IntroductionAcute graft-versus-host disease (aGvHD) is one of the major complications after allogeneic bone marrow transplantation (BMT), which limits the success of this otherwise life-saving strategy. 1 Our group and others have demonstrated that naturally occurring CD4 ϩ CD25 ϩ regulatory T cells (Treg cells) can reduce the incidence and severity of murine aGvHD. [2][3][4][5] In spite of findings that cell-cell contact is critical for Treg-mediated suppression in vitro and that IL-10 production 6 and TGF- surface expression 7 are relevant in vivo, the mechanisms by which Treg cells exert suppressor activity in the setting of aGvHD are poorly understood. Recent reports have described the role of apoptosis induction by activated Treg cells of conventional T cells (Tconv cells) and B cells as a mechanism of suppression. [8][9][10][11][12] The TNF-R superfamily member CD30 has been shown to be expressed on Tr1 regulatory cells that down-modulate nickelspecific immune responses 13 and to be relevant for Treg-mediated protection from allograft rejection. 9 In human immune-mediated diseases, CD30 is expressed on T cells that serve a regulatory role in rheumatoid arthritis 14 and on cells that accumulate at the inflammatory sites of patients with systemic sclerosis 15,16 and chronic GvHD. 15 Expression of CD30 is detected late after T-cell activation in vitro with immobilized CD3 mAb 17 and activationinduced CD30 is found on T helper 1 (Th1), Th0, and Th2 cell clones. 18,19 CD30 signaling up-regulates the lymph node homing molecule CCR7, 20 provides costimulatory signals to T cells, and enhances their proliferative responses to suboptimal stimulation via T-cell receptor (TCR) engagement. 17,21 The ligand for CD30 (CD30L, or CD153) is a membraneassociated glycoprotein related to TNF, 21 which is known to be expressed on thymic epithelial cells (TECs), antigen presenting cells (APCs), activated T cells, neutrophils, eosinophils, and resting B cells. 22,23 CD30-deficient C57B/6 mice display elevated numbers of thymocytes and a gross defect in negative selection, 24 although this was not found in all mouse strains. 25 Overexpression of CD30 on T cells results in augmented thymocyte depletion upon treatment with a superantigen, 26 suggesting an important role for CD30/CD153 interactions in thymic deletion of autoreactive T cells. Recently, the thymic medulla has been demonstrated to be an anatomic site where Treg cells interact with activated dendritic cells (DCs) and Hassall corpuscles 27 that express CD153. 23 In this report, we investigated the role of CD30 signaling in Treg-cell function, demonstrating a critical role for CD30/CD153 interactions early after adoptive transfer.
Materials and methods
MiceFVB/N (H-2k q , Thy-1.1), C57B/6 (H-2k b , Thy-1.1 or Thy-1.2), C57B/ 6 eGFPϩ , and Balb/c (H-2k d , Thy-1.2) mice were purchased from Jackson Laboratory (Bar Harbor, ME) or Charles River Laboratory (Wilmington, MA). CD30-deficient C57B/6 mice were kindly provided by Dr T. Mak (University of Toronto, ON, Canada); Balb/c...