The human leukocyte antigen DR (HLA-DR) surface expression on CD14+ monocytes reflects the degree of activation of these cells. In line with the central role of monocytes and macrophages in the immune system, a decreased HLA DR expression on CD14+ monocytes has been shown to be a hallmark of an altered immune status during the systemic inflammatory response syndrome (SIRS). We therefore hypothesized that HLA-DR expression might likewise be altered after hematopoietic stem cell transplantation (HSCT).
HLA-DR surface expression of CD14+ monocytes was assessed by flow cytometry in 30 pediatric patients (below 15 years, n=23) and young adults (15 years and above, n=7) up to one year after HSCT (7 autologous and 23 allogeneic stem cell transplants). Normal values were derived from a control group of healthy children (n=18) and young adults (n=22).
During the conditioning period, a significant increased HLA-DR expression in pediatric patients and young adults was observed. This increase could not be attributed to the administration of anti-thymocyte globulin (ATG). After HSCT, HLA-DR expression was not altered in general. However, HLA-DR expression decreased significantly up to 5 days before (p<0.05) and during (p<0.01) bacterial infections or sepsis. In contrast, HLA-DR expression levels were increased 7–10 days before and at the time of diagnosis of viral infections. HLA-DR expression was also elevated during acute graft-versus-host disease (GVHD). At the time of hepatic veno-occlusive disease (VOD), HLA-DR expression on CD14+ monocytes was reduced. Neither the administration of granulocyte colony-stimulating factor (G-CSF) nor the occurrence of a relapse was associated with a change of HLA-DR expression.
In conclusion, adverse events after HSCT were associated with altered HLA-DR expression levels. Therefore, HLA-DR expression on CD14+ monocytes appears as a promising parameter which might allow identifying patients at risk after HSCT.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.