Gilman-Sachs A, Dray S
Mol Immunol. 1985 Jan;22(1):57-65. doi: 10.1016/0161-5890(85)90034-3.
IgM from trypanosome-infected rabbits was digested with trypsin under different conditions to obtain Fab mu or Fc5 mu fragments suitable for analysis with anti-allotype and anti-isotype antibodies. The Fab mu but not the Fc5 mu fragment was shown to have the n-locus allotypic specificities, n80, n81, n82, n83 and n87, characteristic of the IgM class of immunoglobulins. Thus, the n82 and n83 allotypic specificities, conformationally dependent on the a VH locus for expression, and the n80, n81 and n87 allotypic specificities, independent of the a VH locus for expression, are in either the CH1 or CH2 domain of IgM heavy chains. In addition, two high-affinity mouse monoclonal antibodies (MoAbs) specific for IgM and able to bind IgM in direct-binding radioimmunoassays were produced and characterized. One MoAb (3C1) was specific for an isotypic determinant (epitope) in the Fab mu fragment, presumably in the CH1 or CH2 domain, whereas another MoAb (8C2) was specific for an isotypic epitope in the Fc5 mu fragment, presumably in the CH3 or CH4 domain. The proximity of the n-locus allotypic specificities (CH1 or CH2 domain) to the VH domain is consistent with the finding that some IgM allotypic specificities are expressed only in conjunction with certain a VH locus allotypic specificities.
用胰蛋白酶在不同条件下消化来自锥虫感染兔子的IgM，以获得适用于用抗同种异型和抗同种型抗体进行分析的Fabμ或Fc5μ片段。结果显示，Fabμ片段而非Fc5μ片段具有免疫球蛋白IgM类特有的n位点同种异型特异性n80、n81、n82、n83和n87。因此，构象上依赖于αVH位点表达的n82和n83同种异型特异性，以及不依赖于αVH位点表达的n80、n81和n87同种异型特异性，位于IgM重链的CH1或CH2结构域中。此外，制备并表征了两种对IgM具有特异性且能够在直接结合放射免疫分析中结合IgM的高亲和力小鼠单克隆抗体（MoAb）。一种MoAb（3C1）对Fabμ片段中的同种型决定簇（表位）具有特异性，可能位于CH1或CH2结构域，而另一种MoAb（8C2）对Fc5μ片段中的同种型表位具有特异性，可能位于CH3或CH4结构域。n位点同种异型特异性（CH1或CH2结构域）与VH结构域的接近性与某些IgM同种异型特异性仅与某些αVH位点同种异型特异性共同表达的发现一致。
