Chemokine Receptor CCR5 Mediates AlloImmune Responses in Graft-versus-Host Disease

Allogeneic bone marrow transplantation (BMT) is an effective therapy for hematologic malignancies. However graft-versus-host disease (GVHD) is a major limiting factor for a successful patient outcome. GVHD is a result of alloimmune responses of donor T lymphocytes attacking the recipient's cells and tissues. Chemokine receptor CCR5 plays a role in solid organ allograft rejection and mediates murine GVHD pathogenesis. Herein, we report that infiltrating lymphocytes in the skin of human acute GVHD (aGVHD) samples are predominantly CCR5⁺ T cells. In addition, we characterized the features of the CCR5 expression on alloreactive T lymphocytes. We found that the CCR5⁺ population exhibits the characteristics of the activated effector T cell phenotype. CCR5 expression is upregulated upon allogenic stimulation, and CCR5⁺ cells are proliferating with coexpression of T cell activation markers. Furthermore, the activated T cells producing inflammatory cytokine tumor necrosis factor (TNF)α, interleukin (IL)-2, or interferon (IFN)-γ, are positive for CCR5. Thus, CCR5 is a marker for GVHD effector cells and CCR5⁺ T cells are active participants in the pathogenesis of human aGVHD.