The serum levels of eosinophil cationic protein (ECP) are related to the infiltration of eosinophils in the tumours of patients with Hodgkin's disease.

We have previously described a relation between abundance of eosinophilic granulocytes in Hodgkin's disease (HD) tumours and poor prognosis. In order to further explore the importance of the eosinophilic infiltration, we immunohistochemically examined the presence of eosinophils, using the monoclonal antibodies EG 1 and EG 2, in the tumours of 54 newly diagnosed patients with HD and related the degree of infiltration to clinical characteristics and the serum levels of eosinophil cationic protein (S-ECP). S-ECP levels (upper normal value 16 micrograms/l) varied between 2.2 and 71.7 micrograms/l, mean 25.4 micrograms/l. There was an association (p = 0.01) between the number of eosinophils in the tumour tissue and S-ECP. S-ECP levels were also associated to high erythrocyte sedimentation rate (ESR, p < 0.01) and nodular sclerosis (NS) histology (p < 0.05), and there was a tendency of a correlation to bulky disease (p = 0.06). The number of eosinophils stained with EG 2 correlated to high ESR (p < 0.05), and to high leukocyte count (p = 0.02). A follow-up value of S-ECP after treatment was, in most of the cases measured, lower than the initial value. The high values of S-ECP in several patients with HD probably originates from eosinophils infiltrating the tumours. The same patients had a higher ESR and tended to have a more advanced stage and bulky disease. There are no significant correlations with disease-free and overall survival, as the follow-up time is short, and prognosis favourable.