NEONATAL TH1/TH2 PRIMARY AND MEMORY CELL DEVELOPMENT

新生儿的免疫反应往往很差。 因此，新生儿容易感染成年人很少感染的疾病。 新生儿的免疫缺陷与Th 1功能低下有关。 由于Th 1功能在细胞免疫应答中至关重要，因此必须清楚地了解新生儿Th 1谱系细胞的失调，以制定导致早期疾病预防和治疗的策略。 这项建议的目的是确定的细胞和生化机制，在新生儿原位Th 1功能差。 具体目标1和2关注新生儿不能发展成熟的Th 1记忆应答。具体目标3将集中于当抗原在佐剂中递送时新生儿不能产生增强的初级Th 1应答。 具体目标1将检验不能产生Th 1显性记忆是由于新生儿T细胞和非T细胞发育不成熟的假设。 这将通过在体内物理分离嵌合小鼠中的两个隔室来测试：将评估新生儿T细胞在过继性成年TCR β缺陷型宿主中形成成熟Th 1记忆的能力;相反，将检查新生儿TCR β缺陷型宿主支持成年T细胞形成成熟Th 1记忆的能力。 还将研究当抗原通过成熟成人树突细胞递送至完整新生儿时新生儿T细胞发展成熟Th 1记忆的能力。 最后，将测试携带成熟的成人来源的TCR的新生儿转基因T细胞是否能够在过继转移的正常新生儿中原位实现成熟的Th 1记忆。 具体目标2将检验以下假设：Th 1记忆差是由于内源性细胞因子环境中发育不成熟导致Th 2细胞优先存活所致。 在初次和二次免疫后，将测量新生儿和成人中抗原特异性Th 1与Th 2细胞的频率。 将在免疫的新生儿和成人中比较已知调节T细胞发育、功能和存活的促炎细胞因子的抗原驱动的产生。最后，将评估外源施用的IL-2和/或促炎细胞因子影响新生儿中Th 1记忆发育的能力。 具体目标3将检验以下假设：新生儿对具有增加的初级Th 1活性的佐剂应答失败是由于APC隔室内的功能有限。首先，将评估新生儿T细胞和非T细胞区室的先天性质对佐剂应答性差的贡献：将新生儿T细胞转移至成年TCR β缺陷型宿主，反之亦然，并将评估对佐剂中抗原的初级Th 1应答。 其次，将在完整的新生儿和成人中比较促Th 1细胞因子IL-12和IL- 18的促Th 1细胞因子的促 最后，将测试共同施用的IL-12和IL-18增强新生儿中佐剂诱导的初级Th 1功能的能力。

Immune responses in neonates are often poor. As a result, neonates succumb to infections and diseases which seldom affect adults. The deficient immunity of neonates is associated with poor Th1 function. Because Th1 function is centrally important in cellular immune responses, a clear understanding of the dysregulation of Th1 lineage cells in neonates must be achieved to devise strategies leading to the prevention and treatment of disease in early life. This proposal aims to identify the cellular and biochemical mechanisms governing poor Th1 function in neonates in situ. Specific Aims 1 and 2 focus on the inability of neonates to develop mature Th1 memory responses. Specific Aim 3 will concentrate on the failure of neonates to generate enhanced primary Th1 responses when antigen is delivered in adjuvant. Specific Aim 1 will test the hypothesis that the inability to generate Th1 dominant memory is due to developmental immaturity in both neonatal T cells and non-T cells. This will be tested by physically separating the two compartments in chimeric mice in vivo: the capacity of neonatal T cells to develop mature Th1 memory in adoptive adult TCRbeta-deficient hosts will be assessed; conversely, the capacity of neonatal TCRbeta-deficient hosts to support mature Th1 memory development by adult T cells will be examined. The ability of neonatal T cells to develop mature Th1 memory when antigen is delivered to intact neonates by mature adult dendritic cells will also be investigated. Lastly, whether neonatal transgenic T cells bearing mature, adult-derived TCR are able to achieve mature Th1 memory in situ, in adoptively transferred normal neonates, will be tested. Specific Aim 2 will test the hypothesis that poor Th1 memory results from the preferential survival of Th2 cells due to developmental immaturity in the endogenous cytokine milieu. The frequencies of antigen-specific Th1 vs Th2 cells in neonates and adults will be measured following primary and secondary immunization. The antigen-driven production of proinflammatory cytokines known to modulate T cell development, function, and survival will be compared in immunized neonates and adults. Lastly, the capacity of exogenously administered IL-2 and/or proinflammatory cytokines to influence Th1 memory development in neonates will be assessed. Specific Aim 3 will test the hypothesis that the failure of neonates to respond to adjuvant with increased primary Th1 activity is due to limited function within the APC compartment. First, the contributions of the innate properties of the neonatal T cell and non-T cell compartments to poor responsiveness to adjuvant will be assessed: neonatal T cells will be transferred to adult TCRbeta-deficient hosts, and vice versa, and primary Th1 responses to antigen in adjuvant will be assessed. Second, the adjuvant-induced upregulation of two major Th1-promoting cytokines, IL-12 and IL- 18, will be compared in intact neonates and adults. Finally, the capacity of coadministered IL-12 and IL-18 to enhance adjuvant- induced primary Th1 function in neonates will be tested.