A novel cell surface antigen, 4C8, is expressed on human eosinophils

BACKGROUND: A novel monoclonal antibody, anti-4C8, reacted with human peripheral lymphocytes and monocytes but not with neutrophils. In this study, we investigated whether the 4C8 antigen is expressed on human peripheral eosinophils. METHODS: Expression of the 4C8 antigen on eosinophils was analyzed by flow cytometry and molecular analysis of the antigen was performed with eosinophils by Western blotting. RESULTS: Among human peripheral granulocytes, the 4C8 antigen was expressed on CD16-negative cells but not on CD16-positive cells. The 4C8 antigen also appeared to be expressed on eosinophils. To confirm the latter finding, eosinophils were purified from peripheral blood. On flow cytometric analysis, anti-4C8 antibody reacted with purified eosinophils. On Western blotting analysis, anti-4C8 reacted with a single band of 80 kDa in lysates from purified eosinophils. The correlation between the percentage of eosinophils determined by May-Giemsa staining and the percentage of 4C8-positive/CD16-negative cells among granulocytes was good (r = 0.91, P < 0.0001). CONCLUSIONS: Only a few cell surface antigens are available to distinguish human peripheral eosinophils from neutrophils. The novel cell surface antigen, 4C8, is a useful new marker of human eosinophils.