Immunomodulatory Effects of a Bioactive Compound Isolated fromDryopteris crassirhizomaon the Grass CarpCtenopharyngodon idella

In the present study, we investigated effects of compound kaempferol 3-a-L-(4-O-acetyl)rhamnopyranoside-7-a-L-rhamnopyranoside (SA) isolated fromDryopteris crassirhizomaduring immune-related gene expression inCtenopharyngodon idellahead kidney macrophages (CIHKM). The expression of immune-related genes (IL-1β,TNF-α,MyD88, andMx1) were investigated using real-time PCR at 2 h, 8 h, 12 h, and 24 h after incubation with 1, 10, and 50 μg mL−1of SA. Furthermore, fish were injected intraperitoneally with 100 μL of SA, and immune parameters such as lysozyme activity, complement C3, SOD, phagocytic activity, and IgM level were examined at 1, 2, and 3 weeks after injection. The differential expression of cytokines was observed after exposure to SA.IL-1βgenes displayed significant expression at 2 and 8 h after exposure to 1–10 μg mL−1of SA. SA also induced gene expression of cytokines such asMyD88,Mx1, andTNF-α. Furthermore, enhanced immune parameters in grass carp confirmed the immunomodulatory activity of SA. Interestingly, this compound has no toxic effect on CIHKM cells as tested by MTT assay. In addition, fish immunised with 10 μg mL−1of SA exhibited maximum resistance againstAeromonas hydrophilainfection. These results suggest that SA has the potential to stimulate immune responses in grass carp.