Regulatory T Cells Prevent Effector T Cell Infiltration Into GvHD Target Tissue by Affecting Chemokine Signaling

• Published in: Blood 2009-11, Vol.114 (22), p.1341-1341
• Main Authors: Turner, Brie, Ahmed, Shaheda, Pagan, Sarah, Norden, Jean, Collin, Matthew, Dickinson, Anne M, Wang, Xiao Nong
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V114.22.1341.1341

Abstract 1341 Poster Board I-363 Graft versus host disease (GVHD) following haematopoietic stem cell transplantation is often first observed in the skin; a primary target organ of GVHD. GVH related tissue damage in the skin is mainly driven by infiltrating alloreactive cytotoxic effector T cells, facilitated by a cascade of cytokines and chemokines. Our recently published observations showed that addition of regulatory T cells (Treg) suppressed skin GVH tissue damage mediated by alloreactive CD8+ T cells in an in vitro human GVHD skin explant model [1]. The current study investigated the role of Treg in modulating effector T cell infiltration into skin, it's consequence on the severity of skin GVH histopathology and the possible changes of effector T cell production and expression of chemokines and chemokine receptors. CD8+ T cells, monocyte derived dendritic cells (mDC) and natural Treg (CD4+CD2highFOXP3+) were generated as previously described [1]. In an in vitro human GVHD skin explant model, CD8+ T cells and ex vivo expanded Treg obtained from buffy coats were used as “donor” cells. mDC and skin biopsies obtained from HLA unmatched unrelated normal volunteers acted as “recipient” tissues. “Donor” CD8+ T cells primed with “recipient” mDC in the presence or absence of Treg were co-cultured with “recipient” skin. The severity of histopathological GVH skin damage was scored as grade 0 to grade IV using a clinically validated scoring system. The number of infiltrating CD8+ T cells in skin was evaluated using immunohistochemistry then correlated to the severity of skin GVH histopathology. The gene expression of selected chemokines and chemokine receptors in alloreactive CD8+ effector T cells was analysed using quantitative RT-PCR. The effector T cell expression of chemokine receptors was assessed using flow cytometry. The secretion of selected chemokines into the culture supernatants was quantified using BD cytometric bead array kit. The percentage of infiltrating effector T cells in skin was significantly associated with the severity of skin GVH histopathology (2.6±0.8, 12.6±3.1 and 27.2±2.7 for skin sections with GVH histopathology grade I, II and III-IV; p=0.017 and 0.021 respectively). The percentage of skin infiltrating CD8+ T cells was significantly reduced by the presence of Treg (24.8±3.7 vs 11.58±1.8, p=0.011, n=13) which correlated with Treg mediated suppression of skin GVH histopathology (p