Circolo A, Borsos T
J Immunol. 1982 Oct;129(4):1485-8.
It has been known for many years that IgG-C4 complexes are generated during the activation of the classical complement pathway. Information regarding binding of C4 by IgM is not available. We studied the binding of human C4 by natural human and rabbit anti-hapten IgM under conditions in which the IgM was bound to hapten coupled to sheep red cells. We eluted the IgM by excess fluid phase hapten, reattached the eluted IgM to red cells coupled with hapten, and transferred the IgM from red cell-IgM-C4 complexes to red cells coupled with hapten. Analysis of the cells by radioimmunoassay and/or by hemolytic assays showed that no C4 was eluted from the cells with the IgM, that no C4 transferred from cell to cell with the IgM, and that the C4 remaining on the cells was hemolytically active. We concluded that in contrast to IgG, natural human and rabbit IgM at a cell surface failed to bind C4.
多年来人们已经知道，在经典补体途径激活过程中会产生IgG-C4复合物。关于IgM与C4结合的信息尚无定论。我们研究了在IgM与偶联到绵羊红细胞上的半抗原结合的条件下，天然人源和兔抗半抗原IgM与人C4的结合情况。我们用过量的液相半抗原洗脱IgM，将洗脱的IgM重新附着到偶联有半抗原的红细胞上，并将IgM从红细胞-IgM-C4复合物转移到偶联有半抗原的红细胞上。通过放射免疫测定和/或溶血测定对细胞进行分析表明，没有C4与IgM一起从细胞上洗脱下来，没有C4随IgM从一个细胞转移到另一个细胞，并且留在细胞上的C4具有溶血活性。我们得出结论，与IgG不同，细胞表面的天然人源和兔IgM不能结合C4。
