Functional capacity of immunoglobulin G preparations and the F(ab')2 split product

Five immunoglobulin G preparations, including one 5S F(ab')2 split product, were compared for activity against common bacterial, viral, and protozoan pathogens. Standard assays were used to quantitate antibodies to tetanus, diphtheria, cytomegalovirus, herpes simplex virus types 1 and 2, rubella virus, and Toxoplasma gondii. Opsonization and killing of bacteria were examined by chemiluminescence methods using Streptococcus pneumoniae types 5, 12F, and 14 and Staphylococcus aureus. Antibodies to the viral pathogens and T. gondii were not detectable for the 5S immunoglobulin even at high concentrations (50 mg/ml) but were present in all 7S preparations at immunoglobulin concentrations of 10 mg/ml. Relatively lower activities for tetanus and diphtheria antibody were also seen with the F(ab')2 product. Opsonizing capacity against all pneumococcal serotypes and Staphylococcus aureus was lowest for the 5S product and highest for the commercially available intravenous immunoglobulin product that is purified by using a pH 4.25 formulation. These data do not support potential clinical usefulness of immunoglobulin G split products and suggest wide variations of specific antibody among commercial intravenous immunoglobulin preparations.