Innate Immune Responses of Skin Mucosa in Common Carp () Fed a Diet Supplemented with Galactooligosaccharides.

Galactooligosaccharides (GOS) are well-known immunomodulatory prebiotics. We hypothesize that GOS supplemented in feed modulates innate immune responses in the skin-associated lymphoid tissue (SALT) of common carp. The aim of this study was to determine the impact of GOS on mRNA expression of the immune-related genes in skin mucosa. During the feeding trial, the juvenile fish (bodyweight 180 ± 5 g) were fed two types of diet for 50 days: control and supplemented with 2% GOS. At the end of the trial, a subset of fish was euthanized (n = 8). Skin mucosa was collected, and RNA was extracted. Gene expression analysis was performed with RT-qPCR to determine the mRNA abundance of the genes associated with innate immune responses in SALT, i.e., acute-phase protein (CRP), antimicrobial proteins ( and ), cytokines (, , , , and ), lectin (), lyzosymes ( and ), mucin (), peroxidase (), proteases ( and ), and oxidoreductase (). The geometric mean of and was used to normalize the data. Relative quantification of the gene expression was calculated with ∆∆Ct. GOS upregulated ( ≤ 0.05) and ( ≤ 0.05), and downregulated ( ≤ 0.01). We conclude that GOS modulates innate immune responses in the skin mucosa of common carp.