ABSTRACT
Lectins play important role in innate immunity of animals. The affinity of the natural haemagglutinin of the giant freshwater prawn Macrobrachium rosenbergii towards vertebrate erythrocytes and its level with relation to sex, size and moult stages were studied. The strongest agglutinating titres in haemolymph of prawns were marked against guinea pig, chicken, Clarias batrachus, and rabbit erythrocytes, and the weakest towards cattle, dog, horse and goat erythrocytes. A moderately agglutinating titre was evident in duck and human erythrocytes. The haemolymph of adult, male or intermoult stage prawns weighing more than 100 g had the highest haemagglutinating activity as compared to their respective counterparts with varied responses observed towards various erythrocytes.