Relative transcription levels of genes with significant differences between dietary groups. The dot plots for CD3ζ, MHC class II and TGF-β in the pyloric caeca (A) and CD3ζ, IgM and IgT in the distal intestine (B) show the transcript levels for each individual with mean for each group as obtained by real-time RT-PCR analysis. Transcript levels are presented relative to the mean of the fish oil group. Error bars represent standard error of the mean. a,bSignificant differences (ANOVA, P < 0.05) between dietary groups are denoted by different letters above the dot plots. FO = fish oil, OO = olive oil, RO = rapeseed oil and SO = soybean oil.