S1PR1 and inflammatory bowel disease: Suh et al. have reported that S1PR1, S1PR2, and S1PR4 were upregulated in intestinal biopsies from IBD patients when compared to healthy controls [69], while Abarca-Zabalía et al. have shown a downregulation of the S1PR1 receptor in circulating CD4+ lymphocytes from CD patients [70].