Molecular events in the generation of memory B cells.

我们以前观察到Fas介导的信号调节记忆B细胞的产生，在晚期免疫应答中，记忆B细胞在V_H基因中大量积累体细胞突变。为了检查Fas在记忆B细胞的持久性中的作用，从NP-致敏的C57 BL/6或C57 BL/6-lpr/lpr小鼠中纯化记忆B细胞，并转移到载体致敏的小鼠中，然后在细胞转移后的不同时间间隔使用可溶性NP-载体蛋白进行攻击。结果表明，当转移的细胞在受体中放置3周时，NP致敏的记忆细胞不引起二次应答，而NP致敏的lpr记忆细胞在相同条件下对二次攻击有应答。在转移正常的NP-致敏的B细胞后立即将抗Fas单克隆抗体给予受体，导致在转移后3周通过激发产生次级应答。这些结果表明Fas介导的信号负调控记忆的持续性，尽管已知负责GC形成的几种分子的缺陷减少了高亲和力记忆B细胞的产生，但在GC形成后记忆B细胞产生的机制仍然很大程度上未知。为了研究ras在记忆B细胞发育中的作用，我们分析了C57 BL/6小鼠的B细胞反应，这些小鼠在其B系细胞中以高水平表达显性阴性ras。ras活性的抑制降低了脾脏中高亲和力记忆细胞的频率，并损害了记忆B细胞对次级应答的活性。然而，Ras活性的抑制并不影响血清抗体，GC形成，体细胞突变和高亲和力GC和抗体形成细胞的选择的主要反应。这些结果表明ras选择性参与记忆B细胞的建立。

We have previously observed that a Fas-mediated signal regulated the generation of memory B cells which heavily accumulated somatic mutations in the V_H gene at the late immune response. To examine the role of Fas in the persistence of memory B cells, memory B cells were purified from NP-primed C57BL/6 or C57BL/6-lpr/lpr mice and transferred into carrier-primed mice, followed by a challenge using a soluble NP-carrier protein administered at different intervals after cell-transfer. The result shows that NP-primed memory cells did not elicit a secondary response when transferred cells were left in the recipient for 3wks, however, NP-primed lpr memory cells responded to the secondary challenge at the same condition. Administration of anti-Fas mAbs into the recipient immediately after the transfer of normal NP-primed B cells resulted in the generation of a secondary response by challenge 3wks after the transfer. These results suggest that the Fas mediated signal negatively regulates memory persistence.Although it is known that a deficiency in several molecules responsible for GC-formation reduces the generation of high-affinity memory B cells, the mechanism for the generation of memory B cells at the post GC-formation remains largely unknown. To examine the role of ras in memory B cell development, we have analyzed the B cell response in C57BL/6 mice who express dominant-negative ras at high levels in their B-lineage cells. Inhibition of ras activity reduced the frequency of high affinity memory cells in the spleen and impaired memory B cell activity for the secondary response. However, inhibition of Ras activity did not affect the primary response by serum antibodies, GC-formation, somatic mutations and selection of high-affinity GC and antibody-forming cells. These results suggest that ras is selectively involved in the establishment of memory B cells.