Populations of Yangtze finless porpoises (YFPs) have rapidly declined in recent decades, raising the specter of extinction. In order to protect YFPs, a greater understanding of their biology is needed, including studying how their immune functioning changes with age. Here, we systematically studied the hematologic and biochemical parameters, as well as mRNAs and miRNAs profiles of old, adult, and young YFPs. The lymphocyte (LYMPH), neutrophils (NEUT) and eosinophils (EOS) counts in old YFPs were lower than those in young or adult YFPs. When comparing old to adult YFPs, the latter showed higher expression of genes associated with the innate and adaptive immune systems, including complement components, major histocompatibility complex, interleukins, TNF receptors, and chemokines/cytokines. When comparing old to young YFPs, the most striking difference was in higher toll-like receptor signaling in the latter. When comparing adult to young YFPs, the former exhibited higher expression of genes related to adaptive immunity and the FoxO signaling pathway, but lower expression of genes associated with the PI3K-Akt signaling pathway. Negative miRNA-mRNA interactions were predicted in comparisons of the old and adult (326), old and young (316), adult and young (211) groups. Overall, these results delineate a progression from early innate immune function dominance to adaptive immune function enhancement (young to adult) and deterioration (adult to old), and the changes in miRNAs profile correlate with the effects of age on immune functions. This study is the first to observe the changes of immune function of Yangtze finless porpoise with age using transcriptome method, and the study's findings are of great significance for protecting this endangered species.

近几十年来，长江江豚（YFP）的数量迅速下降，引发了灭绝的危险。为了保护 YFP，需要更深入地了解它们的生物学，包括研究它们的免疫功能如何随年龄变化。在这里，我们系统地研究了血液学和生化参数，以及老年、成人和年轻 YFP 的 mRNA 和 miRNA 谱。老年 YFP 的淋巴细胞 (LYMPH)、中性粒细胞 (NEUT) 和嗜酸性粒细胞 (EOS) 计数低于年轻或成人 YFP。当比较老年和成人 YFP 时，后者显示出与先天性和适应性免疫系统相关的基因的更高表达，包括补体成分、主要组织相容性复合物、白细胞介素、TNF 受体和趋化因子/细胞因子。在比较年长和年轻的 YFP 时，最显着的差异是后者中更高的 Toll 样受体信号传导。当比较成年和年轻的 YFP 时，前者表现出与适应性免疫和 FoxO 信号通路相关的基因表达较高，但与 PI3K-Akt 信号通路相关的基因表达较低。在老年人和成人 (326)、老年人和年轻人 (316)、成人和年轻人 (211) 组的比较中预测了负 miRNA-mRNA 相互作用。总体而言，这些结果描绘了从早期先天免疫功能优势到适应性免疫功能增强（年轻到成人）和退化（成人到老年）的过程，并且 miRNA 谱的变化与年龄对免疫功能的影响相关。本研究首次采用转录组方法观察长江江豚免疫功能随年龄的变化，