Progenitors of distinct lineages shape the diversity of mature type 2 conventional dendritic cells.

Conventional Dendritic Cells (cDC) are antigen-presenting cells comprising cDC1 and cDC2 subsets, responsible for priming naïve CD8+ and CD4+ T cells, respectively. Recent studies have unveiled cDC2 heterogeneity and identified various cDC2 progenitors beyond the common DC progenitor (CDP), hinting at distinct cDC2 lineages. By generating Cd300ciCre-hCD2R26tdTomato reporter mice, we identified a bone marrow pro-cDC2 progenitor exclusively generating cDC2 in vitro and in vivo. Single-cell analyses and multiparametric flow cytometry demonstrated that pro-cDC2 encompass myeloid-derived pre-cDC2 and lymphoid-derived pDC-like precursors differentiating into a transcriptionally convergent cDC2 phenotype. Cd300c-traced cDC2 had distinct transcriptomic profiles, phenotypes, and tissue distributions compared to Ms4a3CreR26tdTomato lineage-traced DC3, a monocyte-DC progenitor-derived subset that bypasses CDP. Mice with reduced Cd300c-traced cDC2 showed impaired humoral responses to a blood-borne antigen. We conclude that progenitors of distinct lineages shape the diversity of mature cDC2 cells across tissues. Thus, ontogenesis may impact tissue immune responses. Overall design: We performed single-cell RNA/ATAC (multiome) sequencing on Lin- B220- Flt3+ BM progenitor cells extracted from three CD300c-iCre-hCD2 R26tdTomato mice.常规树突状细胞（cDC）是一类抗原呈递细胞，包含cDC1和cDC2两个亚型，分别负责激活初始CD8+ T细胞与初始CD4+ T细胞。近期研究揭示了cDC2的细胞异质性，并在常见树突状细胞祖细胞（CDP）之外鉴定出多种cDC2祖细胞，提示存在不同的cDC2发育谱系。本研究通过构建Cd300c-iCre-hCD2 R26tdTomato报告基因小鼠，成功鉴定出一种仅可在体外与体内生成cDC2的骨髓前cDC2祖细胞。单细胞分析与多参数流式细胞术结果显示，前cDC2包含髓系来源的pre-cDC2以及淋巴系来源的pDC样前体细胞，二者均可分化为转录特征趋同的cDC2表型。与绕过CDP通路、源自单核细胞-树突状细胞祖细胞的Ms4a3Cre R26tdTomato谱系追踪DC3亚群相比，Cd300c标记追踪的cDC2具有独特的转录组特征、细胞表型与组织分布特性。当Cd300c标记追踪的cDC2数量减少时，小鼠针对血源性抗原的体液免疫应答出现受损。综上，不同发育谱系的祖细胞塑造了各组织中成熟cDC2细胞的多样性，因此发育起源可能影响组织免疫应答。整体实验设计：我们对来自3只Cd300c-iCre-hCD2 R26tdTomato小鼠的Lin⁻ B220⁻ Flt3⁺ 骨髓祖细胞进行了单细胞RNA/ATAC（多组学）测序。