Diseases have emerged as a major constraint to the sustainable growth of aquaculture and diseases are linked to environmental deterioration and stress associated with farm intensification. The prevention and the control of diseases are now considered priorities for shrimp aquaculture in shrimp producing countries. Research in immune genomics has been a subject of only minor interest, particularly when compared to similar research in insects. Crustacean immunology is a key element in establishing strategies for disease control in shrimp aquaculture. Therefore, there is need to study about the immune system and its immune responses when pathogen invasion occurs. In crustacean's immunology, prophenoloxidase cascade plays the important role in the defense mechanism, to enhance the immune system of host and prevents the diseases through triggering of the humoral mediated immune pathway. The prophenoloxidase (ProPO) -activation pathway is a phenoloxidation cascade comprising of patternrecognition proteins, several serine proteases, their inhibitors and terminates with the zymogens, ProPO. Serine proteases can cleave the ProPO to generate the active enzyme, phenoloxidase.