Successive extraction of specific protective immunoglobulins from pooled human sera.

By use of pooled human sera, specific protective immunoglobulins against the Smith-diffuse strain of Staphylococcus aureus, strains SS-620 and SS-619 of types III and II group B streptococci, and strain K-9 of Klebsiella pneumoniae were successively extracted from their whole cell and antibody complexes by elution with propionic acid containing 5% sucrose. Injection of 0.14, 0.05, 0.09, and 0.15 mg of these eluates in mice gave protection against lethal infection only with homologous strains. However, no protective effect was observed against these infections, even with considerably higher amounts of a conventional immunoglobulin preparation. The major components of the eluates were the three major immunoglobulins, immunoglobulin G (IgG), IgA, and IgM, although nonspecific proteins were also included. Protective activities of these eluates were absorbed out by their protection-inducing antigens, indicating that they contained specific protective immunoglobulins.