A naturally occurring hemagglutinin molecule detected in the hemolymph of black clam Villoritta cyprinoides was able to agglutinated various mammalian erythrocytes. Reduction of activity was obtained when the animals were treated with Cd and Pb. As the hemocyte play a vital role in the innate immunity, this findings strongly confirmed that the heavy metals such as Cd and Pb affects the immune function of V. cyprinoides.