Abstract
Extract: Immunoglobulin (Ig) A antibodies to Bacteroides fragilis and Escherichia coli in breast fluids and serum of lactating women, and IgG antibodies to E. coli in cord and maternal sera of mother-infant pairs were measured by a radioimmunoassay. Antibody concentrations were expressed as micrograms of antibody per milliliter or per milligram of IgA or IgG. For concentrations (mean ± SD) of IgA antibodies, see Table 1.
Concentrations of secretory IgA in breast fluids were 36.7 ± 25.3 mg/ml on day 1, 1.66 ± mg/ml on day 4, and 0.71 ± 0.31 mg/ml 6 weeks after delivery. Both the amount of IgA antibodies (μg/ml) and total IgA in colostrum fell abruptly and reached serum levels by the 4th postpartum day. The 23–30-fold greater quantity of IgA antibodies per milliliter for day 1 colostrum than IgA antibodies per milliliter of serum at delivery corresponded to a 21-fold higher total concentration of IgA in colostrum than in serum at these times. Concentrations of antibodies to B. fragilis and E. coli were not significantly different.
Concentrations of IgG antibodies to E. coli in 10 maternal sera at delivery (2.1 ± 1.6 μg/ml; 0.33 ± 0.29 μg/mg IgG) were slightly but not significantly lower than those in corresponding cord sera (2.5 ± 2.0 μg/ml; 0.29 ± 0.22 μg/mg IgG). Concentrations of serum IgA anti-E. coli antibodies were similar in nursing and non-nursing mothers both at delivery and 6 weeks later, and these concentrations were similar to those in nonpregnant women.
Findings of the study indicate that (1) the large quantities of IgA antibodies to E. coli and B. fragilis in colostrum result from the presence of large quantities of IgA rather than from IgA that is richer than serum IgA in specific antibodies; (2) concentrations of IgA antibodies to E. coli and B. fragilis in maternal serum and colostrum are similar, even though Bacteroides greatly outnumber coliforms in gut contents of adults; (J?) concentrations of IgG antibodies to E. coli are similar in maternal and fetal circulation; (4) nursing and pregnancy do not influence concentrations of serum IgG antibodies to the bacteria studies.
Speculation: During lactation, the breast synthesizes IgA with constant levels of specific antibodies to commensal intestinal bacteria. Ingested breast fluid antibodies to B. fragilis could suppress growth of Bacteroides in the gut and account for the relatively low numbers of these anaerobes in intestinal content of breast-fed infants.
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Ste-Marie, M., Lee, E. & Brown, W. Radioimmunologic Measurements of Naturally Occurring Antibodies. III. Antibodies Reactive with Escherichia coli or Bacteroides fragilis in Breast Fluids and Sera of Mothers and Newborn Infants. Pediatr Res 8, 815–819 (1974). https://doi.org/10.1203/00006450-197409000-00008
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DOI: https://doi.org/10.1203/00006450-197409000-00008