Baby and breast: a dynamic interaction

In a comparison of before and after white blood cell, cytokine, immunoglobulin A (IgA), and lactoferrin responses in milk of mothers of babies with putative infectious illness vs. controls, Riskin et al. (1) have found that during active infection in the nursing infant, the total number of white blood cells—specifically, the number of macrophages—and levels of tumor necrosis factor-α increase. This study supports a very dynamic interaction between an infant' s health status and the mother's response that likely enhances the immunologic defenses of the mother's milk.

This interplay between the infant's health status and the response in the mother's milk is highly reminiscent of the concept that Kleinman and Walker (2) introduced more than 30 years ago, termed the “enteromammary system.” In their conceptual framework, antigen presented from the infant to the maternal gut via contact between the mother and the baby is brought into proximity to the mother's lymphoid follicles, which in turn commit lymphoblasts to specific IgA production, which then migrate to the breast and secrete sIgA, which is ingested by the infant. Furthermore, in this concept, T cells, B cells, and macrophages are also thought to extrude into the breast milk and are immunologically active. However, at the time the “enteromammary system” was conceptualized, the basis was primarily studies done in animals. The present study supports this concept nicely by showing responses in human infant mothers' milk (consisting of increased white blood cells, primarily macrophages, tumor necrosis factor-α to infectious illness thought to originate from the infant.