This area requires further investigation and is particularly important in the case of mouse models that have been developed to look at health issues closely related to the human gut system including inflammatory bowel disease models in IL-2 and IL-10 KO mice [57], [58] that develop colitis in the presence of a gut microbiota [59], [60] and inbred mouse models used for studying drug metabolism and obesity [9], [11]. Here, IL2 is linked to obesity due to melanocortin 4 receptor deficiency.