A high percentage of HLA-DQ+ and HLA-DR+ mononuclear cells is associated with a low incidence of acute graft-versus-host disease after allogeneic bone marrow transplantation (BMT) in children.

In order to discover some biological markers of acute graft-versus-host disease (aGVHD), we have studied the percentage of peripheral monocytes and T lymphocytes bearing HLA-DR and HLA-DQ class II molecules. This study included 25 allogeneic BMT in children, either with (n = 10) or without (n = 15) aGVHD. Within 2 months after transplantation, a higher percentage of DQ+ and DR+ monocytes and of DQ+ T lymphocytes was observed in patients without aGVHD compared with patients with aGVHD. The most discriminating marker was the strong increase in the percentage of DQ+ monocytes in patients without aGVHD (P = 0.001). In a sequential study, we observed a low percentage of DQ+ and DR+ peripheral blood mononuclear cells (PBMC) as long as the clinical manifestations of aGVHD continued. We speculate if the modulation of DQ and DR molecules on PBMC after BMT is a consequence of the action of some lymphokines, and if it plays a role in the regulation of the acute GVH reaction. We conclude that MHC class II molecules on peripheral mononuclear cells may be reliable biological markers for the diagnosis of aGVHD.