Zimmermann V S, Rovere P, Trucy J, Serre K, Machy P, Forquet F, Leserman L, Davoust J
Centre d'Immunologie, Centre National de la Recherche Scientifique-Institut National de la Santé et de la Recherche Médicale de Marseille-Luminy, Marseille, France.
J Immunol. 1999 Mar 1;162(5):2495-502.
The intracellular sites in which Ags delivered by the B cell receptor (BCR) are degraded and loaded onto class II molecules remain poorly defined. To address this issue, we generated wild-type and invariant chain (Ii)-deficient H-2k mice bearing BCR specific for hen egg lysozyme. Our results show that, 1) unlike Ags taken up from the fluid phase, Ii is required for presentation of hen egg lysozyme internalized through the BCR in a manner independent of the peptide analyzed; 2) BCR ligation induces intracellular accumulation of MHC class II molecules only in Ii-positive B cells; and 3) these class II molecules reach intracellular compartments where BCR targets exogenous Ag. No differences in expression of adhesion and costimulatory molecules or in the presentation of soluble peptides were detectable between Ii-positive and -negative B cells. Therefore, the BCR delivers its ligand to compartments containing MHC class II-Ii complexes and bypasses the Ii-independent presentation pathway. The linked roles of Ag internalization and B cell activation of the BCR leads to potent Ii-dependent presentation in splenic B cells.
B细胞受体（BCR）传递的抗原在细胞内被降解并加载到II类分子上的具体位点仍不清楚。为了解决这个问题，我们构建了携带针对鸡卵溶菌酶的BCR的野生型和恒定链（Ii）缺陷型H-2k小鼠。我们的结果表明，1）与从液相摄取的抗原不同，Ii对于以与所分析肽无关的方式通过BCR内化的鸡卵溶菌酶的呈递是必需的；2）BCR连接仅在Ii阳性B细胞中诱导MHC II类分子的细胞内积累；3）这些II类分子到达BCR靶向外源抗原的细胞内区室。在Ii阳性和阴性B细胞之间，未检测到粘附分子和共刺激分子表达或可溶性肽呈递的差异。因此，BCR将其配体传递到含有MHC II-Ii复合物的区室，并绕过不依赖Ii的呈递途径。抗原内化和BCR的B细胞活化的相关作用导致脾脏B细胞中有效的Ii依赖性呈递。
