ORIGINAL ARTICLE Chemokine and chemokine receptor expression analysis in target organs of acute graft-versus-host disease A Bouazzaoui 1 , E Spacenko 1 , G Mueller 1 , S Miklos 1 , E Huber 2 , E Holler 1 , R Andreesen 1 and GC Hildebrandt 1 1 Department of Hematology and Oncology, University of Regensburg Medical School, Regensburg, Germany and 2 Department of Pathology, University of Regensburg Medical School, Regensburg, Germany Acute graft-versus-host disease (aGVHD) is a major complication after allogeneic bone marrow transplantation (allo-BMT), and infiltration of donor leukocytes into aGVHD target organs is partially orchestrated by chemokines. Using a murine BMT model, the expression of 30 chemokines or chemokine receptors in the lung, liver, gut and tongue was analyzed using real-time PCR at 1, 2, 3 and 6 weeks after BMT during the development of clinical aGVHD and target organ histopathology. CXCL9–11 expression was linked to elevated expression of CXCR3 in the gut, lung and tongue. In contrast, hepatic CXCR3 expression was not changed, whereas a clear association was seen for CXCL16 and CXCR6 expression. An elevated intestinal CCL3 expression 1 week after allo-BMT was associated with an increased expression of CCR5 but not CCR1 or CCR3, and in the lung and liver CCL3–CCL5 expression was associated with increases in CCR1 and CCR5. Overexpression of CCL2, CCL8, CCL12 and their receptor CCR2 was found in the liver and lung, but not in the gut and tongue. On the basis of the differences in kinetics and organ distribution, more studies are required to better characterize specific targets within this network, as this will allow the development of novel preventive and therapeutic approaches by using single or multiple targeting reagents. Genes and Immunity advance online publication, 2 July 2009; doi:10.1038/gene.2009.49 Keywords: stem cell transplantation; graft-versus-host disease; chemokine; chemokine receptor; leukocyte recruitment Introduction Allogeneic bone marrow transplantation (allo-BMT) often presents the only curative treatment for a number of malignant and non-malignant diseases. 1 However, its utility is limited by the development of severe treatment- related complications, most importantly, the occurrence of acute graft-versus-host disease (aGVHD). The patho- physiology of aGVHD is complex and can be divided into three phases as follows: (1) conditioning toxicity to host tissue, leading to the secretion of inflammatory cytokines and enhanced allo-stimulatory capacity of host antigen-presenting cells (APCs); (2) induction of donor T-cell activation and T-cell expansion; and (3) cellular effector phase, during which activated T cells are recruited into target organs and cause severe tissue injury. 2 Chemokines comprise a family of proteins predomi- nantly between 8 to 14 kDa, which at this point can be divided into four different subgroups: CC group (CCL1– 28), CXC group (CXCL1–16), C group (XCL1–2) and CX3C group (CX3CL1). 3,4 They exert their effects through the interaction with one or more members of a family of seven-transmembrane domain-containing G protein- coupled receptors. 5,6 Chemokine expression can be enhanced by inflammatory cytokines, 7 and chemokines have an important role in recruiting cells of the innate and adaptive immune system to the sites of inflamma- tion. 8–10 Furthermore, they can have additional functions in the context of leukocyte activation, 11 angiogenesis, 12,13 hematopoiesis 14 and organization or function of second- ary lymphoid tissues. 15–17 The chemokine-chemokine receptor system shows high complexity and redundancy with more than one chemokine binding to one receptor and multiple receptors interacting with one chemokine. Increased expression of a number of chemokines and chemokine receptors in GVHD target organs has been described earlier, 18–21 and previous studies have further shown that targeting one specific chemokine or chemo- kine receptor can result in the reduction of aGVHD- related injury to various target organs. 11,22–32 Interest- ingly, tropism and efficacy of such a strategy differed depending on the chemokine and/or the chemokine receptor involved, 33 suggesting that the enhanced ex- pression of chemokines after allo-BMT may differ between organs with respect to quality, quantity and kinetics. In this study, we analyzed chemokine and chemokine receptor expression patterns in GVHD target organs using a well-established murine BMT model, in which alloreactivity occurs across MHC (major histocompat- ibility complex) class I, MHC class II and minor Received 26 February 2009; revised and accepted 28 May 2009 Correspondence: Dr GC Hildebrandt, Department of Hematology and Oncology, University of Regensburg Medical Center, Franz- Josef-Strau Allee 11, Regensburg D-93053, Germany. E-mail: gerhard.hildebrandt@klinik.uni-regensburg.de Genes and Immunity (2009), 1–15 & 2009 Macmillan Publishers Limited All rights reserved 1466-4879/09 $32.00 www.nature.com/gene