Cummins A G, Thompson F M
Gastroenterology Unit, Queen Elizabeth Hospital, Australia.
Immunol Cell Biol. 1997 Oct;75(5):419-29. doi: 10.1038/icb.1997.67.
There are profound changes of immune activity during infancy from suppression during breast feeding, activation with weaning, and later intrinsic down-regulation after weaning. Breast feeding, as well as protecting against infections, seems to have a fundamental role in modifying the immune system against certain disease states. Transforming growth factor (TGF)beta in breast milk may mediate this immunosuppressive effect. Although the infant immune system is not in an adult state, the notion that the infant immune system is immature is difficult to reconcile with evidence that most infants respond appropriately to immunization and to infections. The systemic immune system of neonates may be subject to Th2 immune deviation, while the mucosal immune system, particularly of the gastrointestinal tract and probably the respiratory tract, is up-regulated with physiological inflammation during infancy. Weaning is associated with a peak of intestinal immune activation which includes mucosal mast cells and T cells. The physiological effects of this activation are promotion of epithelial growth of the small intestine and initial activation of mechanisms leading to subsequent down-regulation of the physiological heightened immune activity. This coincides with the development of mucosal (oral) tolerance to food and bacterial antigens.
婴儿期免疫活动会发生深刻变化，从母乳喂养期间的免疫抑制，到断奶时的免疫激活，以及断奶后内在的免疫下调。母乳喂养除了能预防感染外，似乎在调节免疫系统以抵御某些疾病状态方面具有重要作用。母乳中的转化生长因子（TGF）β可能介导这种免疫抑制作用。尽管婴儿免疫系统并非处于成人状态，但婴儿免疫系统不成熟这一观点很难与大多数婴儿对免疫接种和感染能做出适当反应的证据相协调。新生儿的全身免疫系统可能会出现Th2免疫偏移，而黏膜免疫系统，尤其是胃肠道以及可能还有呼吸道的黏膜免疫系统，在婴儿期会随着生理性炎症而上调。断奶与肠道免疫激活高峰相关，其中包括黏膜肥大细胞和T细胞。这种激活的生理效应是促进小肠上皮生长，并启动导致随后生理性增强的免疫活动下调的机制。这与对食物和细菌抗原的黏膜（口服）耐受性的发展相吻合。
