Comparative opsonic activity of intravenous gamma globulin preparations for common bacterial pathogens

Immune globulin intravenous is a reduced and alkylated preparation of gamma globulin that is stabilized in 10 percent maltose and 0.1 M glycine at pH 6.8. Recently, a modified immune globulin intravenous preparation was developed that is identical to the standard preparation except that it does not contain glycine and the pH has been lowered to 5.25. The effect of these modifications has resulted in a higher IgG monomer content in the preparation. In the present studies the opsonic activity against several common bacterial pathogens was assessed in the standard (pH 6.8) versus the more acidic immune globulin intravenous (pH 5.25). Opsonic activity was detected in each preparation for Staphylococcus aureus, group B streptococci, Pseudomonas aeruginosa, Escherichia coli, and Serratia marcescens. With all of the organisms except S. marcescens, an intact complement system was required for optimal uptake and killing with each preparation. In general, the opsonic activity of the pH 5.25 immune globulin intravenous was equivalent to the standard pH 6.8 preparation. With several organisms, however, the more acidic preparation had greater activity than the standard one. An immune globulin intravenous preparation with increased antibody titers to P. aeruginosa was also prepared from selected donors and tested for opsonic activity against six of the seven Pseudomonas immunotypes. This preparation was found to have strikingly increased opsonic titers for most of the Pseudomonas immunotypes when compared with the standard immune globulin intravenous. These studies indicate that changes in donor selection or minor modifications in production techniques may markedly affect the biologic activity of intravenous gamma globulin.