Marker gene identification and functional characterization of dendritic cells (DCs)-like in turbot (Scophthalmus maximus).

Dendritic cells (DCs) are professional antigen-presenting cells that connect innate and adaptive immunity; however, the morphological and functional characterization of DCs-like in turbot (Scophthalmus maximus) remains undefined. In this study, we identified CD209a as a highly expressed marker gene for turbot DCs-like, featuring a conserved C-type lectin (CLECT) domain. A polyclonal antibody targeting the extracellular CLECT domain of CD209a enabled the isolation of CD209a+ DCs-like from splenic leukocytes. Morphological and ultrastructural analyses revealed that CD209a+ cells have relatively large dumbbell-shaped nuclei, pseudopodia-like membrane protrusions, and abundant intracellular vesicles and mitochondria. Functionally, we revealed the transcriptional profile of turbot DCs-like changed over the course of infection through single-cell transcriptomic data reanalysis and in vivo gene expression verification, with enrichment of antigen presentation at 3 dpi, immune defense at 7 dpi, and damage repair at 14 dpi. In addition, the abundance of turbot CD209a+ DCs-like increased dynamically after bacterial infection, supporting the involvement in host immune responses. Collectively, these findings advance our understanding of teleost DCs-like through characterizing their functional dynamics during bacterial infection, providing a critical evaluation parameter and theoretical basis for optimizing vaccine-induced immunity in aquaculture.