High-risk corneal allografts and why they lose their immune privilegeNiederkorn, Jerry YCurrent Opinion in Allergy and Clinical Immunology: October 2010 - Volume 10 - Issue 5 - p 493–497 doi: 10.1097/ACI.0b013e32833dfa11 Eye allergy: Edited by Leonard Bielory and Stefano Bonini Buy Abstract Author InformationAuthors Article MetricsMetrics Purpose of review Corneal allografts are routinely performed without HLA typing or systemic immunosuppressive drugs. However, certain conditions create high risks for immune rejection. This review discusses recent insights into the mechanisms that rob the corneal allograft of its immune privilege. Recent findings Studies in mice have revealed that stimuli that induce new blood vessel growth in the cornea also elicit proliferation of lymph vessels. Lymph vessels facilitate migration of antigen-presenting cells to regional lymph nodes in which they induce alloimmune responses. The presence of blood vessels in the corneal graft bed creates a unique chemokine milieu that stimulates recruitment of sensitized lymphocytes into the corneal allograft. Other data indicate that although corneal allograft survival is closely associated with Foxp3 expression in CD4+CD25+Foxp3+ T regulatory cells (Tregs), reduced expression of Foxp3 in Tregs creates a high risk for graft rejection. Recent evidence indicates that allergic diseases have a profound impact on the immune response and produce a dramatic increase in corneal allograft rejection. Summary Understanding the underlying mechanisms that create ‘high-risk’ hosts may provide important therapeutic targets for restoring immune privilege of corneal allografts and enhancing their survival. Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA Correspondence to Dr Jerry Y. Niederkorn, PhD, Department of Ophthalmology, 5323 Harry Hines Blvd, Dallas, TX 75390, USA E-mail: firstname.lastname@example.org Copyright © 2010 Wolters Kluwer Health, Inc. All rights reserved.