The immune system’s function is to maintain biological individuality, therefore, its main activity is to differentiate and eliminate all foreign material from its tissues.

Shrimp, like the rest of the crustaceans and unlike vertebrates, do not have immune organs, nor do they have acquired immunity, nor immunological memory.

Therefore, as they do not have a specific immune response against infectious agents, they have developed a complex, efficient and highly developed non-specific defensive system (innate immunity) made up of:

• Physical Barriers => exoskeleton that covers it externally and peritrophic membrane that surrounds the food bolus to protect the epithelium of the digestive system.
• Active Response => constituted by hemostatic mechanisms, cellular and humoral response.

The cellular response is mediated by hemocytes (circulating immunoactive cells), they possess cytotoxic capacity and intercellular communication that facilitates the functions of coagulation, recognition, phagocytosis, melanization, nodule formation and encapsulation.

The humoral response includes several plasmatic components (antimicrobial peptides, histones, lysosomal enzymes, lipopolysaccharides, glycan recognition proteins), the prophenoloxidase system, and the coagulation cascade that favors the destruction of pathogens.

Immune reactions are activated by pathogen-associated molecules, for example, LPS and bacterial peptidoglycans, fungal beta-glucans, and viral double-stranded RNA. The subsequent response is mediated by cellular and humoral mechanisms, that act in an integrated way, protecting them against the invasion of microorganisms and parasites, thus guaranteeing their bodily and homeostatic integrity.

Although there is no homology with the acquired immune system of vertebrates, it appears that the cellular immune system in these organisms has short-term memory.