The high expression of CEACAM1 in kidney and liver was examined at higher magnification. As seen in Fig. 5A -B, the expression pattern for human CEACAM1 is identical to murine CEACAM1, but more intense. The pattern is consistent with the highest levels of expression in proximal tubules (less open lumen) and the lowest in distal tubules (more open lumen). In all cases the staining is on the luminal surface of the renal tubules. CEACAM1 is also expressed on the luminal surface of epithelial cells of the Bowman's capsules surrounding the glomeruli in the kidney (arrow, Fig. 5B ). In the case of the liver, the expression pattern of both murine and human CEACAM1 in the transgenic animals is confined to the bile canaluculi (Fig. 5D-E) . This expression pattern has been described previously [40] and suggests the possibility that the mechanism of insulin clearance by CEACAM1 [39] may be related to the function of bile canaliculi.