflammatory bowel disease (IBD). However, these treatments are never curative and may contribute substantially to long-term morbidity. In severely affected patients, the personal and societal costs of IBD and their treatments are very high, and lack of efficacy continues to result in progressive organ damage, a need for surgery, and chronic disability.

Cellular therapy with stem cells and their progeny is a promising new approach capable of addressing yet unmet medical needs in various inflammatory and autoimmune diseases. The considerable excitement surrounding the stem cell field was initially based on the unique biological properties of these cells and their capacity to self-renew and regenerate tissue and organ systems; later, the immunomodulatory ability of stem cell therapy has become also apparent. A prevailing view is that two types of stem cells coexist in the bone marrow: haematopoietic stem cells (HSCs) and stromal, or mesenchymal stem cells (MSCs).1The ontogenic relationship between HSCs and MSCs remains unclear.

The concept and practice of stem cell transplantation began with HSCs, and was originally supported by decades of animal experiments and by the serendipitous remissions of inflammatory diseases observed in patients undergoing transplantation for haematological disorders. Basic science and animal experiments continue to play an important role in our understanding of the mechanisms involved. Data form animal studies of HSC transplant (HSCT) in autoimmune diseases show that allogenic HSCT may prevent and cure autoimmune disease, and unexpectedly, durable remissions may also be achieved following autologous HSCT. Terms such as “resetting the immunostat” and “debulking of inflammatory load” are being used without supporting evidence despite the opportunities of a highly developed array of techniques for studying immune reconstitution post-transplant. Initially, a beneficial effect is likely to …