Low levels of eosinophil cationic proteins in patients with asthma.

Arginine-rich cationic proteins are a major constituent of the granules of eosinophil leucocytes. In healthy individuals, serum levels of cationic proteins were correlated with blood eosinophil-counts. In asthma patients blood eosinophil-counts were raised but serum cationic-protein levels were lower than expected. Some patients with intrinsic asthma had very low cationic-protein levels despite high eosinophilia. A challenge test in one patient caused a striking decrease in serum cationic proteins but no change in eosinophil-count. Assays of serum "eosinophil" cationic proteins may be useful in the differentiation of atopic and intrinsic asthma and may throw light on pathogenesis.