IDENTIFICATION OF A DOG IGD-LIKE MOLECULE BY A MONOCLONAL-ANTIBODY

IgD has not been identified in dogs. We produced a monoclonal antibody (mAb) designated 9B during the production of hybridomas to dog IgE. U sing Western blot analysis under non-reducing conditions, the mAb (9B) recognized a predominant protein band of 185 kDa which was also recog nized by anti-dog IgG F(ab')(2), suggesting that this 185 kDa protein is an immunoglobulin (Ig) containing light chains. Under reducing cond itions, the mAb (9B) recognized only one protein band of 55 kDa which presented a distinct molecular weight (MW) and immunoreactivity from t he dog tau, mu, alpha, and epsilon chains. The 55 kDa band did not rea ct with anti-dog IgE, IgM, IgA, and IgG, but did react with the mAb (9 B). The MW was 75 kDa for the epsilon chain, 77.5 kDa for the mu chain , 58 kDa for the alpha chain, and 52 kDa for the tau chain. Further, b y immunofluorescent staining, this Ig recognized by the mAb (9B) was f ound on the surface of dog lymphocytes. Studies of this dog Ig with th e mAb revealed that this Ig bound to protein A and protein G-Sepharose , and that its enzyme-linked immunosorbent assay (ELISA) activity as m easured by the mAb (9B) did not change after heating at 56 degrees C f or 2 h. Ragweed-specific IgG, IgE, and this newly defined Ig significa ntly increased when dogs were immunized with ragweed extract. These da ta suggest that this Ig is a previously unrecognized IgD-like molecule in dogs.