@article{discovery10050119, month = {October}, pages = {1152--1160}, journal = {Journal of Allergy and Clinical Immunology}, note = {This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions.}, publisher = {MOSBY-ELSEVIER}, volume = {138}, year = {2016}, title = {Effect of stem cell source on long-term chimerism and event-free survival in children with primary immunodeficiency disorders after fludarabine and melphalan conditioning regimen}, number = {4}, abstract = {BACKGROUND: Reduced-intensity conditioning (RIC) regimens are increasingly being used in the transplantation of patients with primary immunodeficiency disorders (PIDs), but there are no large studies looking at long-term lineage-specific chimerism. OBJECTIVES: We sought to analyze long-term chimerism and event-free survival in children undergoing transplantation for PIDs using RIC with fludarabine and melphalan (Flu/Melph) and to study the effect of donor type and stem cell source. METHODS: One hundred forty-two children underwent transplantation with RIC by using Flu/Melph and for PIDs by using bone marrow (n = 93) or peripheral blood stem cells (PBSCs; n = 49). Donors were matched unrelated donors (n = 72), mismatched unrelated donors (n = 37), matched sibling donors (n = 14), matched family donors (n = 12), and mismatched family donors (n = 7). RESULTS: Overall survival at a median follow-up of 7.5 years was 78\%, irrespective of stem cell source or donor type. When bone marrow was used as the stem cell source, 26\% of patients ended up with very low levels of donor chimerism ({\ensuremath{<}}10\% donor), especially in the myeloid lineage. Event-free survival in this group was significantly lower compared with that in the rest of the group (25\% vs 70\%, P {\ensuremath{<}} .001). With the use of PBSCs, more than 90\% of patients achieved complete donor chimerism or high-level mixed chimerism ({\ensuremath{>}}50\% donor chimerism) in all lineages. CONCLUSIONS: On the basis of our experience, we would suggest that PBSCs should be the stem cell source of choice in children with PIDs undergoing transplantation with Flu/Melph RIC from a matched donor source. This is most likely to ensure sustained high-level donor chimerism.}, author = {Rao, K and Adams, S and Qasim, W and Allwood, Z and Worth, A and Silva, J and Lucchini, G and Chiesa, R and Veys, P and Amrolia, P}, url = {https://doi.org/10.1016/j.jaci.2016.01.053}, issn = {1097-6825}, keywords = {PID, HSCT, chimerism, lineage specific, reduced intensity} }