van Oss C J, Absolom D R, Michaeli J
Immunol Invest. 1985 Apr;14(2):167-76. doi: 10.3109/08820138509042011.
The binding constant of Fc-moieties of IgG and their receptors (R), derived via the law of mass action, yields values that are of the order of 10(6) to 10(8) L/M. In circulating blood, phagocytic R must be bound rather strongly to IgG, which is normally present in high concentrations, so that it is unlikely that Fc-R mediated interactions between rather sparse sensitized particles and phagocytes take place to any significant degree in the blood stream. However, in the spleen, where Fc-R mediated interactions do play a more important role, the situation is different, due to: a) an increased cell concentration; b) a decreased relative IgG concentration; c) a locally very high macrophage concentration, with large numbers of R per cell. It can be shown that these changed conditions in the spleen cause a shift in the equilibrium of the Fc-R interaction in favor of sensitized particle Fc-R binding, with diminished involvement of freely circulating IgG. The law of mass action can also be used to predict the degree of washing of phagocytic cells needed to remove bound immunoglobulin. Conversely, measurement of the concentrations of free and bound immunoglobulin at different dilutions allows the determination of Ka as well as of the number of R per cell.
通过质量作用定律得出的IgG的Fc部分与其受体（R）的结合常数，其值在10⁶至10⁸L/M的数量级。在循环血液中，吞噬细胞受体必须与通常以高浓度存在的IgG紧密结合，因此在血流中，稀疏的致敏颗粒与吞噬细胞之间由Fc受体介导的相互作用不太可能在任何显著程度上发生。然而，在脾脏中，Fc受体介导的相互作用确实发挥着更重要的作用，这是由于：a）细胞浓度增加；b）相对IgG浓度降低；c）局部巨噬细胞浓度非常高，每个细胞有大量的受体。可以证明，脾脏中这些变化的条件导致Fc受体相互作用的平衡向有利于致敏颗粒与Fc受体结合的方向移动，而游离循环IgG的参与减少。质量作用定律还可用于预测去除结合的免疫球蛋白所需的吞噬细胞洗涤程度。相反，测量不同稀释度下游离和结合免疫球蛋白的浓度，可以确定Ka以及每个细胞的受体数量。
