Denham S, Barfoot R, Jackson E
Section of Medicine, Institute of Cancer Research, Belmont, Sutton, Surrey.
Immunology. 1987 Sep;62(1):69-74.
The binding to rat splenic and peritoneal macrophages of affinity-purified monoclonal rat IgGs, representing all IgG subclasses, was measured by the direct binding of 125I-labelled proteins using an assay that did not require the removal of unbound Ig by washing. Only rat monomeric IgGs of the subclass IgG2b bound specifically and in large amounts to rat macrophages. The binding was temperature dependent and more IgG2b bound to the cells at 4 degrees than at 37 degrees. Spleen macrophages bound approximately 10 times more IgG2b than the same number of peritoneal macrophages, although the association constants (Kas) for the binding were similar for both types of macrophage. The calculated values for the Kas, which varied slightly with each experiment and increased with decrease in temperature, fell within the range 1.3-5.3 X 10(8) M-1; the number of binding sites was estimated as about 10(5)/splenic macrophage and 10(4)/peritoneal macrophage. The binding of 125I-IgG2b to splenic macrophages was inhibited only by unlabelled proteins of the IgG2b isotype and not by IgG1, IgG2a and IgG2c proteins. Soluble IgG2b-antigen complexes also bound to the FcR for monomer but a soluble IgG2a-antigen complex did not inhibit the binding of monomeric IgG2b.
采用一种无需通过洗涤去除未结合Ig的检测方法，通过125I标记蛋白的直接结合，测定了代表所有IgG亚类的亲和纯化单克隆大鼠IgG与大鼠脾脏和腹腔巨噬细胞的结合情况。只有IgG2b亚类的大鼠单体IgG能特异性且大量地与大鼠巨噬细胞结合。这种结合具有温度依赖性，在4℃时比在37℃时更多的IgG2b与细胞结合。脾脏巨噬细胞结合的IgG2b比相同数量的腹腔巨噬细胞多约10倍，尽管两种类型巨噬细胞结合的结合常数（Kas）相似。计算得到的Kas值在每次实验中略有变化且随温度降低而增加，范围在1.3 - 5.3×10(8) M-1；结合位点数量估计约为10(5)/脾脏巨噬细胞和10(4)/腹腔巨噬细胞。125I-IgG2b与脾脏巨噬细胞的结合仅被IgG2b同种型的未标记蛋白抑制，而不被IgG1、IgG2a和IgG2c蛋白抑制。可溶性IgG2b - 抗原复合物也能与单体的FcR结合，但可溶性IgG2a - 抗原复合物不抑制单体IgG2b的结合。
