Lectin binding sites and immunocytochemical characterization of normal pleural mesothelium

20 specimens of normal pleural mesothelium were investigated with six lectins using isolated cells and tissue specimens as well as two different fixation techniques (glutaraldehyde and formaldehyde) and 10 monoclonal antibodies (MAb) on cytologic preparations only. Lectin binding sites for ConA, WGA, and PNA were present in all cases, whereas binding sites for the lectins HPA, SBA, and UEA-I could never be found. There was no staining difference with the two preparation and fixation techniques proving that they may be used to compare directly histologic and cytologic studies. Ten of fourteen histologic specimens were positive for the blood group antigen Lewis(y), three of them were positive for the antigen Lewis(b), all fourteen specimens were negative for Lewis(a) and Lewis(x). In all cases, mesothelial cells expressed ICAM1 and pancytokeratin. The antibodies against EMA, CEA, CD24, CD15, CD20, CD5, and HEA125 showed no reaction in mesothelial cells. Because HPA, UEA-I, SBA as well as CEA and HEA125 react in a high percentage with adenocarcinomas, non reactive cells of pleural effusions negative with these markers may be confidentially considered to be mesothelial in origin.