Expression profile of cytokine genes in the common carp species Cyprinus carpio L. following infection with Aeromonas hydrophila

In the current study, the expression levels of interleukin (IL)-1 beta, IL-10, tumor necrosis factor-alpha (TNF-alpha), CC-chemokine and CXC-chemokine were examined in head kidney (HK) leukocytes of common carp Cyprinus carpio L. following experimental infection with Aeromonas hydrophila and compared with those of carp treated with formalin-killed A. hydrophila. The expression of IL-1 beta was highest at 8 h post-infection (p.i), while the levels of IL-10 increased 8 h p.i and exhibited the highest gene expression levels. The levels of TNF-alpha, CC- and CXC-chemokine were only slightly modulated following A. hydrophila infection. Therefore, we suggest that in carp, IL-10 behaving as inflammatory cytokine and controlling the expression level of other inflammatory cytokines early after bacterial infection. The levels of TNF-alpha, CC- and CXC-chemokine were only slightly modulated following A. hydrophila infection. In contrast, it was noted that in HK leukocytes of carp treated with formalin-killed A. hydrophila, the expression levels of the measured cytokines were down-regulated at almost all time points. The results suggest that similar to mammals, a complex network of cytokines regulate the immune response of fish against pathogens.