Correspondence: Bipin N. Savani, MD, Hematology and Stem Cell Transplantation Section, Vanderbilt University Medical Center, 2655 The Vanderbilt Clinic, Nashville, TN 37232–5505, USA. E-mail: Bipin.Savani@Vanderbilt.Edu (Received 6 March 2010; accepted 17 May 2010) SHORT COMMUNICATION Early lymphocyte reconstitution is associated with improved transplant outcome after cord blood transplantation SARA K. TEDESCHI, MADAN JAGASIA, BRIAN G. ENGELHARDT, JENNIFER DOMM, ADETOLA A. KASSIM, WICHAI CHINRATANALAB, SUSAN LEIGH GREENHUT , STACEY GOODMAN, JOHN P. GREER, FRIEDRICH SCHUENING, HAYDAR FRANGOUL & BIPIN N. SAVANI Hematology and Stem Cell Transplantation Section, Division of Hematology/Oncology, Department of Medicine, Vanderbilt University Medical Center and Veterans Affairs Medical Center, Nashville, Tennessee, USA Abstract Background aims. Previous studies have shown that rapid recovery of the absolute lymphocyte count (ALC) is associated with improved transplant outcomes after related and unrelated donor allogeneic stem cell transplantation (allo-SCT). No consistent association has been reported between lymphocyte recovery and transplant outcome after cord blood transplan- tation (CBT). Methods. We reviewed the records of 40 consecutive CBT patients at our institution to determine the impact of lymphocyte recovery on transplant outcome. Results. The majority of patients (83%) received CBT for hematologic malignancies. Patients with ALC 150/ μL at 30 days post-CBT had decreased non-relapse mortality (NRM) ( P = 0.011) and improved survival ( P = 0.013) compared with ALC 150/ μL. Patients with ALC 100/ μL at 30 days post-CBT had a significantly higher rate of graft failure than those with ALC 100/ μL (four of 10 versus one of 29; P = 0.011). ALC was positively correlated with the nucleated cell dose and inversely correlated with the patient’ s age. There was no relation- ship between disease risk, type of conditioning regimen, anti-thymocyte globulin and number of cord units on ALC recov- ery. Conclusions. Our results indicate that ALC 30 days post-CBT is a surrogate for engraftment, and that low ALC ( 150/ μL) identifies an ‘at-risk’ population of patients after CBT. Studies are needed to determine ways to increase ALC cell numbers post-CBT, including ex vivo-expanded natural killer cells using adoptive immunotherapy, which might improve outcome after CBT. Key Words: cord blood, lymphocyte recovery , non-relapse mortality , survival, transplantation Introduction In October 1988, the world’ s first cord blood transplan- tation (CBT) was performed. Umbilical cord blood (CB) has now become one of the most commonly used source of hematopoietic cells for allogeneic stem cell transplantation (allo-SCT) (1). Today more than half of allo-SCT are performed using grafts from unrelated sources, either unrelated donor or CB units. It is esti- mated that 600 000 CB units have been banked and more than 20 000 CBT have been performed world- wide for adults and children with life-threatening malignant and non-malignant diseases (1). Rapid recovery of the absolute lymphocyte count (ALC) has been reported to be associated with improved transplant outcomes after related- and unrelated-donor allo-SCT (2–4). Natural killer (NK) cells, which mediate cytotoxicity without prior sensi- tization, are the first lymphocytes to recover after allo- SCT and comprise the majority of peripheral blood lymphocytes after transplantation (5–7). Rapid recov- ery of NK cells at 1 month post-allo-SCT has been associated with rapid neutrophil and platelet engraft- ment and decreased non-relapse mortality (NRM) (8). Studies have shown that prolonged T-cell lym- phopenia and compensatory expansion of B and NK cells occur early after CBT. However, no consistent association has been reported between lymphocyte/ NK cell recovery and transplant outcome after CBT. Cytotherapy, 2011; 13: 78–82 ISSN 1465-3249 print/ISSN 1477-2566 online © 2010 Informa Healthcare DOI: 10.3109/14653249.2010.495114