Evidence for Fc receptors on rabbit yolk sac endoderm
Evidence for Fc receptors on rabbit yolk sac endoderm
复制标题
兔卵黄囊内胚层 Fc 受体的证据
作者：
A. Wild;Pat Dawson
红细胞抗体玫瑰花结技术（EA玫瑰花结）在小鼠卵黄囊膜细胞培养中的应用提供了该物种卵黄囊内胚层上存在Fc受体的证据1。免疫球蛋白 (Ig) 与 Fc 受体的结合构成了 Brambell2 提出的假设的一个组成部分，该假设解释了抗体的选择性母婴传递。在这个假设中，当运输内吞小泡（根据物种不同，在合体滋养层、卵黄囊内胚层或肠道肠细胞中）与溶酶体融合后接触蛋白水解酶时，受体会保护附着的 Ig。关于抗体穿过小鼠卵黄囊内胚层的选择性转运知之甚少，也不清楚这些结果在多大程度上显示出 Ig 穿过内胚层细胞转运的特异性结合，或者仅仅反映了内吞此类特定蛋白质的某些特殊机制。对兔卵黄囊内胚层的研究尚未表明 Ig 是否发生特异性结合；因此，牛 IgG 虽然很容易被内吞 5，但在兔卵黄囊内胚层 3,4 上的运输较差，但与从细胞中分离的膜成分的结合程度与兔 IgG 相同6。另一方面，与兔 IgG 相比，当这些蛋白与福尔马林固定的兔卵黄囊体外孵育时，发现牛 IgG 的特异性结合相对较少。我们现在将 EA 玫瑰花结技术应用于兔卵黄囊内胚层，并发现 Fc 受体既能结合兔和人 IgG，但不能结合牛 IgG，这表明它们与选择性 Ig 转运有关。
APPLICATION of the erythrocyte-antibody rosette technique (EA rosette) to cell cultures of mouse yolk sac membranes has provided evidence of Fc receptors on yolk sac endoderm of this species1. Binding of immunogloibulin (Ig) to Fc receptors forms an integral part of a hypothesis proposed by Brambell2 to account for selective materno–foetal transmission of antibodies. In this hypothesis the receptor protects attached Ig when a transporting endocytotic vesicle (be it in syncytiotrophoblast, yolk sac endoderm, or gut enterocytes, according to the species) contacts proteolytic enzymes after fusion with lysosomes. Little is known about selective transport of antibodies across mouse yolk sac endoderm and it is not clear1 to what extent these results show binding specific for transport of Ig across the endodermal cells, or merely reflect some special mechanism for endocytosing this particular class of proteins. Studies of rabbit yolk sac endoderm have not shown whether specific binding of Ig takes place; thus bovine IgG, which is poorly transported across rabbit yolk sac endoderm3,4, although readily endocytosed5, binds to the same extent as rabbit IgG to membrane components isolated from the cells6. On the other hand, compared with rabbit IgG, relatively little specific binding of bovine IgG was found when these proteins were incubated in vitro with formalin-fixed rabbit yolk sac7. We have now applied the EA rosette technique to rabbit yolk sac endoderm and find Fc receptors which bind both rabbit and human IgG, but not bovine IgG, pointing to their association with selective Ig transport.