TGFB1 and inflammatory bowel disease: One study examining mucosal cytokine expression in GSDs diagnosed with either ARE or IBD and healthy dogs using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) showed significantly higher mucosal mRNA expression of IL-2, IL-5, IL-12p40, TNF-α, and TGF-β1 in dogs with CIE than in healthy controls (79).