Combined transcriptome and function analyses of peripheral blood white cells highlight the disease-resistant mechanism of CD79a/CD79b in Chinese tongue sole (Cynoglossus semilaevis).

Peripheral blood white cells are a vital component of the immune system and serve an important anti-bacterial function in teleosts; however, the molecular mechanism of peripheral blood white cells and B lymphocyte marker genes (CD79) has not been resolved in these fish. Therefore, peripheral blood white cells were isolated from Chinese tongue sole (Cynoglossus semilaevis) and stimulated with LPS for 6 h and 12 h to identify differentially expressed genes enriched in immune-related pathways under stimulation. A protein interaction map of the DEGs was constructed, identifying several immune-related genes, including CD79, Myd88, and TLR5. Within the immunological function of CsCD79, CD79 consists of two chains, CD79a and CD79b, which are linked through disulfide bonds or non-covalent interactions across species. Specifically, CD79 initiates intracellular signaling in B-cell receptor pathways, activates downstream processes, and plays a crucial role in B-cell development, organismal aging, and immune regulation. Notably, CD79 mRNA was predominantly expressed in the kidneys, spleen, and gills. Infection experiments revealed elevated expression levels of CD79 across all immune tissues at different time points, with disease-resistant strains exhibiting higher expression than susceptible strains. Live cell counts after three, nine, and 12 h of bacterial stimulation demonstrated stronger antibacterial function against Edwardsiella tarda and Vibrio harveyi when CD79 plasmids were transfected into HEK293T cells. This study systematically revealed the important role of CD79a/CD79b in bacterial disease resistance at the transcriptome and gene level. Results provide new ideas and molecular markers for preventing and controlling diseases in teleosts and underscore vaccine development for the Chinese tongue sole, consequently promoting the healthy and sustainable development of the mariculture industry.