Abstract
The haemolysin of measles virus, either in the virion or in infected cells, is functionally and antigenically sensitive to acetone. Absorption of human sera with acetone-treated, measles virus-infected cells removes antibodies to all measles virus structural antigens except haemolysin. The antibody titres of absorbed sera give good correlation in HLI, neutralization and fluorescent antibody staining on unfixed infected cells.