Objective: To evaluate the functional capacity of granulocytes and monocytes from pregnant and nonpregnant
women in relation to group B streptococcus (GBS) colonization status.
Methods: Engulfment of fluorescent GBS by peripheral blood phagocytes from GBS-colonized and noncolonized
women was measured by flow cytometry. Intracellular superoxiode generated in response to GBS challenge to
monocytes and granulocytes enriched from peripheral blood of these women was also measured by flow
cytometry, and extracellular superoxide was determined by colorimetric assay.
Results: Monocytes and granulocytes from pregnant, GBS-colonized women engulfed significantly greater
numbers of GBS than phagocytes from pregnant, noncolonized women. No difference in intracellular superoxide
production was detected between any of the groups of women; however, monocytes from pregnant, colonized
women released significantly more superoxide into the extracellular milieu than did granulocytes from the same
women. No differences in extracellular release of superoxide were observed among noncolonized women
whether they were pregnant or not.
Conclusions: Monocytes from pregnant, colonized women engulf more GBS and release more of the superoxide
into the extracellular environment, where it is unlikely to be an effective defense mechanism against intracellular
bacteria. This suggests that components of the innate immune system that should serve in a protective role may
function suboptimally, thereby contributing to the colonization process by GBS.