Transcriptional Control of Memory Responses to Red Blood Cell Alloimmunization

描述(申请人提供)：红细胞同种异体免疫仍然是输血医学中常见的临床问题。同种异体抗体导致溶血性输血反应，导致大量发病率和偶尔死亡。对于那些不幸制造出多种同种异体抗体的患者，提供相容的红细胞可能既耗费时间又耗费资源。在某些情况下，这可能导致无法找到原本可以挽救生命的疗法。尽管它们在临床上很重要，但我们对RBC输血的弱刺激如何产生长寿记忆RBC同种抗体反应的了解仍然有限。鉴于记忆淋巴细胞共享通常为干细胞保留的功能属性，如自我平衡自我更新，我们和其他人假设它们重新激活了部分造血干细胞遗传程序。为了支持这一观点，我们发表了记忆B细胞、记忆CD8+T细胞和造血干细胞共有的共同转录特征。我们进一步证明，相对于寿命较短的细胞，转录因子Pou6f1在记忆B和CD8+T细胞中选择性上调。Pou6f1是POU结构域转录因子家族的成员，是Pou5f1(又名Oct4)的同源基因。Oct4作为胚胎干细胞自我更新的主要调节因子之一，建立了一个稳定的、自我强化的遗传回路，指导自我更新基因的活跃转录，同时保持分化的特定转录因子处于关闭但稳定的状态。我们认为Pou6f1在记忆T和B细胞中的功能类似于胚胎干细胞中的Oct4。中心假设是Pou6f1引导记忆抗体对红细胞同种异体免疫的反应。这一假设导致了一系列预测，我们将在一系列遗传和生化实验中测试我们最近用k和HOD红细胞同种免疫模型产生的Pou6f1牙线小鼠。目的1是验证Pou6f1在T和B细胞中的表达是产生长期、可增强的红细胞同种抗体反应所必需的预测。目的2是为了验证Pou6f1在记忆T和B淋巴细胞中的持续表达是维持对RBC同种免疫的回忆反应所必需的，以及Pou6f1是维持抗原特异性记忆淋巴细胞对动态平衡细胞因子信号的反应性所必需的。随着时间的推移，我们预计，识别驱动RBC抗体产生的分子回路将为进一步的临床开发提供治疗和诊断靶点。

DESCRIPTION (provided by applicant): RBC alloimmunization remains a common clinical problem in transfusion medicine. Alloantibodies are responsible for hemolytic transfusion reactions; leading to substantial morbidity and occasional mortality. For those patients unfortunate enough to make multiple alloantibodies, provision of compatible RBCs can be both time and resource intensive. In some cases, this can result in an inability to locate an otherwise life-saving therapy. Despite their clinical importance, our understanding of how long-lived memory RBC alloantibody responses are generated by the weak stimulus of RBC transfusion remains limited. Given that memory lymphocytes share functional attributes typically reserved for stem cells such as homeostatic self-renewal, we and others have hypothesized that they have reactivated a portion of the hematopoietic stem cell genetic program. In support of this idea, we published a common transcriptional signature shared between memory B cells, memory CD8+ T cells and hematopoietic stem cell. We have gone on to show that the transcription factor Pou6f1 is selectively upregulated in memory B and CD8+ T cells relative to shorter-lived cells. Pou6f1 is a member of the Pou-domain family of transcription factors and is a paralog of Pou5f1 (aka Oct4). Oct4 serves as one of the master regulators of embryonic stem cell self-renewal; establishing a stable, self-reinforcing genetic circuit that directs active transcription of self-renewal genes while maintaining differentiation specific transcription factor in an off, but poised state. We believe Pou6f1 functions in memory T and B cells in a manner similar to Oct4 in embryonic stem cells. The central hypothesis is that Pou6f1 directs memory antibody responses to RBC alloimmunization. This hypothesis leads to a set of predictions that we will test in vivo in a series of genetic and biochemical experiments combining Pou6f1 floxed mice we have recently generated with both the k and HOD RBC alloimmunization models. Aim 1 is to test the prediction that Pou6f1 expression in both T and B cells is required for the generation of long-lived, boostable RBC alloantibody responses. Aim 2 is to test the prediction that continued Pou6f1 expression in memory T and B lymphocytes is required to maintain recall responses to RBC alloimmunization, and that Pou6f1 is required to maintain responsiveness of antigen specific memory lymphocytes to homeostatic cytokine signals. In the fullness of time, we anticipate that identification of the molecular circuitry driving RBC antibody production will provide therapeutic and diagnostic targets for further clinical development.