CELLULAR DEFENSE-MECHANISMS IN C-CAPITATA - RECOGNITION AND ENTRAPMENT OF ESCHERICHIA-COLI BY HEMOCYTES

The mechanism of recognition of foreignness and entrapment of invaders by the immune system of insects is unknown. In this report using hemo cyte monolayer preparations and biochemical analysis we demonstrate th e requirements for recognition of E. coli in vitro, their entrapment b y hemocytes, and nodule formation. A model system consisting of an iso lated hemocyte protein (47 KDa), isolated hemocyte tyrosinase, isolate d hemocytes, tyrosine, and E. coli was used to obtain these results. T he 47 kDa polypeptide has the ability to form adducts with tyrosine de rivatives generated by the action of tyrosinase and to attach to the E . coli surface. The latter process lakes place independently of tyrosi nase activity. When the E. coli-47KDa protein complex was overlaid on hemocyte monolayers followed by tyrosine and tyrosinase or vice versa, the bacteria were entrapped by hemocytes. The same results were obtai ned when the monolayers were overlaid with 47 KDa protein, followed by E. coli-47 KDa protein complex and then tyrosine and tyrosinase. The same experimental procedure in test tubes resulted in nodule formation . These results permit us to propose that the most likely explanation for the entrapment of E. coli to hemocytes and the formation of nodule s is the production of E. coli-47 KDa complexes, and their crosslinkin g through a quinone intermediate generated by the action of tyrosinase on hemocytes. (C) 1994 Wiley-Liss, Inc.