Fig. 4. (A) Immunoblot analysis of cadherin-catenin expression in the human thymus. Protein extracts of human thymic tissue were separated on 10% polyacrylamide gels and transferred to nitrocellulose filters. After blocking, the filters were divided into five lanes and incubated with antibodies against E-cadherin, P-cadherin, -catenin, ß-catenin and -catenin. After colorimetric development, the 120 kDa bands of E-and P-cadherin (lane 1 and 2), the 102 kDa band of -catenin (lane 3), the 94 kDa band of ß-catenin (lane 4) and the 86 kDa band of -catenin (lane 5) were detected in the thymic extracts. Partial degradation products were observed for E-cadherin and ß-catenin. The positions of 120 and 94 kDa are indicated on the left side. (B) Co-immunoprecipitation of cadherins and catenins isolated from human thymus. Cell lysates of freshly isolated thymic tissue were immunoprecipitated (IP) with monoclonal antibodies against E-cadherin (lanes 1,6) and -catenin (lanes 4,9), with polyclonal antisera against -catenin (lanes 2,7) and ß-catenin (lanes 3,8) or without antibody (lane 5). The precipitated immune complexes were immunoblotted with antibodies against E-cadherin (lanes 1-4) and ß-catenin (lanes 5-9). Co-precipitation of E-cadherin with the different catenins and of ß-catenin with -catenin and E-cadherin, but not with -catenin, revealed functional cadherin-catenin complexes. (C) Immunoblot analysis of cadherin-catenin expression in thymic epithelial cells. Protein extracts of isolated thymic epithelial cells were separated on 10% polyacrylamide gels. After transfer to nitrocellulose, the filters were incubated with antibodies against E-cadherin (lane 1), P-cadherin (2), -catenin (3), ß-catenin (4) and -catenin (5). After colorimetric development, specific bands for all analysed antigens were detected. Partial degradation products were observed for ß-catenin and -catenin (lane 4 and 5). The positions of 120 and 86 kDa are indicated on the left side.