A comparative study on the immune response in the head and trunk kidney of yellow catfish infected with Edwardsiella ictaluri

The teleost kidneys are anatomically divided into head kidney and trunk kidney, each performing distinct physiological functions. Although previous research has elucidated the role of the head kidney in immune responses, there is a paucity of literature on the comparative studies of the head and trunk kidney response to bacterial infection. Therefore, an Edwardsiella ictaluri infection model of yellow catfish was constructed to investigate and compare the immune responses between the two kidney types. The findings indicated that E. ictaluri infection induced significant pathological changes in both the head and trunk kidney. Despite variances in structure, both the head and trunk kidney of yellow catfish exhibit robust immune responses following E. ictaluri infection. Unexpectedly, the up-regulation level of IgM was found to be higher in the trunk kidney compared to the head kidney. Additionally, both the IgM(+) and IgD(+) B cells were increased after bacterial infection. This research elucidates the parallels and distinctions in immune functions between both the head and trunk kidney in fish, enriching the immune theory of the fish kidney, and also providing a theoretical basis for the immune response of teleost kidney against bacterial infections.