CLINICAL TRANSPLANTATION Results from a Human Renal Allograft Tolerance Trial Evaluating T-Cell Depletion with Alemtuzumab Combined with Deoxyspergualin Allan D. Kirk, 1,4 Roslyn B. Mannon, 1 David E. Kleiner, 2 John S. Swanson, 3 Robert L. Kampen, 1 Linda K. Cendales, 1 Eric A. Elster, 1 Terri Wakefield, 1 Christine Chamberlain, 1 Steven C. Hoffmann, 1 and Douglas A. Hale 1 Background. Perioperative lymphocyte depletion induces allograft tolerance in some animal models, but in humans has only been shown to reduce immunosuppressive requirements. Without maintenance immunosuppression, de- pleted human renal allograft recipients experience rejection characterized by infiltration of the allograft with monocytes and macrophages. T-cell depletion combined with a brief course of deoxyspergualin (DSG), a drug with inhibitory effects on monocytes and macrophages, induces tolerance in nonhuman primates. We therefore performed a trial to determine if lymphocyte depletion with alemtuzumab combined with DSG would induce tolerance in humans. Methods. Five recipients of live donor kidneys were treated perioperatively with alemtuzumab and DSG and followed postoperatively without maintenance immunosuppression. Patients were evaluated clinically, by flow cytometry, and by protocol biopsies analyzed immunohistochemically and with real-time polymerase chain reaction. Results were compared to previously studied patients receiving alemtuzumab alone or standard immunosuppression. Results. Despite profound T-cell depletion and therapeutic DSG dosing, all alemtuzumab/DSG patients developed reversible rejection that was similar in timing, histology, and transcriptional profile to that seen in patients treated with alemtuzumab alone. Chemokine expression was marked prior to and during rejections. Conclusions. We conclude that treatment with alemtuzumab and DSG does not induce tolerance in humans. Chemo- kine production may not be adequately suppressed using this approach. Keywords: Alemtuzumab, Deoxyspergualin, Immunosuppression, Rejection, Tolerance, Transplantation. (Transplantation 2005;80: 1051–1059) T -cell depletion induces tolerance to allografted organs in some rodent (1, 2), canine (3), and nonhuman primate (NHP) (4, 5) models. Depletional induction has also been increasingly used clinically to reduce the need for posttrans- plant maintenance immunosuppression (6 –11). In particu- lar, alemtuzumab, a CD52-specific monoclonal antibody, has been shown to induce profound peripheral and central T-cell depletion in humans and to lessen the requirements for main- tenance immunosuppression following renal transplantation (6, 7, 9). Given the relatively low doses of maintenance immu- nosuppression that are apparently sufficient to prevent rejec- tion following alemtuzumab induction, we recently per- formed a trial to determine if patients could avoid additional antirejection medication completely with this aggressive depletional strategy (12). We showed that despite exception- ally low peripheral T-cell counts and nodal T-cell depletion, all alemtuzumab-treated patients in this our pilot study expe- rienced acute rejection unless some chronic immunosup- pressive therapy was used. These lymphopenic rejections were notable for prominent graft infiltration with monocytes and macrophages that coincided in all cases with peripheral monocyte repopulation during the third to fourth week after transplantation. This led us to hypothesize that monocytes were underimmunosuppressed by T-cell depletion alone and thus available as alternative effector cells for T-cell depletion- resistant rejection. Recent studies by Thomas et al. have shown that the addition of deoxyspergualin (DSG) to T-cell depletion with T-cell immunotoxin induces durable tolerance to renal allo- 1 Transplantation Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD. 2 Laboratory of Pathology, National Cancer Institute, National Institutes of Health, Bethesda, MD. 3 Organ Transplant Service, Walter Reed Army Medical Center, Washington, DC. 4 Address correspondence to: Allan D. Kirk, M.D., Ph.D., Room 5-5752, Building 10, Center Drive, Bethesda, MD 20892. E-mail: allank@intra.niddk.nih.gov. This trial was funded through intramural resources of the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, and by the Department of Army (SJS). Deoxyspergualin was supplied Nippon Kayaku America, Inc. (White Plains, NY). Received 29 April 2005. Revision requested 13 May 2005. Accepted 31 May 2005. Copyright © 2005 by Lippincott Williams & Wilkins ISSN 0041-1337/05/8008-1051 DOI: 10.1097/01.tp.0000174341.49741.8f Transplantation • Volume 80, Number 8, October 27, 2005 1051