A lipopolysaccharide-binding hemagglutinin with specificity for acetylated aminosugars in the serum of the hermit crab Diogenes affinis (Henderson).

A naturally occurring hemagglutinin was detected in the serum of the hermit crab Diogenes affinis, and its erythrocyte (RBC) binding activities, physicochemical properties, and carbohydrate binding specificity were characterized. Both the hemagglutination profile and the pattern of cross-reactivity of the serum with different RBC types in cross-adsorption tests suggested a strong affinity of the serum agglutinin for rat RBC. Further analysis revealed that the agglutinin was specifically dependent on Ca2+ for its hemagglutinating activity and reversibly sensitive to EDTA. The activity was found to be stable between pH 6.0 and 7.5, heat-labile, and completely precipitable by ammonium sulphate or TCA, suggesting the proteinaceous nature of the serum agglutinin. In hemagglutination-inhibition assays, the serum agglutinin of D. affinis showed a distinct and unique specificity for acetyl group-containing carbohydrates and glycoprotein. Furthermore, the hemagglutinating activity of the serum agglutinin was also inhibited by lipopolysaccharide from Salmonella abortus equi, which might indicate a significant role of humoral agglutinin in the immune response of crustaceans against bacterial infection.