Serum Myeloperoxidase and Lactoferrin in Neutropenia

Abstract

Radioimmunosorbent assays for determination of serum content of the neutrophil proteins myeloperoxidase and lactoferrin are described. Serial studies were performed in patients with neutropenia. In 2 cases of cyclic neutropenia, the myeloperoxidase level showed slight variations within the normal range during the cycle while lactoferrin displayed a clear correlation with neutrophil counts. In 1 case with persistent agranulocytosis, myeloperoxidase was normal but lactoferrin was extremely low. During the regeneration phase of drug-induced neutropenia, neutrophil counts and serum lactoferrin increased in a parallel fashion. Since serum myeloperoxidase was normal during profound neutropenia, it may be derived primarily from myeloperoxidase-rich granulopoietic precursor cells of the marrow. Serum lactoferrin seems to be derived from leakage of more mature granulopoietic cells of blood and marrow. Studies of neutrophil proteins of serum may aid in evaluation of neutropenic patients.