A model system mimicking the superoxide generative reaction in insect haemolymph plasma has been developed. The superoxide generative system in the plasma consists of at least two factors of low (LMF) and high molecular weight (HMF). LMF and HMF are contained in a supernatant of heat-treated (100 degrees C 2 min) plasma (LMF sample) and dialyzed plasma (MW-100,000 cut off, HMF sample) respectively. Their mixture yields superoxide production. In the present study, surfactants were demonstrated to substitute for the HMF. Since surfactants were shown to mediate superoxide generation, in the mixture, with a LMF sample above their critical micellar concentrations, the micellar structure was suggested to be essential for function. A liposome suspension, a cellular membrane model, was able to substitute for the HMF sample to yield superoxide generation. Preliminary characterizations of the LMF were done by a reversed phase column, ion exchangers, and gel filtration using HMF and the newly developed surfactant system.