Our interest in Marine Biomedicine is centered on understanding the innate immune system of the purple sea urchin, Strongylocentrotus purpuratus. Efforts are focused on the functions of the immune cells, or coelomocytes (cells found in the coelom) that become activated in response to infection or injury. We have identified a number of genes that are upregulated in activated coelomocytes in response to lipopolysaccharide (LPS), other pathogen associated molecular patterns, and heat killed Vibrio. These include homologues of the complement cascade and a family of genes called 185/333.