Properties of sea urchin coelomocyte agglutinins

We examined some biological activities of a 200-kDa glycoprotein, referred to as Paracentrotus lividus vitellogenin, contained both in the coelomic fluid and in a subpopulation of coelomocytes called «colourless spherula cells». Cell-free coelomic fluid, coelomocyte lysate and supernatant obtained after coelomocyte washings were assayed for hemagglutinating activity. All samples agglutinated rabbit erythrocytes in a calcium-dependent way. The comparison between the electrophoretic patterns of erythrocyte lysates, before and after incubation with the coelomic fluid, revealed that a 200-kDa band was obtained from membranes of agglutinated erythrocytes. In addition, polyclonal antibodies against 200-kDa glycoprotein from sea urchin embryos used in Western blot analysis recognized the 200-kDa glycoprotein only when erythrocyte lysates previously incubated with coelomic fluids were assayed. These results suggest that the 200-kDa glycoprotein could be an agglutinin, present in the coelomic fluid and released by coelomocytes during stress conditions.