Plasma lactoferrin content in neutropenic patients: effects of treatment with recombinant granulocyte-macrophage colony-stimulating factor.

Plasma lactoferrin content was measured before and after therapy with recombinant granulocyte-macrophage colony-stimulating factor in five patients with aplastic anaemia, six with myelodysplasia, and three with prolonged, severe, chemotherapy-induced neutropenia. Before therapy plasma lactoferrin content was uniformly low. However, patients with aplastic anemia and those with chemotherapy-induced neutropenia had a normal lactoferrin:neutrophil ratio. The low levels of plasma lactoferrin thus reflected the low granulocyte mass. On the other hand, patients with myelodysplasia also had reduced lactoferrin:neutrophil ratios, suggesting qualitative/quantitative abnormalities of neutrophil lactoferrin production. After treatment with granulocyte-macrophage colony-stimulating factor, plasma lactoferrin levels increased in patients with aplastic anemia and in those with chemotherapy-induced neutropenia who showed a neutrophil response to treatment. In these patients, the lactoferrin:neutrophil ratio became elevated, suggesting increased synthesis/release of lactoferrin from neutrophils. However, patients with myelodysplasia continued to show depressed lactoferrin:neutrophil ratios, even when there had been an increase in granulocyte count, suggesting persistent abnormalities of neutrophil lactoferrin production/release. The implications of these findings for treatment of neutropenic patients with granulocyte-macrophage colony-stimulating factors are discussed.