IMMUNOHISTOCHEMICAL LOCALIZATION OF POLYSIALIC ACID IN TISSUE-SECTIONS - DIFFERENTIAL BINDING TO POLYNUCLEOTIDES AND DNA OF A MURINE IGG AND A HUMAN-IGM MONOCLONAL-ANTIBODY

For immunolocalization of α(2-8)-linked polysialic acid, which forms part of the neural cell adhesion molecule (N-CAM), two monoclonal antibodies, MAb735 and IgM(NOV), were employed. Both antibodies have previously been shown to bind the extremely low immunogenic capsular polysaccharide of group B meningococci, which also consists of α(2-8) polysialic acid, but not to other, even closely related forms of polysialic acid. Despite the identical polysaccharide specificity of these two MAb, we observed marked differences of the staining pattern in tissue sections. We showed that these differences in immunostaining were due to the crossreactivity of IgM(NOV) with polynucleotides and DNA. MAb735, however, was shown to react exclusively with α(2-8) polysialic acid. Moreover, the specificity of MAb735 proved to be unique among eleven other MAb directed against various bacterial polysaccharides, as it was the only one unreactive with polynucleotides. Thus, MAb735, the only IgG type mouse monoclonal antibody to polysialic acid thus far reported, can be considered a specific probe for the unambiguous detection of α(2-8) polysialic acid in tissue sections, and should therefore help to further elucidate the role of polysialic in developmental processes.