Naturally occurring autoantibodies to skeletal proteins from human red blood cells.

The IgG fraction of sera of healthy human subjects contains natural antibodies to cytoskeletal elements of the donors own red blood cell membranes. Autoantibodies to spectrin are characterized in more detail: their Fab portion binds to the antigen. Autoantibodies, affinity-purified on immobilized spectrin band 1, precipitate 0.4 microgram of spectrin dimer per 1 microgram of autoantibody. They bind to band 1 and cross-react with band 2 of spectrin as well as with breakdown products of spectrin on blots from separated membrane polypeptides. Autoantibodies purified on spectrin band 2 after absorption on band 1 do not cross-react with band 1. The evidence strongly suggests the existence of such autoantibodies in healthy human subjects. This finding indicates that autoantibody production to normally unexposed antigens is not suppressed in ontogeny. These anti-cytoskeleton autoantibodies may have a physiologic role in clearance of debris from lysed cells. Their existence may open a new understanding of elevated anti-spectrin autoantibody concentrations in diseases with different etiologies.