Immunoglobulin flexibility in complement activation

Next to antigen-binding, the interaction between antibody and complement is among the most familiar and well-studied of all immunological events. Now that many of the molecular details are known, antibody-mediated complement activation provides a fascinating example of the subtle relationship between protein structure and function. In this discussion, Arnold Feinstein and his colleagues are concerned with the initial step in the classical pathway of complement activation, namely the activation of the first complement component (C1) after it has bound to a site on the Fc portion of an antibody molecule, and in particular with the problem of how the site is made available in different antibody classes.