IL-15 is an important growth and activator factor for mucosal intraepithelial lymphocytes [17], and it has also a marked anti-apoptotic function, as previously shown [18].Quite recently, it has been demonstrated a higher expression of IL-15 in IBD colonic mucosa, thus suggesting a role of this cytokine in the IBD pathogenesis [19, 20]. The gene discussed is IL15; the disease is inflammatory bowel disease.