Expression of the T-cell activation antigen, OX-40, identifies alloreactive T cells in acute graft-versus-host disease

Abstract

The OX-40 molecule is expressed on the surface of recently activated T lymphocytes. The presence of OX-40 on CD4+ T cells was analyzed in a rat haplo-identical (parental → F1) bone marrow transplant model of acute graft- versus-host disease (aGVHD). Increased numbers of activated CD4+ T cells that expressed the OX-40 antigen were detected in peripheral blood soon after transplantation before the earliest sign of disease. The peak of OX-40 expression occurred 12 days posttransplantation with a range of 18% to 36% of circulating T cells and remained 10-fold above background, never returning to baseline. A slight increase in OX-40 expression (range, 1% to 6%) was also detected on peripheral blood lymphocytes from control syngeneic F1 → F1 recipients. OX-40+ T cells were isolated from spleen, skin, lymph node, and liver tissue of rats undergoing aGVHD, but not in syngeneic transplants. OX- 40+ T cells isolated from these tissues were of donor origin and were shown to be alloreactive. These data raise the possibility of using the OX-40 antibody to detect and deplete selectively the T cells that cause aGVHD.