Systematic Review of Structural and Immunological Features of Mollusk Toll-like Receptors in Aquaculture Context

Hongyu Li^1*Xianwei Li²Yunhuan Zhu¹Jialu Xu¹Qingzhi Zhao¹Chen Xintong¹Yijie Zhang¹Ling Zhao¹Yutong Chen¹Ruiqi Weng¹Keda Chen^1*

• ¹Zhejiang Shuren University, Hangzhou, China
• ²Other

Toll-like receptors (TLRs) are a class of transmembrane proteins widely present in various animal species, playing essential roles in development and immune defense. Unlike vertebrates, which possess a complex immune system with adaptive immunity, mollusks rely solely on innate immune mechanisms, making these systems crucial for pathogen defense and environmental adaptation. While TLRs have been extensively studied in vertebrates, especially in mammals and fish, research in mollusks remains limited. Despite evidence of their broad distribution and structural diversity, the signaling pathways and functional roles of mollusks' TLRs are still not well understood. Although there are significant differences in the homology and function of TLRs between vertebrates and invertebrates, studies on vertebrate TLRs have provided valuable references for further exploring TLRs in mollusks. This systematic review summarizes the structural characteristics of TLRs in mollusks, explores their tissue-specific expression patterns, domain composition, and immune functions, and analyzes the bioaccumulation of environmental pollutants in mollusks. Finally, the disease prevention and control as well as ecological applications of the TLR in mollusks were discussed. Ongoing research on molluscan TLRs will yield important insights into species-specific immune strategies and foster progress in comparative immunology.