Serum levels of major basic protein in patients with or without eosinophilia: measurement by enzyme‐linked immunosorbent assay

A bone marrow proteoglycan (BMPG) has been purified which consists of the same amino acid sequence as that of pro-MBP, and produced two anti-BMPG mAbs. Serum levels of major basic protein (MBP), a cationic protein rich in the eosinophil granule, were measured in patients with eosinophilia or allergic diseases by an enzyme-linked immunosorbent assay (ELISA) using these mAbs. The serum levels of MBP in patients with eosinophilia (n = 64) and in those with allergic diseases without eosinophilia (n = 32) were elevated significantly (P < 0.001 and P = 0.038, respectively). There was a weak positive correlation between the serum levels of MBP and the eosinophil counts in the patients with eosinophilia (r = 0.38). Among these patients, extremely high serum levels of MBP were found in those with hypereosinophilic syndrome (HES) and Kimura's disease. Serum levels of MBP decreased more slowly than the eosinophil counts in patients with eosinophilia when treated by glucocorticoids. We conclude that measurement of serum levels of MBP is useful in evaluating the total-body proliferation and infiltration of eosinophils more accurately than following-up the eosinophil counts alone.