Transfer of food allergen to breast milk and its physiological significance

为了阐明母乳致敏的机制，对母乳中的食物过敏原进行了分析。在凝胶过滤实验的人母乳中，主要的食物过敏原，卵类粘蛋白（28 kDa）的鸡蛋，洗脱在一个分子量约为450 kDa的馏分，这对应于卵类粘蛋白和sIgA的免疫复合物。类似的结果显示，食物过敏原作为免疫复合物与母乳中的特异性sIgA一起出现，也在其他食物如牛奶、小麦、荞麦和花生中观察到。这种现象本身并不是婴儿过敏的直接原因，因为母乳中免疫复合物的种类和水平与婴儿喝了母乳后过敏之间没有合理的关系，但在极少数情况下，在母乳中发现了游离的食物蛋白质，这可能是过敏原。用过量的β-乳球蛋白孵育母乳，导致其与sIgA的免疫复合物增加，其游离sIgA减少，而不影响sIgA对卵类粘蛋白的模式。母亲喂养荞麦诱导的sIgA特定的荞麦蛋白在母乳中的水平。可能的生理重要性，这些研究结果进行了讨论，与婴儿肠道免疫的发展。

To clarify the mechanism of allergy sensitization via breast milk, food allergens in human breast milk were analyzed. On gel-filtration experiments of human breast milk, the major food allergen, ovomucoid (28 kDa) of hen's egg, was eluted at the fractions with a molecular weight of about 450 kDa, which corresponded to that for the immune complex of ovomucoid and sIgA. Similar results, showing the occurrence of a food allergen as an immune complex with its specific sIgA in breast milk, have also been observed for other foods such as cow's milk, wheat, buckwheat, and peanut. This phenomenon itself would not be a direct cause of baby's allergy because there was no reasonable relationship between the kind and level of the immune complex in mother's milk and the allergy of the baby who drank it. In the very rare case, however, free food proteins were found in breast milk, which might act as allergens. Incubation of breast milk with excess amount of β-lactoglobulin resulted in the increase of its immune complex with sIgA and decrease of its free sIgA without affecting the pattern of the sIgA against ovomucoid. Maternal feeding of buckwheat induced the level of the sIgA specific to buckwheat proteins in breast milk. Possible physiological importance of these findings is discussed in connection with development of intestinal immunity of infants.