Purification of human autoantibodies from cross-linked antigen immunosorbents.

A method is described whereby autoantibodies to the Sjögren's syndrome antigen La (SS-B) can be purified from re-usable immunosorbent columns constructed from covalently linked human autoantibodies to which the antigen is cross-linked. Previous attempts to link the antigen directly to CNBr-Sepharose beads resulted in loss of biological activity and thus each purification of antibody required fresh batches of antigen. The present technique is a significant improvement since the cross-linked immunosorbents prepared from a single batch of antigen can be re-used several times over a 6 month period. Furthermore F(ab')2 fragments of anti-La antibodies can be purified from pepsin-digested serum samples. These antibodies react in ELISA, Western blot and immunofluorescence in an identical way to serum and murine monoclonal anti-La antibodies and show no reaction with the Ro antigen. However, being of human origin the affinity-purified anti-La antibodies have the advantages of bearing the same idiotypes and reacting with the same antigenic epitopes as naturally occurring serum autoantibodies.