As a pineal gland hormone, melatonin acts through its receptors to modulate the immune system. The immune system is composed of primary and secondary organs, and immune organs are adapted to the presence of the fetal alloantigen during pregnancy. However, it is unclear whether melatonin affects maternal immune organs during early pregnancy in sheep. In this study, the ovine thymus, lymph node, spleen and liver were sampled at day 16 of the oestrous cycle, and at days 13, 16 and 25 of pregnancy. The expression of melatonin receptor 1A (MT1), melatonin receptor 1B (MT2) and cluster of differentiation 4 (CD4) was detected by quantitative real-time polymerase chain reaction, Western blot and immunohistochemistry experiments. Our results showed that during early pregnancy there was an upregulation of MT1 mRNA and protein in the thymus, lymph node and liver, and there was a downregulation in the spleen. The expression of MT2 mRNA and protein was increased in the thymus but decreased in the spleen and liver, and there was no significant change in the lymph node during early pregnancy. CD4 protein was upregulated in the thymus, lymph node and liver, but there were no significant changes in the spleen during early pregnancy. In conclusion, early pregnancy induces tissue-specific expression of MT1, MT2 and CD4, which may be due to the different functions of the thymus, lymph node, spleen and liver. Further, melatonin is involved in immune regulation of the maternal thymus, lymph node, spleen and liver during early pregnancy in sheep.

中文翻译：

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怀孕初期绵羊胸腺，淋巴结，脾脏和肝脏中褪黑激素受体和CD4的表达。

褪黑激素作为一种松果体激素，通过其受体发挥作用来调节免疫系统。免疫系统由主要器官和次要器官组成，并且在怀孕期间免疫器官会适应胎儿同种异体抗原的存在。但是，尚不清楚褪黑激素是否会在绵羊早期妊娠期间影响母体免疫器官。在这项研究中，在雌性周期的第16天以及妊娠的第13、16和25天对绵羊的胸腺，淋巴结，脾脏和肝脏进行了采样。通过定量实时聚合酶链反应，Western印迹和免疫组化实验检测褪黑激素受体1A（MT1），褪黑激素受体1B（MT2）和分化簇4（CD4）的表达。我们的结果显示，在怀孕初期，胸腺中的MT1 mRNA和蛋白上调，淋巴结和肝脏，脾脏有下调。MT2 mRNA和蛋白的表达在胸腺中升高，但在脾脏和肝脏中降低，并且在怀孕早期的淋巴结中无明显变化。胸腺，淋巴结和肝脏中的CD4蛋白上调，但怀孕初期脾脏无明显变化。总之，早孕诱导MT1，MT2和CD4的组织特异性表达，这可能是由于胸腺，淋巴结，脾脏和肝脏的功能不同所致。此外，褪黑激素在绵羊早期妊娠期间参与了对母亲胸腺，淋巴结，脾脏和肝脏的免疫调节。MT2 mRNA和蛋白的表达在胸腺中增加，但在脾脏和肝脏中减少，并且在怀孕早期的淋巴结中无明显变化。胸腺，淋巴结和肝脏中的CD4蛋白上调，但怀孕初期脾脏无明显变化。总之，早孕诱导MT1，MT2和CD4的组织特异性表达，这可能是由于胸腺，淋巴结，脾脏和肝脏的功能不同所致。此外，褪黑激素在绵羊早期妊娠期间参与了对母亲胸腺，淋巴结，脾脏和肝脏的免疫调节。MT2 mRNA和蛋白的表达在胸腺中增加，但在脾脏和肝脏中减少，并且在怀孕早期的淋巴结中无明显变化。胸腺，淋巴结和肝脏中的CD4蛋白上调，但怀孕初期脾脏无明显变化。总之，早孕诱导MT1，MT2和CD4的组织特异性表达，这可能是由于胸腺，淋巴结，脾脏和肝脏的功能不同所致。此外，褪黑激素在绵羊早期妊娠期间参与了对母亲胸腺，淋巴结，脾脏和肝脏的免疫调节。但怀孕初期脾脏无明显变化。总之，早孕诱导MT1，MT2和CD4的组织特异性表达，这可能是由于胸腺，淋巴结，脾脏和肝脏的功能不同所致。此外，褪黑激素在绵羊早期妊娠期间参与了对孕妇胸腺，淋巴结，脾脏和肝脏的免疫调节。但怀孕初期脾脏无明显变化。总之，早孕诱导MT1，MT2和CD4的组织特异性表达，这可能是由于胸腺，淋巴结，脾脏和肝脏的功能不同所致。此外，褪黑激素在绵羊早期妊娠期间参与了对母亲胸腺，淋巴结，脾脏和肝脏的免疫调节。