Mechanisms of immune regulation by rapamycin-conditioned dendritic cells

描述（由申请人提供）：我们已经证明了异体或呈递异体抗原的未成熟树突状细胞（iDC）的能力，表达低水平的主要组织相容性复合体（MHC） II类和共刺激分子，在移植前递送时延长MHC错配的心脏移植存活。这种作用通过共刺激阻断而增强，并且iDC和共刺激阻断的结合也减少了移植血管病变。然而，没有观察到通过iDC给予的一致的无限期移植物存活，这表明注入的iDC可能容易在暴露于内源性炎症因子后成熟。我们最近的数据显示，“耐受性保留”免疫抑制药物雷帕霉素（RAPA）导致稳定未成熟的树突状细胞（RAPA- dc）通过直接和间接的异体识别途径刺激T细胞的能力明显受损，即使暴露于强炎症刺激，在没有任何免疫抑制的情况下，RAPA- dc输注在40%的动物中诱导了无限期的异体心脏移植存活。进一步的证据表明，与iDC相比，RAPA-DC有选择性地扩增Foxp3+ CD4+ CD25+ T细胞。因此，基于RAPA-DC稳定的未成熟表型及其选择性扩增Treg的倾向，联合使用共刺激阻断与RAPADC可能是一种非常有效的治疗方法，可以促进耐受性，从而减少血管硬化。因此，目前的应用将确定受体来源的RAPA-DC呈递的同种异体抗原（alloAq） Aq与CD40-CD154通路的阻断是否通过小鼠心脏移植模型中Treq的产生导致长期无排斥的同种异体存活。此外，研究的重点是阐明RAPA对DC成熟和刺激能力的抑制作用的分子机制，以及利用RAPA-DC识别对Treq细胞扩增至关重要的信号通路和qene产物。相关性：与长期使用免疫抑制剂相关的发病率，以及这些治疗方法无法防止因慢性排斥而导致的同种异体移植丢失，仍然是临床实体器官移植的重大障碍。树突状细胞是免疫反应的有效天然调节剂，如果适当地用作耐受性载体，可能是持续诱导操作耐受性的关键，减少目前对慢性免疫抑制的依赖，并阻断慢性排斥的免疫成分。

DESCRIPTION (provided by applicant): We have demonstrated the capacity of allogeneic or alloantigen-presenting immature dendritic cells (iDC), expressing low levels of major histocompatibility complex (MHC) class II and the co-stimulatory molecules, to prolong MHC-mismatched cardiac allograft survival when delivered before transplantation. This effect is potentiated by co-stimulation blockade, and the combination of iDC and co-stimulation blockade also reduced transplant vasculopathy. However, consistent indefinite graft survival via iDC administration is not observed, suggesting that infused iDC may be susceptible to maturation following exposure to endogenous inflammatory factors. Our recent data show that the 'tolerance-sparing' immunosuppressive drug rapamycin (RAPA) results in stably-immature dendritic cells (RAPA-DC) that are markedly impaired in their ability to stimulate T cells via direct and indirect pathways of allorecognition, even following exposure to potent inflammatory stimuli, RAPA-DC infusion, in the absence of any administered immunosuppression, induced indefinite cardiac allograft survival in 40% of animals. Further evidence suggests that RAPA-DC, when contrasted to iDC, selectively expand Foxp3+ CD4+ CD25+ T cells. Thus, based on the stable immature phenotype of RAPA-DC and their propensity to selectively expand Treg, the combination of co-stimulation blockade with RAPADC administration may prove a highly effective therapy to promote tolerance and thus reduce vascular sclerosis. As such, the current application will define whether alloantiqen (alloAq) Aq presentation by recipient-derived RAPA-DC in combination with blockade of the CD40-CD154 pathway results in lonq-term, rejection-free alloqraft survival through the generation of Treq in a murine heart transplant model. Also, the studies proposed are focused on elucidating the molecular mechanisms that underlie the inhibitory action of RAPA on DC maturation and stimulatory abilitv, and on utilizinq RAPA-DC to identify siqnalinq pathway and qene products that are critical for their expansion of Treq cells. Relevance: The morbidity associated with long-term immunosuppressant administration, and the failure of these treatments to prevent allograft loss due to chronic rejection, remain significant obstacles in clinical solid organ transplantation. Dendritic cells, potent natural regulators of immune responses, if properly utilized as tolerogenic vectors may hold the key to consistent induction of operational tolerance reducing the current dependence on chronic immunosuppression and blocking immunological components of chronic rejection.