Granulocyte-macrophage colony-stimulating factor in the sera of patients with aplastic anemia.

To clarify the role of growth factors in the pathophysiology of aplastic anemia we measured serum granulocyte-macrophage colony-stimulating factor (GM-CSF) levels in 33 aplastic anemia patients by a specific and sensitive enzyme-linked immunosorbent assay. GM-CSF serum levels of patients with aplastic anemia were significantly higher than in healthy volunteers. GM-CSF levels were correlated with the severity of aplastic anemia but not with the absolute neutrophil count. Since T lymphocytes are one of the main sources of GM-CSF, our data provide further evidence for in vivo T lymphocyte activation in aplastic anemia. GM-CSF serum levels are higher in patients responding to immunosuppressive treatment than in nonresponders. Elevated serum GM-CSF might be predictive of a good response to immuno-suppressive therapy. GM-CSF serum levels are lower immediately after treatment with antilymphocyte globulin/antithymocyte globulin (ALG/ATG) than corresponding pretreatment values. Thus we cannot confirm the hypothesis that ALG/ATG effects in vivo are mediated by stimulating the release of growth factors. We conclude that in aplastic anemia the primary defect is a failure in GM-CSF response rather than in GM-CSF supply.