ABSTRACT
Autoantibodies are immunoglobulins that bind via their combining sites to antigens originating in the same individual or species (autoantigen). The specificity of the antibody is conveyed by the variable regions of the heavy and light chains, whereas the biological properties are dictated by the constant region of the heavy chains. Any antibody binding to a self antigen becomes by definition an autoantibody, the binding may or may not be relevant to autoimmune diseases. Natural antibodies are immunoglobulins that occur in normal individuals of several species and bind to a variety of self proteins. It may be these autoantibodies that serve a beneficial role in helping to clear self molecules from the circulation. The significance of an autoantibody should, therefore, be evaluated by considering the antibody, the antigen and the assay used for detection. Important features of the antibody are its class, valence, titer, clonality, and affinity.
