Histocompatibility: Edited by J. Michael Cecka and Elaine F. ReedDefining unacceptable HLA antigensZachary, Andrea Aa; Montgomery, Robert Ab; Leffell, Mary SaAuthor Information aDepartment of Medicine, USA bDepartment of Surgery, The Johns Hopkins School of Medicine, Baltimore, Maryland, USA Correspondence to Andrea A. Zachary, PhD, D. ABHI, Professor of Medicine, Director, Immunogenetics Laboratory, Johns Hopkins University School of Medicine, 2041 E. Monument Street, Baltimore, MD 21205, USA Tel: +1 410 614 8978; fax: +1 410 955 0431; e-mail: [email protected] Current Opinion in Organ Transplantation: August 2008 - Volume 13 - Issue 4 - p 405-410 doi: 10.1097/MOT.0b013e3283071450 Buy Metrics Abstract Purpose of review Neither the concept nor the formal application of unacceptable antigens is new. However, identification of unacceptable antigens is now sufficiently accurate to be used as a virtual crossmatch, which can both prevent the unnecessary shipment of organs and increase the access for sensitized patients. Recent findings Desensitization protocols and an increasing array of cell-depleting agents can overcome the immunological barriers to transplantation for some patients, reducing the risk of graft rejection to an acceptable level. Increasingly sensitive and specific assays for identifying HLA antigens and antibodies are providing more accurate definition of incompatibilities. Additionally, tests of various biomarkers may permit characterization of responder types. Summary The definition of unacceptable antigens is determined by the clinical protocols and the physiological and immunological characteristics of the recipient and donor. These data should be integrated to maximize the opportunity for transplantation. The development of additional tests to assess a patient's capacity for recognizing and responding to a transplant will improve the identification of incompatible donor–recipient pairs. Copyright © 2008 Wolters Kluwer Health, Inc. All rights reserved.