The source of serum ferritin during infection. Studies with concanavalin A--Sepharose absorption

1. Serum samples were collected from ten patients hospitalized for acute infections and from a control group of seven normal subjects. Tissue ferritin was obtained by purification of ferritin from normal human liver and from the ferritin standard of a commercially available assay kit. 2. The serum and tissue samples were incubated with concanavalin A--Sepharose, which has the ability to bind normal serum ferritin. 3. Concanavalin A, a plant lectin which binds to glucose, can be coupled to Sepharose particles and by incubation and centrifugation ferritin in normal serum can be absorbed to about 70%. The serum and tissue samples were incubated with concanavalin A--Sepharose and the ferritin content was measured before and after. 4. It was found that ferritin in the serum of patients with acute infections was absorbed to the same extent as in normal serum (about 80%), irrespective of the initial value. Only about 20% of the tissue ferritin was absorbed. 5. It is concluded that the ferritin in serum during infection is of the same glucosylated type as the ferritin normally present in serum, whereas intracellular ferritin is not glycosylated. This indicates that the elevation of serum ferritin during infection is caused by a release along the normal pathways, i.e. an augmented synthesis, not by leakage from damaged cells.