Breastfeeding is important for mammals, providing immunological and microbiological advantages to neonates, together with the nutritional supply from the mother. However, the mechanisms of this functional diversity in the mammary gland remain poorly characterized. Here, we show that, similar to the gastrointestinal tract, the mammary gland develops immune and microbial environments consisting of immunoglobulin A (IgA) and the microflora, respectively, both of which are important for protecting neonates and the mother from infectious diseases. The IgA production and microflora development are coordinated in the gastrointestinal tract but seem to be independently regulated in the mammary gland. In particular, the chemokine (C-C motif) ligand 28 and poly-Ig receptor, crucial molecules for the IgA production in milk, were expressed normally in germ-free lactating mice but were almost undetectable in postweaning mothers, regardless of the microflora presence. Our findings offer insights into potentially improving the quality of breastfeeding, using both immunological and microbiological approaches.

中文翻译：

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免疫和微生物环境的发展在乳腺中是独立调节的。

母乳喂养对哺乳动物很重要，它为新生儿提供免疫学和微生物学优势，以及来自母亲的营养供应。然而，乳腺中这种功能多样性的机制仍未得到充分表征。在这里，我们表明，与胃肠道类似，乳腺会形成分别由免疫球蛋白 A (IgA) 和微生物群组成的免疫和微生物环境，这两者对于保护新生儿和母亲免受传染病的侵害都很重要。IgA 的产生和微生物区系的发育在胃肠道中协调，但在乳腺中似乎是独立调节的。特别是趋化因子（CC 基序）配体 28 和多聚 Ig 受体，它们是牛奶中 IgA 生产的关键分子，在无菌哺乳小鼠中正常表达，但在断奶后的母亲中几乎检测不到，无论是否存在微生物群落。我们的研究结果提供了关于使用免疫学和微生物学方法可能提高母乳喂养质量的见解。