Cellular immunity in crustaceans and the proPO system.

The molecular mechanism of cellular immunity in arthropods has until recently been largely unknown, but with the development of a technique to isolate and handle the different blood cell types of crustaceans and with the purification of several proteins associated with the so-called proPO system of freshwater crayfish the processes have now begun to be better understood. In this article Mats Johansson and Kenneth Söderhäll discuss the function of the proPO system in cellular immune reactions in crustaceans and in particular the role of a protein with a molecular mass of 76 kDa, which has been shown to be involved in the communication between the different blood cell types of crayfish.