Ontogeny of Immunity in Frogs/Thyroid Hormone Effects

先前关于蝌蚪和哺乳动物的免疫反应的研究 成年南非爪蛙，非洲爪蟾，已经表明， 蝌蚪的反应通常较差，表明未成熟的 免疫系统 因为免疫反应在 变态，这种改善似乎是甲状腺素 依赖性，据推测，激素的变化， 变态将幼虫的免疫系统转变为成虫 类型系统 具体而言，建议人口 幼虫淋巴细胞在变态时被破坏， 在另一个种群的新一轮造血之后， 将在成人中发挥作用。 这里提出的研究是 旨在进一步检查免疫缺陷， 由于发育期间甲状腺激素浓度低而导致 和变形，以更清楚地确定是否有一个独特的 幼虫淋巴细胞群存在，并检查影响 在变态过程中甲状腺激素浓度的改变 关于假定的幼虫种群的下降和 成年人口。 甲状腺的直接影响， 皮质类固醇激素对培养的 变态前蝌蚪的淋巴细胞，变态 蝌蚪和成年青蛙也将被研究。 最后，一项研究 I类MHC抗原的表达， 变态青蛙将测试一个假设， 这些青蛙的同种异体移植排斥反应是由于过早的 表达前成人淋巴细胞群的扩增 I类抗原。 因为蝌蚪是作为自由生活的有机体发育的， 需要一个功能性的免疫系统来保护他们免受 环境病原体 幼虫的免疫系统必须改变 在适应新的成虫特异性抗原的变态过程中， 或者这些抗原会被识别为外来的， 变态蝌蚪会开始自我毁灭。 了解免疫系统在变态时的变化， 各种变态相关激素在这些中的作用 这些变化应该让我们更深入地了解 自我识别和免疫耐受以促进自我发展。

Previous studies of the immune responses of tadpoles and adult South African clawed frogs, Xenopus laevis, have shown that tadpole responses are generally poorer, indicative of an immature immune system. Because immune responses improve after metamorphosis, and this improvement appears to be thyroxine dependent, it is postulated that the hormonal changes at metamorphosis transform the larval immune system to an adult- type system. Specifically, it is proposed that a population of larval lymphocytes is destroyed at metamorphosis and is replaced following a new wave of hematopoiesis by another population that will function in the adult. The studies proposed here are designed to examine further the immunological deficits that result from low thyroid hormone concentrations during development and metamorphosis, to establish more clearly whether a distinct larval lymphocyte population exists, and to examine the effects of altered thyroid hormone concentrations during metamorphosis on the decline of the putative larval population and emergence of the adult population. Direct effects of thyroid and corticosteroid hormones on the viability and function of cultured lymphocytes from premetamorphic tadpoles, metamorphosing tadpoles, and adult frogs will also be studied. Finally, a study of the expression of Class I MHC antigens in precociously metamorphosis frogs will test the hypothesis that altered skin allograft rejection responses in these frogs is due to premature expansion of the adult lymphocyte population prior to expression of Class I antigens. Because tadpoles develop as free-living organisms they need a functional immune system to protect them from environmental pathogens. The larval immune system must change during metamorphosis to accomodate new adult-specific antigens, or these antigens would be recognized as foreign and the metamorphosing tadpole would begin to destroy itself. Understanding how the immune system changes at metamorphosis and the role of various metamorphosis-related hormones in these changes should give us greater insight into the process by which self-recognition and immunological tolerance to self develop.