1.乳汁中的分泌型IgA: 分泌型IgA是初乳中显著的蛋白质,其含量约为10g/L,在一周后降为1～2g/L,与此同时,乳汁的量却增加。在大多数授乳过程中,母乳喂养的婴儿,每24小时获得的分泌型IgA的总量为1g。人乳中,IgG及IgM的含量约为分泌型IgA的1％,而IgD和IgM仅微量存在。乳汁IgA抗体可针对许多种细菌、病毒、寄生虫和食物抗原,其中大部分均可侵犯肠粘膜,实验动物和人类的研究已揭示了有一个“肠一乳轴”(entero- 1. Secretory IgA in milk: Secretory IgA is a significant protein in colostrum, its content is about 10g / L, reduced to 1 ~ 2g / L after a week, while the amount of milk is increased. In most breastfeeding infants, the total amount of secreted IgA obtained every 24 hours is 1 g. Human milk, IgG and IgM content of about 1% of secreted IgA, while only a small amount of IgD and IgM exist. Milk IgA antibodies can target many types of bacteria, viruses, parasites and food antigens, most of which can invade the intestinal mucosa. Studies in laboratory animals and humans have revealed that there is an "entero-