NEONATAL TH1/TH2 PRIMARY AND MEMORY CELL DEVELOPMENT

新生儿的免疫反应通常很差。结果，新生儿死于很少影响成年人的感染和疾病。新生儿免疫缺陷与Th1功能低下有关。由于Th1功能在细胞免疫应答中起着重要作用，因此必须清楚地了解新生儿Th1谱系细胞的失调，从而制定出预防和治疗早期疾病的策略。本研究旨在确定控制新生儿原位Th1功能低下的细胞和生化机制。具体目标1和2侧重于新生儿无法发展成熟的Th1记忆反应。特异性目的3将集中于当抗原作为佐剂递送时，新生儿不能产生增强的原发性Th1反应。特异性目的1将验证不能产生Th1显性记忆是由于新生T细胞和非T细胞发育不成熟的假设。这将通过在嵌合小鼠体内物理分离这两个区室来进行测试：将评估新生T细胞在过继的tcrβ缺陷成年宿主中发展成熟Th1记忆的能力；相反，新生儿tcrβ缺陷宿主支持成年T细胞成熟Th1记忆发育的能力将被检验。当抗原通过成熟的成年树突状细胞传递给完整的新生儿时，新生儿T细胞发展成熟Th1记忆的能力也将被研究。最后，新生儿转基因T细胞携带成熟的成人来源的TCR是否能够在正常新生儿中原位实现成熟的Th1记忆，将被测试。特异性目标2将验证一个假设，即由于内源性细胞因子环境下发育不成熟导致Th2细胞优先存活，从而导致Th1记忆不良。在初次和二次免疫后，将测量新生儿和成人中抗原特异性Th1 vs Th2细胞的频率。抗原驱动的促炎细胞因子的产生已知可调节T细胞的发育、功能和存活，将在免疫新生儿和成人中进行比较。最后，将评估外源性给予IL-2和/或促炎细胞因子影响新生儿Th1记忆发育的能力。特异性目标3将验证这样的假设：原发性Th1活性增加的新生儿对佐剂的反应失败是由于APC室的功能有限。首先，将评估新生儿T细胞和非T细胞区室的先天特性对佐剂反应性差的贡献：新生儿T细胞将被转移到tcrβ缺陷的成人宿主中，反之亦然，并且将评估佐剂中抗原的初级Th1反应。其次，将在完整新生儿和成人中比较佐剂诱导的两种主要促th1细胞因子IL-12和IL- 18的上调。最后，我们将测试联合使用IL-12和IL-18增强新生儿佐剂诱导的原发性Th1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.