Serum interleukin-6 levels during bone marrow transplantation: impact on transplant-related toxicity and engraftment.

The biological properties of IL-6 include the induction of acute phase proteins, stimulation of hematopoietic stem cell growth and thrombopoiesis. Serum levels of IL-6 were closely monitored in 66 patients before and after allogeneic (n = 37), autologous bone marrow transplantation (n = 8) or autologous peripheral blood stem cell transplantation (n = 21). Almost every patient showed elevated IL-6 serum levels during the aplastic phase. Patients then suffered from mucositis, had elevated C-reactive protein (CRP) and usually body temperatures of above 38 degrees C. It was investigated whether IL-6 serum levels, apart from inducing acute phase reactions, correlated with transplant-related complications or leukocyte and thrombocyte engraftment. By statistical analysis, a correlation was found between IL-6 and CRP and between IL-6 and fever. In contrast, no correlation was found between IL-6 and elevated serum bilirubin as a marker for hepatotoxicity. IL-6 showed a weak negative correlation with leukocyte or platelet counts. In contrast, the day of platelet engraftment correlated with the day of peak serum IL-6 value, possibly indicating an influence of IL-6 on platelet engraftment.