The early disease onset shortly after weaning appears to contrast with humans, in which the majority of early-onset IBD patients have an age of ~10 years at diagnosis.50 The ‘weaning reaction’ of the immune system in response to concomitant microbiota alterations is accompanied by an upregulation of TNF, which is thought to be a disease trigger in the TNFΔARE animal and probably contributes to the early disease onset in the swine model.51 As in mice the reasons why only about 50% of heterozygous porcine mutants show disease manifestations remain to be elucidated. This evidence concerns the gene TNF and inflammatory bowel disease.