SummaryThe protective value of pooled human gamma globulin (GG) and a group B streptococcal immune globulin (GBSIG) was studied in a chick embryo and a murine model of group B streptococcal (GBS) infection. Chick embryos were protected by the IV administration of 0.4 to 0.8 mg of GG from three manufacturers against IV challenge with type Ia GBS. Two of three GG preparations at doses of 0.4 to 1.65 mg protected chick embryos against type III, but 1.65 mg of all three preparations failed to protect against GBS types Ib and II. Mice were protected from lethal IP challenges with types Ia and Ib by the prior IM inoculation of three and two of the three GG preparations at doses of 0.5 to 1.0 mg, respectively. Administration IM of 1 mg of GG failed to protect mice against types II and III.The IV administration of 0.2 mg of GBSIG protected chick embryos against IV inoculation with GBS types Ia, Ib, II, and III. Administration IM of 0.5 mg of GBSIG protected mice against IP challenges with types Ia, Ib, and II, but not with type III. The IP administration of 0.25 mg of GBSIG simultaneously with type III GBS protected mice, whereas GG was not protective. GBSIG should undergo clinical trials for the prevention of GBS infections and their recurrences and as a possible adjunct to antibiotic and supportive therapy of severe GBS infections.SpeculationSome human sera contain antibody which protects animals against infection with group B streptococcus. If passive immunization with human gamma globulin or group B streptococcal immune globulin is effective in animal models, it may be potentially useful in preventing neonatal group B streptococcal infections, and clinical trials would be indicated.