PROBLEM: Recently, we reported increases in the production of interferon-γ (IFN-γ), interleukin-2 (IL-2), and IL-4 during the postpartum period. The present study was undertaken to investigate whether these increases might be explained by increased prolactin while breast-feeding.
METHOD: Whole blood from 41 women who were breast-feeding, 13 women not breast-feeding, and 31 healthy non-pregnant women was stimulated with phorbol 12-myristate 13-acetate and ionomycin, and the levels of cytokines in the supernatant were measured by enzyme-linked immunosorbent assay. Their serum levels of prolactin were measured by enzyme immunoassay.
RESULTS: Increases in IFN-γ, IL-2, IL-4, and IL-10 production were observed in women who were breast-feeding but not in women who were not breast-feeding. Serum levels of prolactin correlated with the levels of IFN-γ in culture supernatant.
CONCLUSIONS: These results suggest that breast-feeding induces production of cytokines and that IFN-γ production is enhanced by physiological concentrations of prolactin.