Somatic hypermutation and rescue from self-reactivity in Pre-B lymphocytes

项目摘要 B细胞受体多样性的产生是由RAG重组酶介导的，并且它发生在细胞周期中。 骨髓中的B细胞发育。这是由随机重排带来的， V（D）J基因片段组装B细胞受体。这些随机重排也 导致识别自身抗原的B细胞的发育。这些自身反应性B细胞克隆 通过克隆缺失、克隆无反应性或RAG重组酶介导的对 通过V基因片段置换获得自反应克隆。在本提案中，我们提出了一个额外的 自身反应性前B细胞从自身反应性中拯救出来的机制。我们建议 激活诱导的胞苷脱氨酶（AID）在拯救自身反应性前B细胞中起作用。 AID诱导抗原激活的成熟B细胞中两个显著的遗传改变;体细胞 超突变和类切换重组。前者产生高亲和力的B细胞突变体 而后者促进了IG同种型从IgM IgG、伊加或IgE。 有趣的是，二十多年来人们已经知道，一小部分未成熟的骨骼， 骨髓前B细胞经历类别转换。这是令人困惑的，因为它甚至发生在前B 仅重排其IG重链而尚未重排其轻链的细胞。 我们，基于非常初步的数据，可能有一个答案，这个谜。我们的核心假设 是不成熟的，自我反应的前B细胞开启AID并经历体细胞突变， 将它们的特异性从自身反应性改变为非自身反应性。在这些骨骼中发生的类转换 骨髓前B细胞是AID表达的附带结果。我们将测试我们的中央 假设有两个目标。这项拟议的工作意义重大，因为一旦完成，我们将有 建立了一个新的范式来解释前B细胞从自身反应性中的拯救。我们很好- 作为我们的团队，我们有能力开展拟议的研究，并增加了合作者Dr. 伊格纳西奥桑兹是世界上首屈一指的自身免疫专家之一， 专业知识，以成功完成拟议的研究。

PROJECT SUMMARY The generation of B cell receptor diversity is mediated by RAG recombinases, and it occurs during B cell development in the bone marrow. This is brought about by stochastic rearrangement of V(D)J gene segments to assemble the B cell receptor. These stochastic rearrangements also lead to the development of B cells that recognize self-antigens. These self-reactive B cell clones are dealt with by either clonal deletion, clonal anergy or RAG recombinase-mediated rescue of self-reactive clones by V gene segment replacement. In this proposal, we present an additional mechanism by which autoreactive pre-B cells are rescued from self-reactivity. We propose that Activation-induced Cytidine Deaminase (AID) plays a role in rescuing self-reactive pre-B cells. AID induces two significant genetic alterations in antigen-activated mature B cells; somatic hypermutation and class switch recombination. The former generates high-affinity B cell mutants that are enticed to enter the memory pool, and the latter facilitates Ig isotype switching from IgM to IgG, IgA or IgE. Interestingly, it has been known for over two decades that a small fraction of immature, bone marrow pre-B cells undergo class switching. This is perplexing because it occurs even in pre-B cells which have only rearranged their Ig heavy chain and are yet to rearrange their light chains. We, based on very preliminary data may have an answer to this puzzle. Our central hypothesis is that immature, self-reactive pre-B cells turn on AID and undergo somatic mutation in order to alter their specificity from self- to non-self-reactivity. The class switching that occurs in these bone marrow pre-B cells is a collateral consequence of AID expression. We will test our central hypothesis in two aims. The proposed work is significant because, upon completion, we will have established a new paradigm to explain the rescue of pre-B cells from self-reactivity. We are well- positioned to carry out the proposed studies as our team with the addition of collaborator Dr. Ignacio Sanz, one of the world’s premier experts on autoimmunity, has the requisite collective expertise to complete the proposed studies successfully.