H5ad_file

The cellular components and defense mechanisms of innate immunity have diversified alongside the evolution from invertebrates to vertebrates to adapt to a rapidly changing environment. It remains unclear how immune functions and corresponding molecules are conserved or have diverged during evolution. Here, we generated invertebrate hemolymph and vertebrate blood single cell transcriptome landscapes across six species at different taxonomic nodes and combined them with public data to construct a comprehensive cross-species cellular hierarchy. We defined distinctive phagocytic-like cells (PLCs) within various invertebrates that share homologous transcriptional programs with vertebrate myeloid cells. Through cross-species comparisons, we identified a variety of functional molecules and transcription factors shared by phagocytic cells in invertebrates and myeloid cells in vertebrates, which are the core regulatory programs for the inheritance of phagocytic capabilities. Remarkably, we combined the latest Stereo-Cell technology to define specific hemocyte subtypes in invertebrates as potential ancestors of thrombocytes through the expression of coagulation-related factors in clots. Our study elucidates the ancient and conserved aspects of phagocytosis in immune system evolution and provides the first specific definition for the origin of thrombocytes.

先天免疫的细胞组分与防御机制，随无脊椎动物向脊椎动物的演化历程不断发生分化，以适应快速变化的环境。目前学界尚未明确，免疫功能及其对应分子在演化过程中是如何得以保守保留或是发生分化的。本研究针对六个处于不同分类学节点的物种，生成了无脊椎动物血淋巴与脊椎动物血液的单细胞转录组图谱，并结合公共数据构建了一套全面的跨物种细胞层级图谱。我们在多种无脊椎动物中鉴定出一类独特的类吞噬细胞（PLCs），该类细胞与脊椎动物髓系细胞共享同源转录调控程序。通过跨物种比对分析，我们鉴定出无脊椎动物吞噬细胞与脊椎动物髓系细胞共有的多种功能分子与转录因子，这些分子构成了吞噬能力遗传的核心调控程序。值得注意的是，我们结合最新的Stereo-Cell技术（Stereo-Cell），通过凝血块中凝血相关因子的表达特征，将无脊椎动物体内的特定血细胞亚型定义为血小板的潜在祖先类群。本研究阐明了免疫系统演化过程中吞噬作用的古老保守特征，并首次对血小板的起源作出了特异性界定。