Enzyme Immunoassays and Related Techniques: Development and Limitations

Abstract

Enzyme immunoassay procedures, first reported in 1971, were initially used to quantitate antigen and subsequently antibody (Avrameas and Gilbert 1971a, b; Engvall and Perlmann 1971, 1972; Van Weemen and Schuurs 1971). The principles on which they were based were similar or even identical to those of radioimmunoassays. They therefore necessitated the use of a solid phase to separate the free antigen or antibody from the specific antigen-antibody complexes and were consequently termed heterogeneous enzyme immunoassays. In 1972, Rubinstein and collaborators (Rubinstein et al. 1972) reported an enzyme immunoassay which did not necessitate the use of a solid phase, since it was based on antibody-mediated changes in enzyme activity. This procedure was defined as a homogeneous enzyme immunoassay. As the present stage of development of these techniques only permits their application to small haptens, we shall confine the present review to heterogeneous enzyme immunoassays. However, since in the past few years several reviews and books have described these assays in detail (Avrameas 1976; Engvall and Pesce 1978; Feldmann et al. 1976; O’Beirne and Cooper 1979; Oellerich 1980; Maggio 1980), we shall only indicate their essential points very briefly here, concentrating mainly on their present development, potentialities, and limits.