Tsay D D, Schlamowitz M
J Immunol. 1978 Aug;121(2):520-5.
Quantitative measurements of the in vitro binding of 125I-labeled rabbit IgG (IgGR), and its Fab-1, Fab-2, and Fc fragments to receptors on the fetal rabbit yolk sac membrane (YSM) were carried out by incubating equimolar solutions (1 X 10(-5) M) of IgGR and of each of its fragments with formalin-fixed discs (3.5 cm2) of the YSM. It was found that 97, 4, 2, and 96 pmoles of IgGR, Fab-1, Fab-2, and Fc, respectively, were bound per YSM disc. Since the binding characteristics of intact IgGR were fully conserved in the Fc piece, the results establish that the YSM receptor for IgG is an Fc receptor. It was also shown that whereas IgGR retained its binding ability after exposure to stress (55 degrees C, 10 min), free Fc did not. These findings, together with knowledge of the IgG structure, imply that the YSM receptor recognition unit of IgGR resides in the CH2 domain of its Fc piece.
通过将等摩尔溶液（1×10⁻⁵M）的¹²⁵I标记兔IgG（IgGR）及其Fab-1、Fab-2和Fc片段与经福尔马林固定的兔胎儿卵黄囊膜（YSM）圆盘（3.5 cm²）孵育，对它们在体外与YSM上受体的结合进行了定量测量。结果发现，每个YSM圆盘分别结合了97、4、2和96皮摩尔的IgGR、Fab-1、Fab-2和Fc。由于完整IgGR的结合特性在Fc片段中完全保留，这些结果证实YSM上的IgG受体是Fc受体。还表明，虽然IgGR在暴露于应激（55℃，10分钟）后仍保留其结合能力，但游离Fc则不然。这些发现，连同对IgG结构的了解，意味着IgGR的YSM受体识别单元位于其Fc片段的CH2结构域中。
