Treatment of pregnant mice with antibiotics modulates the humoral response of the offspring: role of prenatal and postnatal factors.

This study was designed to determine the role of prenatal and postnatal factors underlying altered humoral response of the offspring of mice treated with antibiotics during pregnancy. Pregnant random-bred NMRI mice were administered i.p. from the 11th to 15th day of pregnancy with a mixture of ampicillin and cloxacillin (2:1) in a daily dose of 21 mg/kg body weight. The litters of experimental and control mothers were cross-fostered at birth and the offspring were immunized on the 23rd or 24th postnatal day with SRBC. The primary humoral response was assayed using spectrophotometric determination of SRBC lysis mediated by anti-SRBC IgM antibodies produced by spleen cells. The offspring born of saline-treated mothers and transferred to mothers treated with antibiotics, as well as the offspring born to mothers treated with antibiotics and transferred to mothers treated with saline, produced significantly higher amounts of spleen anti-SRBC IgM than the control offspring. The results suggest that the immune response of the offspring was modulated by both the prenatally and postnatally acting factors, the latter being mediated by effects of antibiotics on the maternal organism.