Transcription of selected immune-related genes in spleen cells of cod, Gadus morhua following incubation with alginic acid and β-glucan

The stimulatory effects of alginic acid and β-glucan on the transcription of selected immune-related genes in the spleen of Atlantic cod, Gadus morhua were evaluated in vitro. Spleen cells were incubated with 100μgml ^-1 of the test substances and the transcription levels of the selected genes related to antibacterial defense, inflammation, antioxidant defense, and glucose metabolism were determined at 3- and 24-h post-incubation. G-type lysozyme, interleukin-8 (IL-8), Cu, Zn-superoxide dismutase (Cu, Zn-SOD) and glucose transporter-1 and -4 (GLUT-1 and -4) genes were the early responders to the test substances as shown by their increased expression levels at 3-h post-incubation. Interleukin-1β (IL-1β) and GLUTs 2 and 3 showed significantly high levels of expression at 24-h post-incubation with the test substances and these genes could be the late responders. The expression levels of the bactericidal/permeability-increasing protein/lipopolysaccharide-binding protein (BPI-LBP) and catalase were significantly upregulated in cells incubated with β-glucan but not with alginic acid at 24-h after exposure. Most of the genes studied, except Cu, Zn-SOD and GLUT-1 had enhanced transcription levels at 24-h post-incubation with β-glucan. In contrast, the expression of most of the genes in cells incubated with alginic acid, returned to the pre-incubation transcription levels by 24h. Thus both alginic acid and β-glucan are able to differentially enhance the transcription of the selected immune-related genes in the spleen cells. This information could be valuable for further practical studies that aim to test these immunostimulants in fish.