Monoclonal antibodies against porcine immunoglobulin isotypes

Monoclonal antibodies (MCAs) against porcine immunoglobulin isotypes* G, G1, G2, M and A have been produced and characterized in detail. Epitope analysis using a competitive direct enzyme-linked immunosorbent assay (ELISA) indicated that the MCAs recognized 3 class-specific epitopes of IgG, 4 epitopes specific for IgG1, 3 epitopes specific for IgG2, 2 epitopes of IgM and 2 epitopes of IgA. Two MCAs against IgG2 were shown to react with an allotypic determinant (B2) and one MCA against IgM is probably allotype specific. The production of MCAs specific for IgG and for its subclasses G1 and G2 and, in addition, the one-step isolation of nearly pure IgG1 and IgG2 preparations by immunoaffinity chromatography using MCA 34.1.1a (anti-IgG2) confirmed the existence of at least two subclasses of IgG. Preliminary results further suggested the existence of a subpopulation of IgG1 which could be eluted selectively from Protein A-Sepharose columns at pH 5.0. MCA 34.17.2a appeared to react preferentially with this IgG1 subpopulation and could be used to isolate a similar IgG1 subpopulation by immuno-affinity chromatography. Several of the MCAs have been successfully applied for the detection of porcine immunoglobulin isotypes by a double antibody sandwich ELISA and for the (isotype-specific) detection of antibodies against various porcine viruses. The availability of a full set of MCAs against porcine immunoglobulin isotypes will stimulate and facilitate the further study of the porcine immune system.