In vivo immune response of major immunocompetent organs in Indian major carp, Cirrhinus mrigala upon infection with Aeromonas hydrophila

Abstract

Indian major carp, Cirrhinus mrigala (Bloch, 1795) (Cyprinidae) were challenged with Aeromonas hydrophila to ascertain the efficacy of immunocompetent organs, head kidney and spleen. The experimental design consisted of control samples, fishes sacrificed after 7 days (acute toxicity study) and 30 days (chronic toxicity study). The histopathology, oxidative stress and assessment of cell death have been characterized. Histopathology revealed changes in splenocytes and haemopoietic cells of head kidney. Cell death was reported in conjunction with increase in the melanomacrophage centres. Flowcytometric analysis after 7 days revealed increase in ROS production with a concomitant rise in apoptosis in both organs. After 30 days, ROS generation showed an approximate 5.55 fold increase in the DCF mean peak in comparison to 15.84 fold increase (7 days) in head kidney, while spleen recorded 2.37 fold increase (7 days) which had decreased to 1.43 fold after 30 days. Apoptotic cells in head kidney was 4.92 % (7 days) while after 30 days, it reported only 0.64 %. In spleen, recovery led to a 0.96 % apoptosis in comparison to a 2.42 % observed after 7 days. This work presents an insight into the immunocompetency of both organs that control the innate immune responses in fish.