Aggregation of sponge cells: immunological characterization of the species-specific Geodia aggregation factor.

Antibodies were raised against the purified aggregation factor from Geodia cydonium in order to clarify its function during cell aggregation in the homologous and heterologous system. These antibodies inhibited only cell aggregation in the homologous Geodia system and were inactive in the heterologous Tethya lyncurium system. These findings directly indicated that the species-specific reaggregation of sponge cells was initiated by the soluble aggregation factor as already assumed in earlier studies. The amount of neutralizing antibodies was determined by a precipitation reaction with the antigen in capillaries and by microdiffusion. By using the latter technique we got evidence that the Geodia aggregation factor contained a component that was antigenetically related to a galactose-specific lectin present in Geodia cydonium.