Promoting activity of extracellular materials on sponge cell reaggregation.

INTRODUCTION It has long been known that sponge cells exhibit specific reaggregation (Wilson, 1907), manifested by the production from mixed cell suspensions of separate aggregates containing cells originating from one species only. A possible mechanism for this process is the specific adhesion of cell surfaces. Humphreys (1963) and Moscona (1963) showed that prolonged washing of sponge tissues with a Caand Mg-free sea-water medium yielded cells unable to reaggregate at low temperature. However, the supernatant fluid from this washing procedure contained a labile component that restored the capacity of the cells to reaggregate in the presence of divalent cations at low temperatures. Moreover, this activity was species specific in the system Microciona prolifera/ Haliclona oculata inasmuch as the supernatant fluid from Microciona cells would cause Microciona aggregates alone to be formed from a MicrocionajHaliclona cell mixture, whereas Haliclona supernatant fluid would selectively promote Haliclona aggregation. It has been reported by MacLennan (1963) that the antigenic character of the sponge cell surface is dominated by specificities which are shared with heteropolysaccharide substances that can be extracted directly from sponges. Since the selective promotion of reaggregation (Humphreys, 1963; Moscona, 1963) implies a recognition, by the extracellular product, of a complementary cell surface component in homologous cells, it can be argued that the specific carbohydrate antigens of the cell surface function as such complementary components. As a first stage in the study of this postulated interaction of extracellular reaggregation-stimulating factor and cell surface, we have examined sponges of known serological surface character for their ability to produce substances with reaggregation stimulating activity.