Dissection of antibody-antigen interactions requires a knowledge of an
tibody structure, the ability to model accurately the conformation of
antibody-combining sites, and an understanding of the energetic factor
s governing the interactions. When this understanding has reached the
point where the molecular shape and chemical character of a combining
site necessary to define a particular specificity and binding requirem
ent can be designed, the antibody repertoire will have been extended '
beyond the natural limits'.