Protection of mice against group Bstreptococcus type Ia by IgG components of a rabbit antiserum

IgG fractions were separated by ion exchange chromatography on DEAE-cellulose from hyperimmune rabbit sera prepared against a group Bstreptococcus type Ia mouse-virulent strain. 50g IgG in conjunction with ampicillin (200 mg/kg) protected mice more effectively against a lethal challenge than ampicillin (400 mg/kg) alone or ampicillin (200 mg/kg) combined with gentamicin (10 mg/kg), when administered up to 12 h after infection.