Total amount of ECP per eosinophil as indicator for the activity state of eosinophils

Eosinophil cationic protein (ECP) serum concentrations yield additional information regarding the activity of allergic diseases because ECP serum concentrations correlate very well with blood eosinophil counts. We established spontaneous serum ECP release per eosinophil during in vitro coagulation amounting to 0.03-0.5 pg per eosinophil. When comparing the ECP per eosinophil ratio with the eosinophil concentration, a decreasing trend of released ECP in serum was observed towards higher eosinophil counts. The total amount of extractable ECP in eosinophilic granulocytes is determined by means of extraction with application of a 0.5% Cetyl-trimethyl-ammonium-bromide solution. The total amount of extractable ECP in eosinophils amounts to 0.4-17 pg/eosinophil. Results showed a slight tendency to decrease with higher eosinophil counts. Irrespective of their concentration in blood, eosinophils were demonstrated to release 2-4% of their total ECP amount. It is concluded from experiments in this study that release during in vitro clotting or measuring the total amount of extractable ECP does not yield any additional diagnostic value in detecting the degree of activation in eosinophils.