Detection of distant antigenic relationships between insect and bird lysozymes by ELISA

We used an indirect enzyme-linked immunosorbent assay (ELISA) for measuring the immunological cross-reactivities between bird lysozymes and a lysozyme isolated from the blood of the insect Locusta migratoria. The degrees of cross-reactivity among five avian lysozymes measured by ELISA agreed approximately with those observed in earlier work using microcomplement fixation tests. This latter technique is not suitable for detecting immunological cross-reactivity between proteins that differ in sequence by more than 30%-40%. In contrast, ELISA is able to detect distant relationships between antigens such as lysozymes that differ in sequence by as much as 60%. It seems likely that the use of ELISA procedures will extend the range of homologous proteins that can be compared by immunochemical means.