Cell adhesion molecules and antioxidative enzymes in a crustacean, possible role in immunity

The question as to how the immune defence of an invertebrate animal is init iated and coordinated has largely been unanswered. This short review focuse s on recent discoveries about crayfish hemolymph proteins, which may play r oles in cell adhesion events leading to initiation of phagocytosis and enca psulation. Focus will also be made on anti-oxidative enzymes that may parti cipate in the production of reactive oxygen compounds used in the destructi on of engulfed or encapsulated parasites. Peroxinectin is stored in semi-gr anular and granular hemocytes and released concomitant with activation of p rophenoloxidase (proPO). It is a cell adhesion protein, enhancing phagocyto sis and encapsulation and triggers degranulation. It is also a peroxidase, belonging to the same protein family as mammalian myeloperoxidase. Peroxine ctin binds a 90-kDa peripheral cell surface superoxide dismutase (SOD) of c rayfish blood cells. Integrins are transmembrane proteins present on crayfi sh hemocytes and commonly known to be acting as cell adhesion receptors in many events. After its release and activation, peroxinectin may opsonize fo reign surfaces where it is recognized by integrins on the hemocyte. This ca n be a starting point for phagocytosis or encapsulation. Peroxinectin and e xtracellular SOD (EC-SOD) may then cooperate during a respiratory burst to destroy an ingested or encapsulated parasite. (C) 1999 Elsevier Science B.V . All rights reserved.