NEONATAL TH1/TH2 PRIMARY AND MEMORY CELL DEVELOPMENT

新生儿的免疫反应往往很差。因此，新生儿会死于感染和疾病，而这些感染和疾病很少影响成年人。新生儿免疫功能低下与Th1功能低下有关。由于Th1功能在细胞免疫反应中起核心作用，因此必须清楚地了解新生儿Th1系细胞的失调，以制定策略，从而在生命早期预防和治疗疾病。这项建议旨在确定原位新生儿Th1功能低下的细胞和生化机制。具体目标1和2侧重于新生儿不能发展成熟的Th1记忆反应。具体目标3将集中在新生儿在将抗原输送到佐剂中时未能产生增强的初级Th1反应。具体目标1将检验这一假设，即无法产生Th1优势记忆是由于新生儿T细胞和非T细胞的发育不成熟所致。这将通过在体内通过物理分离嵌合小鼠的两个隔室来进行测试：将评估收养的成年TCRbeta缺陷宿主中新生T细胞发展成熟Th1记忆的能力；反过来，将检测新生TCRbeta缺陷宿主支持成年T细胞成熟Th1记忆发展的能力。当成熟的成人树突状细胞将抗原传递给完整的新生儿时，新生儿T细胞发展成熟的Th1记忆的能力也将被研究。最后，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实现成熟的Th1记忆，将进行测试。特定目的2将检验Th1记忆不良的假设，即Th2细胞由于发育不成熟而在内源性细胞因子环境中优先存活。在初次免疫和二次免疫后，将测量新生儿和成人中抗原特异性Th1和Th2细胞的频率。抗原驱动的促炎细胞因子的产生已知调节T细胞的发育、功能和存活，将在免疫的新生儿和成人中进行比较。最后，将评估外源性应用IL-2和/或促炎细胞因子影响新生儿Th1记忆发育的能力。具体目标3将检验这样一种假设，即新生儿对初级Th1活性增加的佐剂反应失败是由于APC隔室内的功能受限。首先，将评估新生儿T细胞和非T细胞区段的先天特性对佐剂反应不良的贡献：新生儿T细胞将被转移到成人TCRbeta缺陷宿主，反之亦然，并将评估初始Th1对佐剂中的抗原的反应。其次，在完整的新生儿和成人中，将比较佐剂诱导的两种主要的Th1促进细胞因子IL-12和IL-18的上调。最后，将测试联合应用IL-12和IL-18增强新生儿佐剂诱导的初级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.