Although numerous antibodies are commercially available against human and rodent α-TTP, no specific antibody can be found on the market to be used in sheep studies. Therefore in this study, for the first time, a specific McAb was prepared for the detection of the ovine α-TTP protein and also for use in further studies. Our sheep α-TTP-specific McAb, named S16, proved to be both highly sensitive and specific and was able to detect sheep α-TTP in different immunoassays suggesting its potential usefulness for targeted applications. By means of the S16 antibody, immunohistochemical analyses were carried out to determine the localization of the α-TTP protein in sheep liver, as well as the expression levels of this protein in response to different levels of vitamin E supplementation. In line with previous reports, sheep α-TTP was highly expressed in the liver and showed predominantly cytosolic localization. However, it can be noted that a region surrounding the venule was not stained. Kaempf-Rotzoll et al. (2003) also reported that the endothelial cells lining the hepatic venule and the sinusoids were not stained, as well as the scattered phagocytic Kupffer's cells, suggesting specific localization of α-TTP to the cuboidal hepatocytes in human liver. The reasons for this unique distribution of α-TTP in liver are still unclear and warrant further investigations. Besides the liver, we also found that sheep α-TTP was expressed in the cytoplasm of heart, spleen, lung and kidney cells, but not in striated muscle and testicular tissues (data not shown). Furthermore, immunohistochemical analyses showed no statisticall significant difference of the sheep α-TTP expression levels in response to vitamin E supplementation