Sponge aggregation factor: in situ localization by fluorescent monoclonal antibody techniques.
The aggregation factor (AF) from sponges mediates a heterophilic interaction of homologous cells. Applying electron microscopical means, we succeeded only very rarely in identifying the 90 S AF particle in tissue sections from Geodia cydonium. By means of a fluorescent antibody technique, we have now localized the cell binding domain of the AF in situ. Previous studies in this laboratory have led to the identification of the 47-kDa cell binding protein of the AF, using the monoclonal antibody (mab) 5D2-D11 [Gramzow M, Bachmann M, Zahn RK, Uhlenbruck G, Dorn A, Müller WEG, J Cell Biol, 102: 1344-1349, 1986]. This mab and mab 7D5, directed against a 92-kDa protein in the AF complex, were chosen for the fluorescent studies. By using mab 5D2-D11, the plasma membranes of cells from different regions in the sponge could be brightly stained. However, mab 7D5 reacted only very weakly with the sponge surfaces. By applying the immuno-blotting technique it was furthermore demonstrated that the cell binding protein is present both in the associated form with AF complex and in a free state. Moreover, it was established that the 47-kDa binding protein is not present in homologous glycoconjugates, lectin, or collagen; these components are known to be involved in cell-matrix interaction.
D000818:Animals; D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D002449:Cell Aggregation; D002462:Cell Membrane / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D008854:Microscopy, Electron; D011161:Porifera / Q000378:metabolism* / Q000648:ultrastructure; D011506:Proteins / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D011506:Proteins; C013065:cell aggregation factors