Maternal blood B-cell (CD19+) percentages and serum immunoglobulin concentrations correlate with breast-feeding behavior and serum prolactin concentration

PROBLEM: Lactating women recover from pregnancy-induced immunosuppression while actively secreting immunologically active agents into milk. Few clinical studies have examined changes in postpartum maternal immune status or explored mechanisms. METHOD OF STUDY: We measured blood B-cell (CD19+) percentages and serum concentrations of immunoglobulin (Ig) G, IgM, and IgA at I to 2 weeks, I month, and 2 months postpartum in a longitudinal study of seven healthy, lactating women. RESULTS: More frequent or extended breast-feeding sessions were correlated with lower CD19+ percentages, reduced serum IgG, and higher serum IgA and IgM concentrations. CD19+ percentages were correlated negatively with serum prolactin concentrations. Blood samples drawn before and 30 min after breast-feeding did not differ in CD19+ percentages or serum Ig concentrations. CONCLUSIONS: These findings confirm our previous cross-sectional study showing a negative correlation between CD19+ percentages and serum prolactin. Because lactation practices are modifiable, these findings suggest that women can influence the course of lactation-associated immunologic changes.