Granzyme B secreted by T cells is involved in anti-bacterial immune response of tilapia

Secreted by natural killer cells and cytotoxic T lymphocytes, Granzyme B is involved in regulating the adaptive immune response in vertebrates and plays a pivotal role in resisting virus invasion and removing pathogens. Although it had been extensively studied in mammals, the involvement of Granzyme B in adaptive immune response of early vertebrates remained elusive. In this study, we investigated the Granzyme B in Oreochromis niloticus (OnGrB), found that its function domain was conserved. Additionally, OnGrB was widely expressed in various tissues and could respond to T-cell activation in vitro at the transcriptional level. Furthermore, we prepared the recombinant OnGrB (rOnGrB) as an immunogen to develop a mouse anti-OnGrB monoclonal antibody (mAb). Using this anti-OnGrB mAb as a tool, we explored the expression of OnGrB in the adaptive immune response of tilapia. Our findings revealed that T cell was a significant source of OnGrB production, the expression of OnGrB at the protein level and the proportion of OnGrB