Antibodies to type III group B streptococcal polysaccharide in breast milk.

We compared concentrations of type III group B streptococcal capsular polysaccharide (CPS)-specific IgG and IgA in archived 2-month-postpartum breast milk from 9 women with > or =1 microg/ml and 9 with < 1 microg/ml type III CPS-specific IgG in serum. Type III CPS-specific antibodies were not detectable consistently but were measurable in breast milk from some women in both groups, indicating their potential for a role in prevention or amelioration of late onset group B streptococcal disease.