Human leukocyte antigen DR surface expression on CD14+ monocytes during adverse events after hematopoietic stem cell transplantation

The human leukocyte antigen DR surface expression on CD14+ monocytes reflects the degree to which these cells have been activated. Given the central role monocytes and macrophages play in the immune system, a decreased human leukocyte antigen DR expression on CD14+ monocytes results in a hallmark of altered immune status during systemic inflammatory response syndrome. We hypothesize that human leukocyte antigen DR expression might be similarly altered after hematopoietic stem cell transplantation and during post-transplant complications. Using flow cytometry, this study investigates the human leukocyte antigen DR surface expression of CD14+ monocytes in 30 pediatric and young adult patients up to 1 year after hematopoietic stem cell transplantation. Normal values were derived from a control group of healthy children, adolescents, and young adults. Human leukocyte antigen DR expression decreased significantly prior and during bacterial infection or sepsis. By contrast, human leukocyte antigen DR expression levels were elevated before and at the time of viremia. Human leukocyte antigen DR expression was also elevated during acute graft-versus-host disease. In contrast, the expression was reduced when patients had hepatic veno-occlusive disease. A significant decrease of human leukocyte antigen DR expression was associated with a relapse of the underlying disease and before death. Human leukocyte antigen DR expression on CD14+ monocytes appears to be a promising parameter that might allow identification of patients at risk after hematopoietic stem cell transplantation.