Two CC motif chemokine 20-like genes differentially regulate leukocyte migration and survival via CC chemokine receptor 6 in ayu (Plecoglossus altivelis).

Chemokine ligand 20 (CCL20) is a key mediator of inflammatory and homeostatic responses in mammal, acting through its receptor CC chemokine receptor 6 (CCR6). However, its functional roles in teleost fish remain poorly defined. In this study, we identified two CCL20-like genes (PaCCL20l1 and PaCCL20l2) from ayu (Plecoglossus altivelis). Phylogenetic analysis confirmed their classification within the CCL20 subgroup. Tissue distribution analysis revealed ubiquitous expression of both genes, which were significantly upregulated in multiple tissues (liver, spleen, head kidney, gill, skin, and intestine) following infection with Vibrio anguillarum, albeit with distinct expression profiles. We produced the recombinant mature peptide of PaCCL20ls (rPaCCL20l1 and rPaCCL20l2) and generated specific antibodies. Functional assays demonstrated that both rPaCCL20l1 and rPaCCL20l2 exhibit chemotactic, and anti-apoptosis activities, but with differing cell specificities. rPaCCL20l1 attracted lymphocytes and neutrophils and inhibited lymphocyte apoptosis. In contrast, rPaCCL20l2 attracted monocytes/macrophages (MO/MΦ), lymphocytes, and neutrophils, and suppressed apoptosis in both MO/MΦ and lymphocytes. Crucially, neutralizing PaCCR6 completely abolished all effects of both rPaCCL20l1 and rPaCCL20l2. In conclusion, our findings demonstrate that PaCCL20l1 and PaCCL20l2 play pivotal but distinct roles in ayu immunity by modulating leukocyte recruitment and survival via PaCCR6 pathway.