Kim K M, Reth M
Max-Planck Institut für Immunbiologie, Freiburg, Germany.
J Exp Med. 1995 Mar 1;181(3):1005-14. doi: 10.1084/jem.181.3.1005.
Most mature B lymphocytes coexpress two classes of antigen receptor, immunoglobulin (Ig)M and IgD. The differences in the signal transduction from the two receptors are still a matter of controversy. We have analyzed B cell lines expressing IgM or IgD antigen receptors with the same antigen specificity. Cross-linking of these receptors with either antigen, or class-specific antibodies, results in the activation of protein tyrosine kinases and the phosphorylation of the same substrate proteins. The kinetic and the intensity of phosphorylation, however, was quite different between the two receptors when they were cross-linked by antigen. In membrane IgM-expressing cells, the substrate phosphorylation reached a maximum after 1 minute and diminished after 60 minutes whereas, in the membrane IgD-expressing cells, the substrate phosphorylation increased further over time, reached its maximum at 60 minutes, and persisted longer than 240 minutes after exposure to antigen. As a result, the intensity of protein tyrosine phosphorylation induced by cross-linking of membrane IgD was stronger than that induced by membrane IgM. Studies of chimeric receptors demonstrate that only the membrane-proximal C domain and/or the transmembrane part of membrane-bound IgD molecule is required for the long-lasting substrate phosphorylation. Together, these data suggest that the signal emission from the two receptors is controlled differently.
大多数成熟的B淋巴细胞共表达两类抗原受体，即免疫球蛋白（Ig）M和IgD。来自这两种受体的信号转导差异仍是一个有争议的问题。我们分析了表达具有相同抗原特异性的IgM或IgD抗原受体的B细胞系。用抗原或类特异性抗体使这些受体交联，会导致蛋白酪氨酸激酶的激活以及相同底物蛋白的磷酸化。然而，当通过抗原交联时，两种受体之间磷酸化的动力学和强度有很大不同。在表达膜IgM的细胞中，底物磷酸化在1分钟后达到最大值，并在60分钟后减弱；而在表达膜IgD的细胞中，底物磷酸化随时间进一步增加，在60分钟时达到最大值，并在接触抗原后持续超过240分钟。结果，膜IgD交联诱导的蛋白酪氨酸磷酸化强度比膜IgM诱导的更强。嵌合受体研究表明，持久的底物磷酸化仅需要膜结合IgD分子的膜近端C结构域和/或跨膜部分。总之，这些数据表明来自两种受体的信号发射受到不同的控制。
