In this issue of The Journal, Triplett et al1 discuss the relationship among an established laboratory test (lupus anticoagulant), an experimental laboratory test (anticardiolipin antibody), and a clinical phenomenon (thrombosis). To understand the conclusion of their work, a little background is needed. They observe that the target of the anticardiolipin assay may be an "epitope" of the lupus anticoagulant. An epitope (from the Greek word for "nearby place") is an antigenic determinant, a structure that can be identified by an antibody. However, the antigenic determinant may be unrelated except by proximity, not by cause, to some other structure of interest.
See also p 550.
Why the interest in epitopes? There is rapidly increasing interest in using specific antibodies for both therapy2,3 and diagnosis. With the development of monoclonal antibodies, much smaller targets can be used. An antibody to a given molecule may be directed only to part of
J. David Bessman. Epitopes in MedicineThe Example of the Lupus Anticoagulant. JAMA. 1988;259(4):573. doi:10.1001/jama.1988.03720040065031