Monoclonal antibody PHE425 is a particularly useful marker of swine immunoglobulin light chains. Based on Western blots, the antibody reacts exclusively with free light chains after chemical reduction, and with light chains on intact immunoglobulins. It has been validated for use in immunological techniques such as ELISA, Western blot or immunohistochemistry on formalin-fixed tissue sections, and can be used as primary or secondary reagent. Swine antibodies are organized and synthesized as in other mammals, with two kinds of light chains, kappa and lambda. The antibody has shown minimal cross-reaction with human and rabbit immunoglobulins, but it may cross-react with immunoglobulins from other species.