IL-12 as an immunopotentiator in leishmaniasis

描述（由申请人提供）：小鼠的实验性利什曼原虫大感染已被广泛用于了解细胞介导免疫（CMI）如何发展，并明确定义决定T细胞激活后是否观察到Thl或Th2反应的因素。这些研究清楚地表明，IL-12在耐药性和Thl反应的发展中起着重要作用。然而，尽管我们对与Thl反应发展相关的事件的了解大大增加，但对控制CMI维持的规则知之甚少。我们的实验室最近表明，IL-12不仅需要启动Thl细胞的发育，而且还需要维持这种反应。这一建议旨在确定IL-12如何参与维持CMI，这样做将更广泛地研究免疫记忆如何在L. major愈合小鼠中起作用。我们的具体目标是解决CMI的三个关键组成部分：记忆T细胞功能（目标1），抗原-在这种情况下寄生虫持久性的作用（目标2），以及辅助细胞-特别是树突状细胞-既提供抗原又影响发展的T细胞的性质（目标3）。该提议的工作假设是，CMI需要从非极化的T细胞池中不断更新Thl种群。为了验证这一假设，提出了一系列过继转移实验，包括传统T细胞，以及识别利什曼抗原的TCR转基因T细胞。将在受体小鼠中跟踪供体细胞，以评估它们的运输模式、细胞因子的产生和寿命。分析寄生虫持久性的作用将使用一种L. major （dhfr-ts-）胸腺嘧啶缺陷细胞感染小鼠，但不能存活。最后，抗原呈递的作用将通过表征与耐药性相关的树突状细胞反应来评估。该实验室的初步研究表明，CD40-CD40L相互作用不是维持免疫所必需的，为此，将测试TRANCE的代偿作用。总的来说，这些实验应该提供T细胞、树突状细胞和持续寄生虫之间动态相互作用的清晰图像，这些相互作用是维持细胞介导免疫所必需的。

DESCRIPTION (provided by the applicant): Experimental Leishmania major infections in mice have been used extensively to understand how cell-mediated immunity (CMI) develops, and to specifically define the factors that dictate whether a Thl or Th2 response is observed after activation of T cells. Such studies have clearly shown an important role for IL-12 in the development of resistance and a Thl response. However, despite a great increase in our knowledge of the events that are associated with the development of Thl responses, little is understood about the rules that govern the maintenance of CMI. Our laboratory has recently shown that IL-12 is required not only to initiate Thl cell development, but also to maintain this response. This proposal seeks to determine how IL-12 participates in maintaining CMI, and in so doing will more broadly investigate how immunologic memory works in L. major healed mice. Our specific aims address the three critical components for CMI: memory T cell function (Aim 1), the antigen-in this case the role of parasite persistence (Aim 2), and the accessory cells-specifically dendritic cells-that both present antigen and influence the nature of the T cells that develop (Aim 3). The working hypothesis of this proposal is that CMI requires the constant renewal of the Thl population from a non-polarized pool of T cells. To test this hypothesis a series of adoptive transfer experiments are proposed, both with conventional T cells, as well as TCR transgenic T cells recognizing a leishmanial antigen. The donor cells will be followed in the recipient mice to assess their trafficking patterns, cytokine production and life span. An analysis of the role of parasite persistence will use a L. major (dhfr-ts-) thymidine auxotroph that infects mice, but fails to survive. Finally, the role of antigen presentation will be assessed by characterizing the dendritic cell response associated with resistance. Preliminary studies from this laboratory demonstrated that CD40-CD40L interactions are not required for maintenance of immunity, and in this aim, the compensatory role of TRANCE will be tested. Overall, these experiments should provide a clear picture of the dynamic interactions between T cells, dendritic cells and persisting parasites that are required to maintain cell-mediated immunity.