Studies have shown that immune components of human milk can be changed during an infection in the nursing infant. Macrophages are abundant in human milk and they are classified into inflammatory (CD16-) and noninflammatory (CD16+) subsets. This study investigated CD16+ and CD16- macrophage homing into breast milk in response to ongoing infections in nursing infants. Peripheral blood and mature milk were collected from 33 healthy mothers of nursing infants with respiratory infections (Group I) and from 26 healthy mothers of healthy nursing infants (Group H). Blood and milk total, CD16- and CD16+ monocyte (Mo)/macrophage (Mφ) subsets, respectively, and CCR2 and CX3CR1 expression and cytokine levels were analyzed by flow cytometry. CCL2 and CX3CL1 were quantified by ELISA and cytokines by flow cytometry in serum and milk. There was an increase of total and CD16+ Mφ, and, also a decrease of CD16- Mφ frequencies in maternal milk from Group I compared to Group H, but absolute numbers analyses showed higher numbers of all subpopulations of milk Mφ in Group I compared to Group H. Higher numbers of CX3CR1+CD16+ and double-staining of CCR2 and CX3CR1 in both CD16+ and CD16- cells were observed in milk during infant infection, which weren't observed in the blood. CCR2 expression was hardly found in milk CD16- Mφ in both groups. CCL2 and CX3CL1 were both higher in milk than in blood from both groups, but Group I showed higher levels of these chemokines in milk than Group H. Breast milk showed higher IL-6 and IL-8 concentrations than serum, and infant infection caused an increase in these cytokines only in milk. Our findings suggest that milk Mφ profiles are different from blood Mo, and the ongoing infection in the nursing infant could change milk Mφ to a more anti-inflammatory profile compared to that in the healthy group, possibly as an additional strategy of infant protection.

中文翻译：

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巨噬细胞谱和归巢到母乳中以应对哺乳婴儿的持续呼吸道感染

研究表明，母乳中的免疫成分在哺乳婴儿感染期间会发生变化。巨噬细胞在人乳中含量丰富，可分为炎性 (CD16-) 和非炎性 (CD16+) 亚群。本研究调查了 CD16+ 和 CD16- 巨噬细胞在哺乳婴儿持续感染时归巢到母乳中的情况。外周血和成熟乳来自 33 名患有呼吸道感染的哺乳婴儿的健康母亲（I 组）和 26 名健康哺乳婴儿的健康母亲（H 组）。通过流式细胞术分析血液和乳汁总量、CD16- 和 CD16+ 单核细胞 (Mo)/巨噬细胞 (Mφ) 子集，以及 CCR2 和 CX3CR1 表达和细胞因子水平。CCL2 和 CX3CL1 通过 ELISA 定量，细胞因子通过流式细胞术在血清和牛奶中定量。与 H 组相比，I 组母乳中的总和 CD16+ Mφ 增加，CD16-Mφ 频率也降低，但绝对数量分析显示，与组相比，I 组中所有乳 Mφ 亚群的数量更高H. 在婴儿感染期间，在牛奶中观察到更多 CX3CR1+CD16+ 和 CCR2 和 CX3CR1 双重染色，CD16+ 和 CD16- 细胞中的 CD16+ 和 CD16- 细胞中，这在血液中没有观察到。两组的乳CD16-Mφ中几乎没有发现CCR2表达。两组的牛奶中的 CCL2 和 CX3CL1 均高于血液，但 I 组的牛奶中这些趋化因子的水平高于 H 组。母乳中的 IL-6 和 IL-8 浓度高于血清，婴儿感染导致这些细胞因子仅在牛奶中增加。