Characterization of an antiserum specific for the Fabalpha fragment. Its use for detection of alpha-heavy chain disease protein by immunoselection.

An antiserum to the Fabalpha fragment of human IgA was prepared by injecting K-and lambda-type IgA1 myeloma protein Fab fragments in complete Freund's adjuvant into a goat. After appropriate absorptions, the antiserum reacted specifically with Fabalpha fragments, normal IgA, and K- and lambda-type IgA1 and IgA2 myeloma proteins. This antiserum contained predominantly antibodies to determinants shared by different IgA myeloma proteins and expressed on isolated alpha chains. These determinants were presumably located on the first constant domain of the alpha chain (Fd fragment). When incorporated into agarose, the anti-Fabalpha antiserum is a potentially valuable reagent for screening human sera for alpha-heavy chain disease proteins by an immunoelectrophoretic method of immunoselection.