Crohn's disease is an 'auto-immune' disorder of the gut. In this condition the body's own immune system is fighting its gut and causing inflammation and other symptoms. Patients who are refractory (not responding) to the medications usually used to control Crohn's disease (medicines like steroids, azathioprine, methotrexate, cyclophosphamide and antibodies like Infliximab), may consider being part of this study.||In this study, the investigators plan to wipe out (ablate) the 'faulty immune system' with medicines (immune-ablation) and then give back the patients own stored stem cells (that have been collected before) - a procedure called autologous (self) stem cell transplant (ASCT). Once the new immune system regrows again from the stem cells, it is hoped that the 'faulty' immune cells do not return again and do not fight the gut leading to remission from symptoms of Crohn's disease. The aim of this treatment therefore, is to reset or re-program the immune system, so that it does not fight the patient's own body.||Currently, there are very few trials and experience with this procedure in children and young adults. There have been a few studies that have shown benefit of ASCT procedure in adult patients. In some patients, the benefit lasted for 1-5 years; but 1 in 5 (20%) participants were not taking their medications for the Crohn's disease even 5 years after ASCT. Other 80% needed medications again, but in most cases with better disease control.||In order to potentially improve the long term outcomes of ASCT, the investigators are adding another medication (in addition to those used in adult studies) called IL-2 (Aldesleukin), which will be given as an every-other-day injection under the skin (subcutaneous) at very low doses for 6 weeks after the ASCT and can be taken at home. Low dose IL-2 is known to increase a type of immune cell called T-regulatory cells (Tregs) that make immune cells less reactive to self. Study doctors believe that increased population of Tregs after ASCT may lead to a better control of Crohn's disease- higher percentage of cures or disease control for a longer period of time compared to the previous adult trials.||Therefore, the goals of this study are-||To see if ASCT can be used safely and can provide substantial benefit in young adults who have refractory Crohn's disease.|To see if addition of IL-2 after the ASCT is safe and effective.