IgG4 antibodies will dominate the IgG response in schistosomiasis, lymphatic filariasis, and in patients after allergen immunotherapy. Unlike the other IgG subclasses, IgG4 does not activate complement. A combined IgA-IgG4 deficiency has been associated with recurrent pyogenic infections. Prepared from myeloma plasma shown to be non reactive for HbsAG, anti-HCV, anti-HBc, and negative for anti-HIV 1 & 2 by FDA approved tests. >95percent pure by SDS-PAGE.