Intravenous immunoglobulin preparations: a comparative in vitro study of fc mediated functions

An ideal immunoglobulin (Ig) preparation intended for clinical use should be safe and efficacious. Efficacy depends on suitable levels of protective antibodies against pathogens and the functional integrity of the Ig molecule. In the present paper, the functional integrity of the Ig molecule was investigated in eight intravenous Ig preparations commercially available in our country and compared to an intramuscular preparation. The experimental approach included protein A and rheumatoid factor binding, complement activation and opsonic activity. Ultracentrifugation profiles were obtained for all Ig preparations in order to ascertain the presence of components other than the expected 7S monomeric IgG. Immune complexes were investigated with C1q solid phase and conglutinin assays. Results show that chemical treatments such as sulfonation or reduction-alkylation, and enzymatic treatment such as plasmin digestion, variably but consistently impair Fc-mediated functions. The present data emphasize the use of in vitro tests for assessing the suitability of Ig preparations for intravenous administration.