Does the loss of Abcg8/sterolin-2 result in loss of Abcg5/sterolin-1 expression, as might be predicted from the genetic studies and more recently from the in vitro and in vivo expression studies? A robust antibody to mouse Abcg8/sterolin-2 is not currently available. However, three separate groups have developed rabbit polyclonal antibody to mouse Abcg5/sterolin-1. These three antibodies were used in Western blotting and immunohistochemistry experiments on the liver and intestine of Abcg8-/- mice. Western blotting of liver total membrane preparations using the three separately-developed anti-Abcg5/sterolin-1 antibodies showed different results. As has been previously published, Abcg5/sterolin-1 exists in two separate forms, the 'immature' 75 kDa protein and a fully glycosylated 'mature' 93 kDa protein [18,30]. Using the SC anti-Abcg5/sterolin-1 peptide antibody, a 75 kDa band is detected (Figure 5a). This antibody does not detect a 'mature' 93 kDa band in either wild-type or knockout animals nor is the 75 kDa band sensitive to either Endo-H or PNGaseF (lower panel shows same aliquots probed with anti-transferrin). The AMC antibody detects the 'mature' form of Abcg5/sterolin-1 in wild-type animals but not the knockouts. Interestingly, the 'immature' 75 kDa band is detected by this antibody but the band shifts with Endo-H and PNGase F treatment (Figure 5b). The UTSW antibody detects the 'mature' and 'immature' forms of Abcg5/sterolin-1 in wild-type animals but detects no forms in the knockout mouse (Figure 5c). What does hold true for all antibodies used against Abcg5/sterolin-1 is the detection of a 75 kDa band.