Final answer:
Antigen-binding specificity of antibodies is determined by the variable domains, not the heavy chain constant regions, and is therefore independent of the antibody class.
Step-by-step explanation:
The property of antibodies that is independent of the structure of the heavy chain constant regions is antigen-binding specificity. This is because antigen-binding specificity is determined by the variable domains of the antibodies, which are found in the heavy and light chains and form the antigen-binding sites. The constant region of the heavy chain, however, dictates the class of the antibody (e.g., IgG, IgM, IgA, IgD, IgE) and influences functions like opsonization, complement activation, and class switching.
Different antibody classes, characterized by their constant domains, have distinct roles in the immune response. For example, IgM is a first responder during an immune reaction and is effective at activating the complement cascade, whereas IgG can be produced through class switching and continues to be involved in the immune response with the same antigen specificity.