CLINICAL TRANSPLANTATION Heterogeneous Alterations in Human Alloimmunity Associated with Immunization Meagan Roddy, 1 Michael Clemente, 1 Emilio D. Poggio, 1 Ronald Bukowski, 2 Snehal Thakkar, 2 Gunter Waxenecker, 3 Hans Loibner, 3 Gottfried Himmler, 3 Donald E. Hricik, 4 and Peter S. Heeger 1,5,6 Background. The presence of alloantibodies and/or alloreactive T cells in a patient prior to a transplant can impact graft outcome. Environmental factors, including therapeutic vaccinations, may influence the strength and/or specificity of alloimmunity. Methods. To address this issue, we prospectively evaluated the effects of two different immunization protocols in human subjects on cellular alloimmunity using an IFN ELISPOT assay and on alloantibody reactivity by flow cyto- metric analysis of HLA-coated beads. Results. Vaccination/immunization was associated with augmentation of cellular and/or humoral alloimmune reac- tivity in 50% of the test subjects. The effects were heterogeneous in that some detected increases were transient, peaking 30-60 days postimmunization, whereas others persisted for the length of the study. Antibodies reactive to the immunizing agent did not cross react with the detected alloantibodies, suggesting that the augmentation of alloimmune reactivity was most likely due to a nonspecific adjuvant effect from the vaccine. Conclusions. Therapeutic vaccinations can alter the strength of cellular and humoral alloimmunity in humans. The results suggest that serial immune monitoring of alloreactivity might be beneficial when immunizations are adminis- tered to potential transplant recipients. Keywords: T lymphocyte, Cytokine, Alloreactivity, Immunization. (Transplantation 2005;80: 297–302) A lloreactive T cells and alloantibodies are known media- tors of acute and chronic allograft injury, processes that limit the lifespan of transplanted organs (1–4). The presence of pretransplant anti-HLA antibodies in a potential recipient, as detected by a positive panel of reactive antibody (PRA) test and/or a positive crossmatch test, are known to increase the risk for early posttransplant injury/graft loss (1,5); transplan- tation is generally not performed across a positive cross- match. As the sensitivity of alloantibody testing has improved through the use of flow cytometric bead techniques, it has also become clear that low titers of antidonor HLA antibody not detected in standard crossmatch studies (that do not pre- clude transplantation) may also predict a poor posttransplant prognosis (6–9). Studies from our laboratory have shown that antidonor effector/memory T cells can be detected in the peripheral blood of transplant recipients prior to and following trans- plantation (10 –13). The emerging data suggest that the fre- quency of pre- and posttransplant antidonor T cell immunity positively correlates with poor posttransplant outcome, po- tentially because such effector/memory T cells are resistant to standard immunosuppression regimens (10,14). The specificity and or strength of alloimmune reactivity may vary over time, particularly in response to environmen- tal stimuli. PRA values, for example, can change significantly while patients await transplantation (15–17). Because the strength of the alloimmune repertoire prior to transplanta- tion impacts on posttransplant outcome, understanding ex- ogenous factors that influence antidonor immunity prior to transplantation has important clinical implications. Organ transplantation requires recipient immunosup- pression and thereby carries inherent infectious risks. Physi- cians commonly administer vaccinations against infectious pathogens (i.e. influenza, hepatitis B) in these patients to in- duce/augment protective immunity. Although such a prac- tice may be efficacious, it is possible that the immunization procedure, as a “nonspecific” proinflammatory stimulus and/or via priming of cross-reactive T or B cells, could en- This study was supported in part by a grant from the Igeneon Corporation, National Institutes of Health contract N01-AI-05410, and the Leonard Rosenberg Fund. 1 Department of Immunology, The Cleveland Clinic Foundation, Cleveland, OH. 2 Taussig Cancer Center, The Cleveland Clinic Foundation, Cleveland, OH. 3 Igeneon Corporation, Vienna, Austria. 4 Department of Medicine, Case Western Reserve University, Cleveland, OH. 5 The Institute of Pathology, Case Western Reserve University, Cleveland, OH. 6 Address correspondence to: Peter S. Heeger, M.D., Department of Immu- nology, The Cleveland Clinic Foundation, NB30, 9500 Euclid Ave., Cleveland OH 44195. E-mail: heegerp@ccf.org. Received 10 January 2005. Revision requested 25 January 2005. Accepted 18 February 2005. Copyright © 2005 by Lippincott Williams & Wilkins ISSN 0041-1337/05/8003-297 DOI: 10.1097/01.tp.0000168148.56669.61 Transplantation • Volume 80, Number 3, August 15, 2005 297